Soft material engineered synthetic polymer membranes: bridging design and application
Ashok K.
Pandey
*
Department of Nuclear and Radiochemistry, Kishinchand Chellaram College, HSNC University, Mumbai-400020, India. E-mail: ashok.pandey@kccollege.edu.in; akpandey.brns@gmail.com
First published on 28th October 2025
Abstract
Soft material-based synthetic polymer membranes are emerging as transformative platforms for energy, environmental, and healthcare technologies, attributed to their flexibility, tunability, and multifunctionality. These membranes are designed through two principal strategies, i.e. pore-filling and surface/interface engineering. Hydrogels could also be used, especially in biomedical applications, with fibre reinforcement to enhance mechanical stability. Pore-filled or “gel-in-shell” membranes incorporate hydrogels or functional soft materials within porous polymer matrices, combining chemical functionality with structural support. These systems enable the fast and selective transport of ions or molecules, finding applications in fuel cells, batteries, solar desalination, and water purification. Stimuli-responsive designs, where thermally, chemically, piezoelectric or optically sensitive polymers are grafted within or onto membrane pores, enable dynamic control over permeability, critical for smart drug delivery and adaptive filtration. Self-healing hydrogels, driven by dynamic bonding or ionic crosslinking, further enhance membrane longevity under operational stress. On the surface engineering side, functionalization via plasma treatment, graft polymerization, layer-by-layer assembly, molecular layer deposition, or mussel-inspired polydopamine coatings enables control over surface charge, hydrophilicity, and antifouling performance. Advanced materials such as MOFs and MXenes could also be incorporated in membrane designs to enhance functional properties. These engineered interfaces, such as surface patterning or nanofiber anchoring of the surface, are crucial for addressing challenges such as fouling, poor selectivity, and biocompatibility issues typically encountered in traditional membranes. Fibre-reinforced hydrogels further expand the application scope into biomedical systems, offering tissue-like mechanical resilience for tissue scaffolds, wound dressings, and wearable biosensors. This review highlights the integrated design of soft material-based membrane systems and their application across clean energy, sustainable water technology, environmental remediation, and biomedical fields. Such multifunctional membranes are central to next-generation technologies aligned with global sustainability goals.
 Ashok Pandey | Dr Ashok Pandey earned his M.Sc. degree in Inorganic Chemistry from Bundelkhand University and Ph.D. degree from Mumbai University and conducted postdoctoral research on synthetic polymer membranes at McMaster University, Canada. He worked as a Senior Scientist at the Bhabha Atomic Research Centre, a Senior Programme Officer at the Board of Research in Nuclear Sciences and a Professor of Chemical Science at Homi Bhabha National Institute. He has supervised seven doctoral students and authored 150+ research papers. His major research subject has been synthetic polymer membranes. At present, he is the Principal Scientific Advisor and Director, R&D Cell at HSNC University, Mumbai. |
Design, System, ApplicationSoft materials such as polymers, hydrogels, and elastomers are key to next-generation membrane technologies across water treatment, energy, and healthcare. Their inherent flexibility, high deformability, and functional adaptability support selective separation, fouling resistance, and stimuli-responsive behavior. However, their mechanical fragility limits standalone use. To overcome this, soft materials are integrated into rigid membrane systems through pore-filling, fiber reinforcement, and surface engineering. Pore-filling with hydrogels, deep eutectic solvents (DESs), or conductive polymers via in situ polymerization or grafting enhances membrane selectivity, durability, and responsiveness. Photopolymerization and controlled polymerization methods like RAFT and ATRP ensure tunable performance and scalability. These advanced membranes offer self-healing through dynamic bonds, smart gating via stimuli-responsiveness, and conductivity using polypyrrole or polyaniline, making them suitable for sensors, drug delivery, and electrochemical systems. Fiber-reinforced hydrogels mimic biological tissue mechanics and are employed in tissue engineering and wearable electronics. Surface and interface engineering techniques, such as plasma treatment, polydopamine coating, and molecular layer deposition, further optimize hydrophilicity, biocompatibility, and anti-biofouling properties. Surface patterning and integration of electrospun nanofibers onto synthetic polymer membranes are emerging strategies for engineering membranes with tailored functional performance, such as enhanced fouling resistance and flow-through adsorption during ultrafiltration. These hybrid designs enable multifunctional membranes tailored for sustainable water purification, bio-integrated systems, and next-generation energy devices, contributing to important UN Sustainable Development Goals. |
1. Introduction
Soft materials, characterized by elastic moduli below 10 MPa, are defined by their deformability and responsiveness to external stimuli, making them central to modern materials science.1 Polymers, gels, and elastomers exemplify this class, offering mechanical flexibility, tunable porosity, and diverse chemical functionalities.2 Their versatility supports applications across wastewater treatment,3,4 energy storage,5,6 agriculture,7,8 tissue engineering,9 food science,10 sensor development,11 self-healing cement,12 flexible electronics,13 and separation science.14,15 Despite these wide-ranging applications, the practical use of soft materials is constrained by several limitations, including limited mechanical robustness, susceptibility to degradation under fluctuations in pH, temperature, and humidity, and challenges in achieving long-term stability. Large-scale fabrication, reproducibility, and cost-effectiveness remain additional hurdles to industrial translation of the soft materials. Addressing these challenges requires the application of “molecular design & engineering” strategies, which allow rational tailoring of properties of soft materials at the molecular and supramolecular levels. Strategies such as immobilization within microporous membranes, anchoring onto surfaces to enhance interfacial stability, and reinforcement through crosslinking or incorporation of nanofillers or nanofibers have been shown to improve durability, mechanical strength, and functional longevity of soft materials. Together with hybridization, supramolecular assembly, and bio-inspired architectures, these approaches provide powerful pathways for engineering robust, scalable, and multifunctional soft materials.The adaptability of soft materials makes them especially promising for membrane engineering, where selective separation, controlled permeability, and long-term stability are essential. Membranes represent a core platform in processes related to water, energy and healthcare, with direct implications for the UN Sustainable Development Goals.16–18 Synthetic polymer membranes incorporating engineered soft materials have emerged as sustainable solutions for water purification, environmental remediation, energy generation, and healthcare. Their molecular-level tunability enables precise control over selectivity and transport, while their integration with synthetic polymer membranes enhances fouling resistance, mechanical robustness, and potential for stimuli-responsiveness. Anchoring soft materials into membrane architectures creates next-generation, high-performance membranes with superior adaptability and efficiency.
One of the most promising soft materials is hydrogel. Since hydrogels are biocompatible and adhere to tissues, they can be employed to deliver drugs or cells, for the regeneration of tissues, to enhance contrast during imaging, to protect tissues or organs during radiotherapy, to impart biocompatibility to medical implants, etc.19 Hydrogels are a tuneable platform for solar-powered desalination and water purification.20 Similarly, the desired ionic/electronic conductivity and rheological properties lead to many applications of hydrogels in wearable sensors and energy materials.21 Functional gel materials have immense potential for next-generation electrochromic devices and similar applications.22 Therefore, engineering of hydrogels to overcome their limitations is most widely explored. The major design strategies used to construct soft material-based membranes are fibre reinforcement, surface engineering, and pore-filling, as shown in Fig. 1. The surface engineering and pore-filling approaches involve porous rigid support host membranes, with the guest component being soft materials.23 Fibre reinforced hydrogels also have good mechanical properties without affecting the pristine properties of the hydrogels, and find extensive applications in tissue engineering and other biomedical applications.24
 | ||
| Fig. 1 Different fabrication strategies generally encountered in soft-material engineering to provide mechanical strength and tailor properties to targeted applications. | ||
2. Engineering of soft materials
The engineering of soft materials involves molecular designs to optimize performance for specific applications, combining the mechanical properties of the host substrate and the functional properties of the hydrogel. For example, the extent of crosslinking of polymer chains enhances structural cohesion, fibre reinforcement increases tensile strength, pore-filling and pore grafting improve density and functionality, while surface engineering provides external interactions. Depending upon the requirement of the targeted application, one of these approaches contributes to the development of high-performance soft material-based membranes with tailored mechanical properties for water treatment, biomedical, industrial, and myriad engineering applications. The different designs to provide the desired mechanical strength are shown in Fig. 2. | ||
| Fig. 2 Schematic illustration of the possible molecular engineering designs for providing mechanical strength to soft materials with different configurations. | ||
2.1. Pore-filling
Pore-functionalized synthetic polymer membranes are a class of advanced membranes and separators that have garnered significant attention due to their versatility and the potential to tailor them for various applications, including water purification, gas separation, chemical sensing, catalysis, and biomedical uses.23 These membranes are made by immobilizing the desired hydrogel in the pores of microporous membranes. These hydrogel composite membranes can be tailored to have controlled pore sizes, pore-in-pore structures, and a specific chemical composition, thereby enhancing their performance in various separation and filtration processes. These hydrogel-immobilised synthetic polymer membranes are constructed via pore-grafting or pore-filling in robust microporous membranes using various methods, such as in situ polymerisation of monomers or in situ crosslinking of preformed polymers. It is expected that the mass gain corresponding to the anchored hydrogel in pore-filling would be higher by in situ polymerization of monomers as compared to in situ crosslinking of preformed polymers, which is attributed to the higher solubility of monomers in the solvent as compared to preformed polymers. A key requirement for this type of membrane is that the guest component, hydrogel, is locked within the pores of the microporous host and remains stable during application over a longer period of time. The pore size and structure of these membranes can be finely tuned during the fabrication process, allowing for the selective separation of molecules based on their size, such as in the nanofiltration process. The structure of the pores may range from microporous to nanoporous, depending on the intended application. In these membranes, the guest component provides separation characteristics, and the host component, a microporous membrane, is responsible for mechanical containment. The concept of a pore-filled membrane is illustrated in Fig. 3. | ||
| Fig. 3 Schematic representation of the formation of pore-filled membranes. | ||
 | ||
| Fig. 4 Scanning electron micrographs of microporous host membranes composed of (a) poly(propylene) (PP), (b) poly(vinylidene fluoride) (PVDF), and (c) poly(ethersulfone) (PES). Image (d) shows the surface morphology of a pore-filled PP membrane prepared by in situ polymerization of 2-acrylamido-2-methyl-1-propane sulfonic acid (monomer), (3-acryloxypropyl)trimethoxysilane (spacer), and ethylene glycol dimethacrylate (crosslinker) [reprinted from ref. 26, Copyright 2013, with permission from Elsevier]. | ||
To understand the changes in pore-size distribution after pore filling, N-isopropylacrylamide (NIPA) was polymerized within the pores of a poly(propylene) (PP) host membrane via UV-induced polymerization.27 The resulting crosslinked poly(NIPA) microgel anchored within the PP membrane is expected to reduce both the porosity and pore diameter of the host membrane, depending on the extent of pore filling. The amounts of poly(NIPA) incorporated into the host membrane were 25 wt%, 50 wt%, and 100 wt%. These pore-filled membranes were characterized by capillary flow porometry (CFP).27 The flow rates across the dry membranes systematically decreased with increasing pore filling, indicating reduced porosity due to partial or complete obstruction of the pores. Pore-size distributions for the pore-filled membranes, obtained from analyses of the wet and dry CFP curves, are presented in Fig. 5. As seen in the figure, the 25 wt% poly(NIPA)-anchored membrane exhibited a broadened pore-diameter distribution on both sides compared to the pristine PP membrane, suggesting that partial pore filling perturbed the original pore structure of the host membrane. With higher degrees of pore filling (50 wt% and 100 wt%), the distributions became narrower, multimodal, and shifted toward smaller pore sizes. These results indicate that the pores of the host PP membrane were progressively filled as a function of mass gain. Notably, a mass gain as high as 200 wt% resulted in nearly complete pore blockage, as evident from the SEM image shown in Fig. 4.
 | ||
| Fig. 5 Comparison of pore-diameter distributions as a function of pore-filling by in situ UV polymerization of N-isopropylacrylamide along with a crosslinker N,N′-methylenebisacrylamide in the host poly(propylene) membrane [reprinted from ref. 27, Copyright 2012, with permission from Elsevier]. | ||
The functional properties of pore-filled membranes are primarily governed by the chemical composition of the hydrogel immobilized within the pores, rather than by the characteristics of the host membrane itself. The pristine poly(propylene) (PP) microporous membrane is inherently hydrophobic. However, the resulting composite membrane exhibits high water uptake, reaching up to 80%, when its pores are filled with a crosslinked poly(vinylbenzylammonium salt) hydrogel.25 As shown in the AFM image in Fig. 6, the hydrogel confined within the pores swells upon water absorption, thereby imparting a hydrophilic character to the otherwise hydrophobic PP membrane. It is noteworthy that the hydrophilic–hydrophobic balance in pore-filled membranes can be effectively tuned by incorporating hydrophobic groups, crosslinking agents, or spacer monomers.28,29 This is important for making a tailor-made membrane durable for a specific application.29 It is also important to note that the pore-filling, or the packing density of the hydrogel within the membrane pores, strongly influences water flux while maintaining desirable salt rejection during water softening.30 The extent of pore filling, and consequently the packing density, can be effectively controlled by adjusting the concentrations of the components in the pore-filling solution.
 | ||
| Fig. 6 AFM image of water-swollen crosslinked poly(vinylbenzyl ammonium chloride) filled in the pores of a poly(propylene) membrane by in situ crosslinking [reprinted from ref. 25, Copyright 2001, with permission from John Wiley & Sons]. | ||
It is expected that the diffusional transport properties, selectivity, and interfacial resistance (dielectric barrier) of a pore-filled membrane are largely governed by the guest hydrogel component, which occupies a major volume fraction of the membrane. Since the hydrogel is confined within the pores, the tortuosity factor, the ratio of the actual diffusion path length to the membrane thickness, is influenced by the pore architecture of the host membrane. Pore-filled membranes fabricated using a track-etched membrane (TEM) typically exhibit a tortuosity factor close to unity, as the straight cylindrical pores of TEMs provide direct diffusion paths.31 In contrast, other host membranes, shown in Fig. 4, possess interconnected or tortuous pores, leading to higher tortuosity and reduced diffusion efficiency. The confinement of the hydrogel within the pores also brings ion-exchange sites into closer proximity, thereby enhancing ion mobility and overall conductivity. For instance, the self-diffusion coefficients (D) of various counterions (Na+, Ag+, Cs+, Ba2+ and Eu3+) measured in three cation-exchange pore-filled membranes were found to be higher in those with a greater degree of mass gain.26 This behaviour can be attributed to the dense packing of ion-exchange sites in highly filled membranes, which facilitates faster ionic diffusion. The variation in D values follows the same trend as the ion-exchange capacities of the pore-filled membranes: PF3 (1.85 meq g−1) > PF1 (1.74 meq g−1) > PF2 (1.40 meq g−1).26 However, the range of D variation in the PF membranes is narrower than that observed for the Nafion-117 membrane. For example, in the PF-1 membrane, D varies from 0.79 × 10−6 cm2 s−1 (Na+) to 0.19 × 10−6 cm2 s−1 (Eu3+),26 whereas in Nafion-117, D varies from 1.03 × 10−6 cm2 s−1 (Na+) to 0.045 × 10−6 cm2 s−1 (Eu3+).32,33 This is attributed to the fact that the water uptake capacity of pore-filled membranes does not vary significantly, unlike Nafion membranes, whose water uptake is strongly influenced by the hydration characteristics of the counterions. Similarly, the specific conductivities (κ) of PF-1, PF-2, and Nafion-117 membranes were found to be 11.2 × 10−2 S cm−1, 13.0 × 10−2 S cm−1, and 7.4 × 10−2 S cm−1, respectively.26 This comparison clearly shows that the pore-filled membranes (PF-1 and PF-2) exhibit higher conductivities than Nafion-117 in their H+ ionic forms. This enhancement in conductivity can be attributed to the higher ion-exchange capacity and greater water content of the pore-filled membranes. The substantial water content facilitates proton mobility via the Grotthuss mechanism (proton hopping), thereby improving the overall transport performance of the membrane. The fast transport of H+via hopping water molecules is also responsible for the faster diffusional transport of HNO3 across the anion-exchange membrane.34 The pore-filled membrane, prepared by Lee et al. using an ultrathin substrate with a thickness of 16 μm, exhibited remarkably low ohmic resistance, leading to a reverse electrodialysis (RED) stack performance exceeding 1.3 times that of several commercially available membrane pairs.35 The reduced resistance can be attributed to the thin membrane architecture, its controlled swelling behavior, and the presence of a locally concentrated ion-conducting phase, all of these collectively promoted efficient ionic transport across the membrane. The interfacial thermodynamic resistance is a critical factor governing ion transfer from the aqueous phase to the membrane matrix, where the hydrophobic nature of the membrane can create a dielectric barrier.36 Since the hydrogel anchored in the pores of the membrane is hydrophilic and in direct contact with feed, it is expected that the interfacial thermodynamic resistance involved in the transfer of water/ions from feed to the membrane matrix would be minimum as compared to the membranes fabricated by using pure polymers. Therefore, faster diffusional-transport rates of Cr(VI) were observed in the pore-filled anion-exchange membrane with respect to more hydrophobic membranes.37
Conventional ion-exchange membrane fabrication typically involves complex procedures, extensive use of organic solvents, and optional post-treatment with strong acids or bases. Wang et al. suggested pore-filling as a green and straightforward method for cation-exchange membrane fabrication via an in situ pore-filling polymerization process using water as the sole solvent.38 They observed that the resulting pore-filled cation-exchange membranes exhibited high ion-exchange capacity, moderate water uptake, excellent mechanical strength, low area resistance (1.3 Ω cm2), and a high limiting current density (181 mA cm2), resulting in superior desalination performance. The low fabrication cost and excellent long-term stability underscore the strong potential of pore-filled membranes for scalable and sustainable industrial applications. This advancement is particularly significant for sustainable wastewater management, enabling integrated treatment technologies and circular resource recovery through green fabrication processes.39 The advantages and limitations, to be addressed by an appropriate strategy, are illustrated in Fig. 7.
 | ||
| Fig. 7 The summary of important properties, advantages, and limitations of pore-filled membranes compared with conventional membranes. | ||
The immobilisation of ionic liquids (ILs) and deep eutectic solvents (DESs) in the pores of synthetic polymer membranes offers a stable, high-performance electrolyte interface for electrochemical devices, especially where osmotic pressure differences are negligible. These liquid-filled membranes are expected to have high ionic conductivity, electrochemical stability, and low volatility of ILs and DESs with the mechanical strength of the polymer matrix, preventing leakage and evaporation while maintaining efficient ion transport. This approach minimizes internal resistance and electro-osmotic instabilities, enabling predictable performance in applications such as supercapacitors, fuel cells, batteries, sensors, and electrolyzers. In addition to these, the properties of these liquid-filled membranes could be tuned through the selection of polymers and solvents to match specific device requirements. Hernández-Fernández concluded that IL viscosity critically influences membrane design, with vacuum immobilization suited for low-viscosity ILs and pressure-based methods preferred for high-viscosity ILs to ensure effective pore filling.42 However, low-viscosity organic solvents can be immobilized just by immersing a hydrophobic porous microfiltration membrane, and organic liquids enter the pores by capillary action. This method has been employed at the pilot scale for the separation of rare-earth elements using supported liquid membrane extraction, wherein di(2-ethylhexyl) phosphoric acid (10% v/v in kerosene) was immobilized within poly(propylene) microporous hollow fibres.40
López-Porfiri et al. investigated SLMs composed of a PVDF porous support and ILs, [C2min][MeSO4], [C4min][BF4], and [C4min][PF6], demonstrating their potential for CO2/CH4 separation with performance comparable to conventional polymeric membranes.43 They found that the [C2min][MeSO4]-SLM and [C4min][BF4]-SLM exhibited good transmembrane pressure resistance under dry conditions but showed reduced stability by 48% and 28%, respectively, in humid environments. In contrast, the hydrophobic [C4min][PF6]-SLM offered lower pressure resistance but maintained consistent stability regardless of gas humidity. Le Mong et al. developed pore-filled solid electrolytes (PFSEs) for lithium–sulfur batteries by incorporating poly(arylene ether sulfone) double-grafted with poly(ethylene glycol) (PAES-g-2PEG), an ionic liquid (IL), and ethylene carbonate (EC) into a porous PP/PE/PP substrate.44 The substrate provides mechanical strength, while the PAES-g-2PEG network facilitates high Li-ion conductivity (0.604 mS cm−1) through a percolated ion-conduction pathway, aided by the IL and EC, resulting in membranes with 200 MPa tensile strength, thermal stability above 150 °C, a Li+ transference number of 0.41, and a wide electrochemical window of 4.60 V. The PFSE-based lithium-sulfur cell exhibited excellent cycling stability, retaining 95% of its initial capacity after 200 cycles at 0.2 C and stable Li stripping/plating for over 500 hours. These studies demonstrate the applications of IL-SLMs in diverse fields.
DESs are green, chemically tuneable alternatives to ILs and inorganic acids,45 and could be promising materials for membrane technology.46 Some of the important features of DESs are biodegradability, biocompatibility, low toxicity, ease of preparation and tuning desired properties such as hydrophilicity–hydrophobicity, viscosity, conductivity or extractive properties. DESs are formed simply by mixing a hydrogen bond donor (HBD) and acceptor (HBA) under mild conditions involving heating or mechanochemical processes, making them ideal for polymeric membrane development. Unlike ILs, DESs require no further purification, and their structure is stabilized by hydrogen bonding, along with electrostatic and van der Waals interactions.47 The durability of SLMs is significantly influenced by the physicochemical properties of the DESs, such as viscosity, polarity, and thermal stability, as well as key process parameters, including operating temperature, pressure, and the composition of the feed solution.48 These factors collectively affect the membrane's stability, selectivity, and long-term performance during applications. DESs immobilized in porous synthetic polymer membranes have been studied for various applications, such as gas separation, water treatment, extraction, electrochemical devices, etc., as given in Table 1.49–53
| Application | DES-SLM | Objectives | Ref. |
|---|---|---|---|
| High-voltage supercapacitors | Poly(vinylidene fluoride-co-hexafluoropropylene) membranes filled with DES (methylsulfonylmethane, LiClO4, and H2O) | Non-flammable and flexible quasi-solid-state electrolytes (excellent ionic conductivity, energy density of 45.3 Wh kg−1, and remarkable stability over 10![[thin space (1/6-em)]](https://www.rsc.org/images/entities/char_2009.gif) 000 consecutive cycles) |
49 |
| Facilitated C2H4 transport | Silver-based deep eutectic solvent constructed from trifluoromethanesulfonate and acetamide immobilized in a microporous membrane | Separation of C2H4/C2H6, excellent permeability of C2H4 and without loss of selectivity | 50 |
| Ethylene/ethane separation | Cu+ in a series of DESs (choline chloride (ChCl)-glycerol, ChCl-ethylene glycol, 1-butyl-3-methylimidazolium chloride ([Bmim][Cl])-G, and [Bmim][Cl]-EG) immobilized in a microporous membrane | CuCl/ChCl-EG-based SLMs possessed good permeability, comparable permselectivity, and good long-term stability | 51 |
| CO2 capture | Thymol-coumarin DES with 20% 4-formyl-morpholine immobilized in a PVDF flat sheet membrane | Permeability of 161.0 Barrer and a selectivity of 49.9 for CO2/N2 separation | 52 |
| Hollow fibre-electromembrane extraction | Hydrophobic deep eutectic solvent immobilized in hollow fibres | The method was effectively applied to quantify β-blocker concentrations in real urine and plasma samples, achieving relative recoveries ranging from 90.6% to 108.6% | 53 |
 | ||
| Fig. 8 In situ crosslinking of poly(vinylbenzyl chloride) (PVBCl) with piperazine in the pores of a poly(propylene) microporous membrane. | ||
The representative preformed polymers and crosslinkers used for in situ crosslinking-based pore filling and the applications of these membranes are listed in Table 2.37,54–66 There are several possibilities for using combinations of crosslinkable preformed polymers and corresponding crosslinkers. The crosslinkable polymers under ambient conditions include poly(vinyl benzyl chloride), poly(4-vinyl pyridine), poly(ethyleneimine), poly(diallyldimethylammonium chloride), poly(glycidyl methacrylate), poly(allylamine), and copolymers of vinylpyridine or glycidyl methacrylate. The crosslinker could be a diamine (piperazine, DABCO, etc.), dialkylhalide (α,α′-dichloro-p-xylene, 1,4-dibromobutane, etc.), or diepoxy crosslinker (ethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, etc.). The in situ crosslinking route for pore-filling is independent of the chemical composition of the host membrane, and can be used for microporous membranes made up of poly(propylene), poly(ethylene), poly(ether sulfone), polycarbonate or even ceramic-based membranes. Son et al. used pore-filling of functionalized poly(phenylene oxide) by centrifugal force in a poly(ethylene) support to form a homogeneous pore-filled membrane.61 As can be seen from Table 2, this method has been used for both flat-sheet or hollow fibre membranes.
| Preformed polymer | Crosslinker | Functionalization | Membrane | Application | Ref. |
|---|---|---|---|---|---|
| Poly(vinylbenzyl chloride) | 1,4-Diazabicyclo[2.2.2] octane (DABCO), piperazine | Trimethylamine in a 1:1 mixture of water and methanol |
Flat sheet | Water softening | 54 |
| Poly(4-vinylpyridine) | α,α′-Dichloro-p-xylene | Benzyl bromide in DMF | Flat sheet, hollow fibres | Water softening | 54, 55 |
| Polyethyleneimine | None | Flat sheet | Water softening | 56 | |
| Poly(vinyl alcohol) | Glutaraldehyde | None | Flat sheet, hollow fibres | Cathodic microbial fuel cell application, dehumidification membrane | 57, 58 |
| Poly(vinylbenzyl chloride) | 1,4-Diazabicyclo[2.2.2]octane (DABCO) | Excess of DABCO followed by alkylation with α,α′-dibromo-p-xylene (DBX), with excess of tetraethylenepentamine (TEPA), followed by alkylation with α,α′-dibromo-p-xylene (DBX) | Flat sheet | Diffusion dialysis based separation of Cr(VI), dibutyl phosphate | 37, 59, 60 |
| Acylated poly(phenylene oxide) | N,N,N′N′-Tetramethyl-1,6-hexanediamine (TMHDA) | Poly(phenylene oxide) with a long side chain and quaternary ammonium group through Friedel–Crafts acylation reaction | Flat sheet | Anion exchange membrane fuel cell system | 61 |
| High sulfonated poly(aryl ether ketone) | — | Crystalline poly(ether ketone) (PEK) was used as the matrix, and highly sulfonated poly(aryl ether ketone) (SPAEK) as the filler to fabricate PEK@SPAEK-x membranes via pore-filling technology | Flat sheet, proton exchange membrane | Direct methanol fuel cell | 62 |
| Poly(vinyl alcohol) | Glutaraldehyde | Fabricated using track-etched polycarbonate as the porous substrate and poly(vinyl alcohol) as the filler, with PVA stabilized by glutaraldehyde (GA) cross-linking over 24 to 96 hours | Flat sheet, pore-filled polyelectrolyte membrane | Cathodic microbial fuel cell | 63 |
| Poly(arylene ether ketone) with imidazole | — | Catechol and polyethyleneimine (PEI) are co-deposited to hydrophilize the pore of hydrophobic PTFE | Flat sheet PTFE | Vanadium redox flow battery | 64 |
| Poly(vinyl alcohol) | Glutaraldehyde | Filled the pores of the HDPE substrate with hydrogels consisting of glycerine, polyvinyl alcohol (PVA), and glutaraldehyde (GA) | Hollow fibre | Dehumidification | 65 |
| Polyethyleneimine | — | A solvent-free membrane adsorber was prepared by polydopamine coating and polyethyleneimine grafting on a PVDF membrane, enabling selective laccase immobilization directly from crude broth | Flat sheet PVDF microfiltration membrane | Enzyme purification, immobilization and catalysis | 66 |
The requirement of the extent of pore-filling by in situ crosslinking in the microporous host is highly dependent on the intended applications. The low-density pore-filling of hydrogel is well-suited for water-softening applications.30 However, high-density packing is required for diffusion dialysis/facilitated transport-based applications.37,59,60 The simplest way to enhance the packing density of hydrogels in pores is to use multi-linker crosslinkers such as tetraethylenepentamine (TEPA) for PVBCl, followed by alkylation with α,α′-dibromo-p-xylene (DBX).59 This leads to the formation of highly crosslinked hydrogels and prevents leakage of salts as required in the diffusion dialysis-based process. The chemical illustration of the formation of a highly crosslinked hydrogel by in situ crosslinking of PVBCl and subsequent modifications is given in Fig. 9.
 | ||
| Fig. 9 Formation of a highly crosslinked hydrogel in the pores of a microporous membrane. | ||
I. Thermal initiator-induced polymerization filling. The initiator-induced free radical mechanism requires either heat or electromagnetic radiation of the appropriate wavelength to dissociate initiators to form free radicals. Heat initiators, such as benzoyl peroxide, require heating at 80 °C for in situ thermally induced free radical polymerization, and have been used for making pore-filled membranes.75 Similarly, thermally induced in situ polymerization of acrylamide with the cross-linker N,N′-methylene bisacrylamide in pores of microporous membranes was carried out using a thermally activated initiator AZAP (2,2′-azobis(2-methylpropionamidine)dihydrochloride) at 85 °C for 90 min in an oven.76 An alkaline stable and hydroxide ion conducting pore-filled anion exchange membrane for alkaline fuel cell applications was made using thermal initiator BPO induced polymerization of 4-vinylbenzyl chloride and divinylbenzene in a PE microporous membrane at 100 °C for 12 h.77 For the capacitive deionization process, a cation-exchange membrane has been developed using AIBN as a thermal initiator in the preparation of poly(ethylene) membranes filled with crosslinked sulfonated polystyrene at 70 °C for 10 h.78 There are several thermal initiators, such as alkoxyamine, azo derivatives, and (hydro)peroxides, which can be used to initiate the in situ free radical polymerization of acrylate-based monomers.79 The thermal initiator-induced in situ polymerization route for preparing various kinds of pore-filled membranes is very effective in developing high-efficiency membranes and greener methods as compared to conventional methods. However, as temperatures ranging from 70–100 °C are used in thermally induced free radical polymerization, the major issues associated with this route of pore filling are the possibility of monomer evaporation, undesirable changes induced by heat in the host microporous membrane matrix, inhomogeneous pore filling, and scale-up issues.
II. Photoinitiator-induced polymerization filling. The initiator-based photopolymerization is a better route as it can be carried out at room temperature and is scalable to commercial production for the production of homogeneous pore-filled membranes. The photoinitiator-based in situ polymerization in pores of the microporous host membrane was first started by Childs's group at McMaster University, and they have developed several pore-filled flat sheets and hollow fibre membranes for water softening, removal of acids, human plasma proteins, membrane-mediated synthesis of nanocrystalline ferrihydrite, etc.55,68,72,80–86 These pore-filled membranes were prepared by in situ polymerizing 4-vinaylpyridine, acrylamido-2-methyl-1-propanesulfonic acid, (3-acrylamidopropyl)trimethylammonium chloride, acrylamide, methacrylic acid, acrylic acid, etc., monomers with suitable crosslinkers (5–10 wt%) in polyolefin and PES microporous host membranes (60–80% porosity) and using UV-initiators such as benzoin ethyl ether, α,α′-dimethoxy-α′-phenyl acetophenone and Irgacure®2959 (Ciba) using 365 nm light. A glycopolymer-filled microporous polypropylene membrane for pervaporation dehydration was formed by in situ copolymerization of acrylic acid and D-gluconamidoethyl methacrylate using AIBN as a UV initiator.87 Light-controlled free radical in situ polymerization in the pores of the host membranes could be used for developing several desired pore-filled membranes.88
It was observed that anchoring of hydrogels using this route could achieve as high as >200 wt% mass-gain, leading to dense hydrogel filling.55,68,72,80–86 This extent of high hydrogel loading in pores could be attributed to the higher concentration of monomer and crosslinker in the pore-filling polymerizing solution and the higher porosity of the microporous host membrane (70–80%). Thus, this kind of pore-filled membrane has mechanical reinforcement by the host membrane to the guest component hydrogel formed by in situ polymerization. The cross-sections of the representative pristine PES and corresponding pore-filled membrane given in Fig. 10 illustrate the physical architecture of these membranes.89
 | ||
| Fig. 10 The cross-sectional FESEM images of the pristine host poly(ethersulfone) membrane (a) and UV-initiator-induced polymerized poly(bis[2-(methacryloyloxy)ethyl] phosphate) in pores of the same PES membrane (b). The host matrix is a light colour fibrous matrix, and a dark coloured solid matrix represents the grafted component [reprinted with permission from ref. 89. Copyright (2016) American Chemical Society]. | ||
The photopolymerization of monomers involves the photolysis of the UV-initiator molecules at the surface of pore-filled membranes exposed to UV light. This is attributed to the fact that light <400 nm is absorbed in transparent plastics and cannot be transmitted.90 As UV light does not penetrate deep into the matrix, the free radicals and growing chains diffuse inside the pores to form homogeneous hydrogels throughout the membrane matrix. However, if in situ polymerization is fast, the bulk of the hydrogels would be formed on the surface of the membrane exposed to UV light, as observed in the in situ polymerization of glycidyl methacrylate with ethylene glycol dimethacrylate in pores of the poly(propylene) membrane using UV initiator α,α′-dimethoxy-α-phenyl-acetophenone and exposing both sides to 365 nm light.91 As shown in Fig. 11, the surface of the membrane became non-porous and the interior became highly porous after in situ polymerization, which could be attributed to asymmetric in situ polymerization based pore-filling.
 | ||
| Fig. 11 FESEM images of the surface (a) and cross-section (b) of the pristine host membrane, and the surface (c) and cross-section (d) of the same membrane after in situ polymerization of glycidyl methacrylate [reproduced from ref. 91 with permission. Copyright (2025) The Royal Society of Chemistry]. | ||
Yang et al. developed roll-to-roll fabrication of pore-filled anion-exchange membranes by integrated photopolymerization processing as shown in Fig. 12.92 The automated processing involves six steps, such as pretreatment, impregnation, lamination, polymerization, delamination, and polishing at a line speed of 0.3 m min−1.92 The lamination with a PET film was used to cut off atmospheric oxygen, which inhibits the free radical polymerization. The monomer, crosslinker, photoinitiator and host membrane were (3-acrylamidopropyl)trimethylammonium chloride, piperazine diacrylamide, photoinitiator Darocur 4265 and a porous substrate with a tri-layer of poly(propylene)–poly(ethylene)–poly(propylene), respectively. The photopolymerization was carried out using 365 nm light. This work demonstrates the possibility of large-scale production of pore-filled membranes via the photopolymerization route.
 | ||
| Fig. 12 Roll-to-roll fabrication of a pore-filled membrane by photopolymerization [reproduced from ref. 92, Copyright 2025, with permission from Elsevier]. | ||
It is not necessary that the functionalized monomers have to be used for forming desirable functionalized pore-filled membranes. The pore-filling using precursor monomers such as vinylbenzyl chloride and glycidyl methacrylate is amenable to chemical modifications under ambient conditions.93,94 It is also possible to employ click chemistry, such as (i) the Diels–Alder reaction, (ii) thiol-ene, and (iii) Cu(I)-catalyzed azide–alkyne cycloaddition (CuAAC), for fabricating membranes with desirable functionality.95 A water-based aza-Michael reaction can also make pore-filled membranes with desired chemical functionality.96 It is also possible to directly modify the base membranes. For example, poly(sulfone) membranes can be subjected to chemical modifications like the chloromethylation reaction, lithiation reaction, sulfonation reaction, etc., for generating desirable chemical architectures.97 Nanoparticles could also be incorporated in the membrane's pores by sol–gel methods, self-reduction, or ion-exchange-based loading of precursor ions, followed by in situ reduction.98–101 The representative applications of the pore-filled membranes prepared by in situ polymerization are given in Table 3.87,102–116
| Membrane composition | Preparation details | Applications | Ref. |
|---|---|---|---|
| Anion-exchange membrane | Thermal polymerization of a chloromethyl-functionalized monomer within a porous polyethylene substrate, followed by post-polymerization amination using trimethylamine | Alkaline fuel cell | 102 |
| Anion-exchange membrane doped with a mixed solvent | Polymerizing a PEGDA-VBC (7:3) monomer mix with 2 wt% BPO in porous substrates at 80 °C for 3 h, followed by amination in 0.5 M TMA for 3 h |
Dye-sensitized solar cells | 103 |
| Anion-exchange membrane | In situ photopolymerizing an imidazolium-functionalized ionic liquid monomer and crosslinker within the pores of a porous polyethylene support | Non-aqueous redox flow batteries | 104 |
| Anion-exchange membrane | Pore-filling of a monomer mixture of styrene, vinylbenzyl chloride, and divinylbenzene and 2 wt% BPO as an initiator in a commercial porous battery separator film, followed by thermal polymerization at 80 °C for 3 h and subsequent amination with trimethylamine solution for 5 h | Non-aqueous redox flow batteries | 105 |
| Surface-modified anion-exchange membrane | Prepared using porous polyethylene as the substrate, with (vinylbenzyl)trimethyl ammonium chloride and styrene as monomers, trimethylolpropane triacrylate as the cross-linker, and diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide as the photoinitiator, followed by UV curing for 5 min and subsequent surface coating with varying PPy/rGO ratios | Energy harvesting via reverse electrodialysis | 106 |
| Complexing ultrafiltration membrane | UV grafting of ethylene glycol methacrylate phosphate along with crosslinker N,N′-methylenebis(acrylamide) in pores of a PES membrane using an AIBN photoinitiator | Capturing uranium for analytical application | 107 |
| Cation-exchange membranes | Styrene and glycidyl methacrylate were copolymerized using benzoyl peroxide as an initiator and a mixture of three cross-linking agents (DVB, EGDMA, and HDDMA) within the pores of a commercial separator film. The resulting pore-filled membrane was then functionalized with sodium iminodiacetate and chlorosulfuric acid to produce a cation-exchange membrane | Capacitive deionization | 108 |
| Anion-exchange membrane | Pore filling of porous polyethylene was achieved via UV polymerization using a monomer mixture of (3-acrylamidopropyl)trimethylammonium chloride and (vinylbenzyl)trimethylammonium chloride with crosslinkers 1,4-bis(acryloyl)piperazine and trimethylolpropane trimethacrylate, and 2-hydroxy-2-methylpropiophenone as the photoinitiator | Water electrolysis | 109 |
| Anion-exchange membrane | The polymerizing solution was prepared by dissolving the monomer (3-acrylamidopropyl)trimethylammonium chloride, (3-acryloxypropyl)trimethoxysilane, and UV initiator 2,2′-dimethoxy-2-phenylacetophenone in a solvent mixture, filled in a UV polymerized polypropylene membrane | Recovery of nitric acid | 110 |
| Pd NP embedded composite membrane | UV polymerization of GMA/EGMP to form a crosslinked poly(ethylenimine) and poly(ethyleneglycolmethacrylate phosphate) filled polypropylene membrane | Membrane catalyst for organic & redox reactions | 111 |
| Glycopolymer-filled membrane | UV-initiated in situ copolymerization of acrylic acid (AA) and D-gluconamidoethyl methacrylate (GAMA) in pores of a polypropylene membrane using an AIBN initiator | Pervaporation dehydration | 87 |
| Poly(N-vinyl imidazole) gel-filled membrane | UV-initiated polymerization of N-vinyl imidazole with N,N′-methylenebisacrylamide in ultraporous polysulfone | Molecular separation | 112 |
| Anion-exchange membrane | Positively charged poly(N-vinyl imidazole) gel-filled loose nanofiltration (NF) membranes were fabricated by asymmetric gel-filling onto an ultrafiltration (UF) support, using UV-initiated surface grafting polymerization followed by post-quaternization | Nanofiltration | 113 |
| Environment-responsive ultrafiltration membrane | A hydrogel was formed by soaking a PVDF membrane in an isopropanol solution containing N-vinyl-caprolactam, 1-vinyl-2-pyrrolidone, bisacrylamide, and AIBN, followed by sandwiching between cellophane sheets and thermal polymerization at 70 °C for 8 h | Protein bioseparation | 114 |
| Solvent-free fabrication of pore-filled cation-exchange membranes | Porous PTFE was pretreated with a surfactant in an aqueous solution to render it hydrophilic. A polymerization solution containing sodium 4-vinylbenzenesulfonate, N,N′-methylene bis(acrylamide), and 1 wt% of the photoinitiator 2-hydroxy-2-methylpropiophenone dissolved in deionized water was then introduced into the membrane pores. The filled membrane was subsequently photopolymerized under ultraviolet light irradiation at 365 nm | Electrodialysis desalination | 115 |
| Polyelectrolyte hydrogel-filled membrane with a sulfonic acid group | A strong polyelectrolyte hydrogel was grafted onto a polyethersulfone (PES) ultrafiltration membrane via UV-induced copolymerization of vinyl sulfonic acid (VSA) and N,N′-methylenebisacrylamide (MBAA). Increased cross-linking and VSA content enhanced salt and uncharged solute rejection due to higher membrane charge density and steric exclusion | Nanofiltration | 116 |
III. Ultrasonic wave-assisted in situ polymerization. Ultrasonic wave-assisted in situ polymerization is similar to thermal or photopolymerization methods of pore-filling by initiating polymer formation directly within the pores using ultrasonic energy. In this process, a microporous membrane is coated with an initiator, such as BPO, and immersed in polymerizing solution containing monomers and crosslinkers and subjected to ultrasonication. In another route, a microporous membrane is impregnated with a polymerizing solution containing monomers, cross-linkers, and an initiator, followed by ultrasonication. Ultrasonic irradiation induces acoustic cavitation, generating localized high temperature and pressure, accelerating polymerisation and improving monomer penetration into the pores.
Qi et al. developed antifouling poly(vinylidene fluoride) (PVDF) hollow fibre membranes with hydrophilic surfaces using ultrasonic wave-assisted graft polymerization.117 They cleaned PVDF membranes and first soaked them in benzoyl peroxide (BPO)–acetone solution for 5 h, and then dried them overnight at room temperature. Acrylic acid monomer solutions were prepared in a 1:1 ethanol–water mixture. The BPO-coated membranes were immersed in this solution, degassed with nitrogen for 30 minutes, and heated at 60 °C in an oil bath. Graft polymerization was then performed under ultrasonic irradiation at controlled time and power. A poly(propylene) composite hollow fibre membrane pore-filled with an acrylic hydrogel was successfully fabricated via in situ ultrasonic wave-assisted polymerization, which was also employed for the in situ copolymerization of styrene and maleic anhydride to impart antifouling properties.118,119 Poly(propylene) hollow fibre membranes with natural amino acid-based zwitterionic antifouling surfaces were successfully fabricated using the same ultrasonic wave-assisted polymerization method, followed by an epoxy ring-opening reaction.120
IV. Excimer laser for membrane engineering. Excimer lasers, short for “excited dimer” lasers, are pulsed ultraviolet (UV) lasers that operate at wavelengths typically in the range of 193–308 nm, such as ArF at 193 nm, KrF at 248 nm, and XeCl at 308 nm. These high-energy pulsed UV sources are widely utilised in material processing applications due to their ability to induce photochemical ablation with high spatial precision and minimal thermal damage.121 In membrane engineering, pulsed excimer lasers have emerged as effective tools for surface patterning, controlled pore formation, surface modifications and pore-filling.122–125 One of the key applications of excimer lasers in membrane science is the precise fabrication of micro- and nanopores on polymer films. By adjusting laser parameters such as the pulse fluence, repetition rate, and beam profile, it is possible to produce uniform pores with a controlled size and geometry. Sancaktar's group has developed several responsive membranes by polymerizing the hydrogel in the pores formed by 248 nm KrF excimer laser ablation of a masked polymer film, followed by UV initiator-induced in situ polymerization in the thus-formed pores using the same excimer laser, which is analogous to the photopolymerization mechanism discussed earlier.126 The brief descriptions of different responsive membranes formed by this route are given in Table 4.127–131
| Membrane | Polymer film | Polymerizing solution | Application | Ref. |
|---|---|---|---|---|
| pH-responsive membrane | Polyimide (Kapton), a lithographic technique used for membrane fabrication | Grafting solution was prepared in distilled water using a monomer (acrylic acid), a crosslinker (N,N′-methylene bisacrylamide), and an initiator (Irgacure 2959) | Optimization of pulsed laser polymerization | 127 |
| Thermally responsive membrane | PET film covered by a stainless-steel mesh | N-Isopropylacrylamide, N,N′-methylenebisacrylamide, Irgacure 2959 | Pore-filled membranes exhibit excellent mechanical integrity and can reliably withstand pressures up to 0.31 MPa (45 psi). Their temperature responsiveness and controlled transport behavior were demonstrated across the lower critical solution temperature | 128, 129 |
| pH-responsive smart gating membranes | Polyimide, lithography technique to produce pores | Acrylic acid, and the same pulsed laser polymerization | The fabrication method developed is fast, efficient, solvent-free, and economical | 130 |
| Glucose-responsive membrane | Polyimide, lithography technique to produce pores | Acrylic acid was polymerized using the same pulsed laser polymerization method. Subsequently, the enzyme glucose oxidase (GOD) was immobilized onto the membrane via a carbodiimide-mediated amidation reaction. The immobilized GOD converted glucose into gluconic acid | The membrane exhibits an approximately linear drug release profile, with the release rate correlating directly to the ambient glucose concentration | 131 |
Radiation grafting methods can be broadly classified based on the mode of grafting, the location of functionalization, the underlying reaction mechanism, and the solvent environment used during grafting, as illustrated in Fig. 13.133–136 Based on the grafting protocol, the radiation grafting is typically conducted using either a simultaneous method or a pre-irradiation method. In the simultaneous or direct irradiation method, the polymer and monomer are irradiated together in solution, leading to in situ formation of radicals and immediate grafting. This approach is simple and leads to high grafting efficiency, but has the problem of homopolymerization. A small amount of an inhibitor, such as Fe2+ or Cu2+, is typically added to the solution to suppress unwanted homopolymerization reactions, which are likely initiated simultaneously with the desired graft copolymerization.136 Using low absorbed doses and dose rates is preferred, as it helps prevent mutual recombination, thereby avoiding the deactivation of primary radicals generated within the polymer matrix. Also, low doses can minimize scission of polymer chains in the host matrix. In another route of the direct method, the polymerizing solution containing monomers and crosslinkers is filled in the pores of microporous polymer membranes, and exposed to gamma rays or electron beams for free radical polymerization. The crosslinker in polymerizing solutions ensures that the homopolymer formed is also linked with grafted polymer chains, leading to hydrogels with a dense network of polymer chains. In the second pre-irradiation method, the irradiation atmosphere influences the grafting mechanism. The polymer is first irradiated, in air, inert gas, or vacuum, to form the free radicals and then exposed to a monomer, often diluted or emulsified. Elevated temperatures are preferred. Irradiation in air generates peroxides and hydroperoxides (peroxidation), while inert or vacuum conditions produce trapped free radicals within the polymer matrix. This method provides excellent control and avoids unwanted homopolymer formation but requires careful handling under oxygen-free conditions. The choice of radiation-induced grafting method depends on the reactivity of the monomer and the polymer matrix. Simultaneous irradiation is suitable for grafting less reactive monomers (vinyl monomers) onto radiation-sensitive polymers (PTFE), especially when high grafting levels are needed. Pre-irradiation and peroxidation are more effective for reactive monomers (acrylate-based monomers). Optimizing parameters like the monomer concentration, irradiation dose and rate, temperature, film thickness, and solvent type is essential for controlling graft depth and achieving uniform membrane composition. From a mechanistic point of view, most radiation grafting processes proceed via free radical polymerization, in which radiation-induced radicals on the polymer backbone initiate chain-growth polymerization of vinyl-type monomers. However, there may be different mechanisms operating depending upon the solvent–monomer–polymer chain combinations, as shown in Fig. 13.
 | ||
| Fig. 13 Overview of radiation-induced formation and grafting of hydrogels on polymer host supports. | ||
Radiation grafting can also be classified based on the grafting location, which strongly influences the desired application of the membrane. In surface grafting, monomers are primarily grafted onto the outer or near-surface regions of the polymer, enhancing interfacial properties like hydrophilicity, biocompatibility, and fouling resistance, which is of immense importance for filtration membranes and biomedical devices. The pore-filled membranes are formed by radiation grafting inside the pores, and these membranes are commonly used for ion-exchange membranes, proton exchange membranes, and battery separators. In some applications, both surface and pore-grafting may be required.
Controlled-radiation graft copolymerization is an advanced radiation-grafting technique that integrates principles of controlled/living radical polymerization.137 It is classified into three types based on reversible radical deactivation mechanisms: atom transfer radical polymerization (ATRP), reversible addition–fragmentation chain transfer (RAFT) polymerization, and nitroxide-mediated polymerization (NMP). In ATRP-mediated radiation grafting, a two-step process is used. In the first step, halogen-containing vinyl monomers (chlorinated or brominated styrene or methyl acrylate) are grafted onto a substrate via conventional radiation methods. In the next step, controlled grafting proceeds through a dynamic equilibrium between active propagating radicals and dormant species (typically alkyl halides). This ensures better control over the graft architecture, density, and chain length. NMP-mediated radiation graft copolymerization uses nitroxide compounds such as TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) to reversibly trap polymer radicals generated by ionizing radiation, enabling controlled “living” polymerization of vinyl monomers. Although this method offers precise control over the graft architecture, it typically exhibits a lower grafting rate compared to conventional techniques. RAFT-mediated radiation grafting involves chain transfer agents like dithiobenzoates or dithiocarbamates that form reversible dormant intermediates with propagating radicals, suppressing irreversible termination and allowing controlled growth. RAFT enables grafting of a wide range of monomers, including styrene, methyl acrylate, butyl acrylate, MMA, maleic anhydride, and acrylic acid, under mild conditions. Radiation-induced RAFT grafting has been successfully applied to various substrates such as polypropylene, PVDF, and cellulose. The representative applications of radiation-grafted membranes are summarized in Table 5.138–146
| Application | Radiation grafting method | Performance | Ref. |
|---|---|---|---|
| Phase-transfer catalytic porous membrane for nucleophilic substitution reactions | Hollow fibre PE membranes, immersed in 4-vinylpyridine/n-heptane solution, were irradiated by γ-rays under a N2 atmosphere | The radiation-grafted membrane exhibits good phase transfer catalytic activity in the nucleophilic substitution reaction involving n-bromooctane and KI | 138 |
| Anion exchange membranes for anion exchange membrane fuel cells | HDPE films and LDPE films were subjected to 100 kGy absorbed dose in air (peroxidation method) using a 4.5 MeV dynamic continuous electron-beam unit. Subsequently, irradiated films were grafted with vinylbenzyl chloride, followed by amination with trimethylamine | The HDPE-based AEM led to enhanced performance characteristics when the AEM was tested in a single-cell anion-exchange membrane fuel cell | 139 |
| Proton-exchange membrane for water electrolysis cells | Styrene, acrylonitrile, and 1,3-diisopropenylbenzene monomers were co-grafted into a preirradiated 50 μm ethylene tetrafluoroethylene base film, followed by sulfonation to introduce proton exchange sites | Radiation-grafted membranes exhibited properties superior to Nafion membranes and good performance in a water electrolysis cell | 140 |
| Anion-exchange membrane for fuel cells | The gamma radiation-induced grafting of vinyl benzyl chloride onto poly(vinylidene fluoride) was optimized to synthesize PVDF-g-VBC. The resulting grafted PVDF powders were then used to fabricate dual-fibre electrospun mats by combining inert PVDF with the commercial ionomer Fumion-FAA-3. The hot pressed fibres were reacted with trimethylamine to form an AEM | Ionic conductivity of 4.67 mS cm−1 at 25 °C, high ion exchange capacity of 1.35 mmol g−1 with a Young's modulus of 761 MPa | 141 |
| Separators for lithium-ion batteries | A porous polyolefin separator was functionalized via γ-ray co-irradiation grafting, where high-energy γ-rays generated active sites for polymerizing 4,4,5,5-tetramethyl-2-vinyl-1,3,2-dioxaborolane, an electron-deficient borane monomer. This process modified both the surface and pores, enhancing ion conduction throughout the separator | The electron-deficient B atom enhances lithium-ion conduction, increasing the transference number to 0.5 and improving cycle stability and capacity retention at high current rates in the half-cell | 142 |
| Anion exchange membranes for vanadium redox flow batteries | Grafting 1-vinyl-3-ethyl imidazolium tetrafluoroborate ([VEIm][BF4]) onto polyvinylidene fluoride (PVDF-g-IL) and casting it to a membrane | The cell assembled with the membrane exhibited a high coulombic efficiency of 98.64%, excellent capacity retention, and stable cycling performance at a current density of 100 mA cm−2, highlighting the potential of PVDF-g-IL-based AEMs for VRFB applications | 143 |
| Anion-exchange membrane for fuel cells | Electron beam grafting of vinylbenzyl chloride onto 25 μm thick poly(ethylene-co-tetrafluoroethylene) films using the peroxidation method, followed by amination with trimethylamine | A RG-AEM (IEC = 2.0 mmol g−1), synthesized via a greener protocol using a 30 kGy electron-beam dose, achieved a peak H2/O2 AEMFC power density of 1.16 W cm−2 at 60 °C, surpassing the 0.91 W cm−2 of the reference membrane (IEC = 1.8 mmol g−1) made by an earlier protocol | 144 |
| Dye wastewater treatment | Horseradish peroxidase (HRP) was immobilized onto epoxy-functionalized polypropylene (PP) films, which were prepared by grafting 2,3-epoxypropyl methacrylate (EPMA) onto microporous PP substrates via60Co gamma radiation-induced mutual graft polymerization | The immobilized enzyme system achieved approximately 90% degradation of brilliant red 29 over 20 days and demonstrated reusability for up to five cycles without significant loss of catalytic activity | 145 |
| Hydrophobic to hydrophilic membrane | Hydrophilic hydroxyethyl acrylate grafting on a hydrophobic polyvinylidene fluoride membrane by gamma grafting using the pre-irradiation method | The pH-sensitive PVDF membrane could be potentially useful for various applications | 146 |
I. Self-healing membranes. Hydrogels exhibit remarkable self-healing properties due to dynamic and reversible bonding, such as hydrogen bonding, ionic bonding, hydrophobic interactions, and π–π stacking.147–149 Therefore, hydrogel pore-filled membranes are also expected to have self-healing properties based on the chemical architecture of the hydrogel anchored in porous membranes. Membranes with self-healing capabilities can autonomously restore their original rejection performance, eliminating the need for expensive integrity monitoring and frequent membrane replacement. Getachew et al. developed hydrogel pore-filled membranes via in situ graft polymerization of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) onto microporous poly(ether sulfone) (PES) substrates, effectively demonstrating their self-healing behavior.150,151 They observed that the membranes were able to autonomously recover particle rejection levels up to 99%, even after dropping to as low as 30% due to physical damage. This self-healing capability was attributed to the swelling of the pore-filling hydrogel into the damaged regions, and strengthened with polymer chain inter-diffusion and hydrogen bonding. In addition to hydrogen bonding, ionic crosslinking by multivalent ions is also found to enhance the self-healing properties of the poly(AMPS)-hydrogel filled membrane, as shown in Fig. 14.152 A self-healing poly(ethersulfone) ultrafiltration membrane was developed using host–guest chemistry between cucurbit[8]uril (CB[8], a macrocyclic molecule with 8 glycoluril units) and two guest molecules.153 The membrane was fabricated using the reverse thermally induced phase separation (RTIPS) method and showed excellent self-healing ability, improved mechanical strength, high water flux, and strong BSA rejection. The self-healing behaviour was attributed to the swelling of the CB[8]-based hydrogel into damaged areas, molecular interdiffusion of hydrogel chains, strong hydrogen bonding, and host–guest interactions between CB[8] and the guest molecules.
 | ||
| Fig. 14 Self-healing mechanism of the poly(AMPS) hydrogel-filled membrane by dynamic and reversible H-bonding and ionic crosslinking. | ||
II. Electrically conducting membranes. Electrically conducting pore-filled membranes are fabricated by the in situ formation of poly(acetylene) (PA), poly(aniline) (PANI), poly(pyrrole) (PPy), poly(thiophene) (PTH), poly(para-phenylene), poly(phenylenevinylene) (PPV), and polyfuran (PF) in the pores of microporous membranes.154 A conjugated carbon chain, characterized by alternating single and double bonds, possesses highly delocalized and electron-rich π bonds that contribute to its unique electrical and optical properties.155 The electrical conductivity of such chains can be significantly enhanced through doping, which introduces charge carriers by either donating or accepting electrons. The in situ polymerization methods for anchoring the conducting polymers could be chemical oxidation, electrochemical polymerisation, vapor phase synthesis, hydrothermal, solvothermal, and photochemical methods, solid state methods, plasma polymerization, etc. The conducting polymer membranes find several applications as photocatalytic, electro-catalytic, and biocatalytic membranes.156 The representative applications of the pore-filled conducting membranes are listed in Table 6.157–162
| Application | Fabrication method | Major outcome | Ref. |
|---|---|---|---|
| Conductive nanofiltration membranes | Simultaneous interfacial polymerization and in situ HCl catalysed 3,4-ethylenedioxythiophene self-polymerisation to produce conductive poly(3,4-ethylenedioxythiophene)-doped nanofiltration membranes | Electro-assisted membrane fouling mitigation incurs only a marginal electricity cost of 0.055 $ per day | 157 |
| Conducting membranes | Conducting polymers were formed in situ on polyethylene membranes either through the oxidative polymerization of pyrrole from the gas phase or by polymerizing aniline hydrochloride induced by ammonium peroxydisulfate in an aqueous medium | Composite membranes have a low resistance in electrolyte solutions | 158 |
| Amperometric biosensor applications | In situ polymerization of 3,4-ethylenedioxythiophene by ferric chloride in pores of a track-etched membrane. The sensor was constructed with PEDOT + PVMP in the track-etched membrane to immobilize glucose oxidase | Stable sensor for glucose with enhanced sensitivity | 159 |
| Oil–water separation | A super-hydrophilic PANI/Ag/TA@PVDF composite membrane featuring a PANI–Ag nanoparticle heterojunction structure was fabricated via the chelation and reduction of Ag+ by tannic acid (TA), followed by the in situ growth of hydrochloric acid-doped polyaniline | Separation efficiency of more than 97% for soybean oil, and photocatalytic degradation ability | 160 |
| Polypyrrole membrane for antifouling and selective separation | A polypyrrole-dodecylbenzene sulfonate (PPy-DBS) membrane with tuneable pores is developed for selective separation and fouling control | Applying a redox potential alters the membrane's pore size via ion-driven volume changes. Under oxidation, pores expand to release foulants during backwashing, and then return to their original size under reduction | 161 |
| Vanadium flow battery | Porous PES membranes are modified via in situ polymerization of pyrrole using VO2+ as an oxidant. The resulting positively charged PPY nanoparticles enable vanadium ion retention through Donnan exclusion and enhance ion conductivity via interaction with sulfuric acid. The PPY/PES membranes thus exhibit high ion selectivity, conductivity, and chemical stability under VFB conditions | PPY/PES porous membranes showed promising performance in vanadium flow batteries (VFBs), with a coulombic efficiency of 96.30% and an energy efficiency of 87.20% at 80 mA cm−2, surpassing Nafion-115. They also maintained stable efficiency over 100 cycles, highlighting their potential for VFB applications | 162 |
III. Stimuli-responsive membranes. Hydrogels possess unique properties that enable them to undergo repeated swelling and deswelling without structural damage, exhibiting remarkable memory and reversibility. This behavior underlies their responsiveness to external stimuli.163 Swelling/deswelling transitions occur in two forms: continuous and discontinuous. In continuous transitions, the solvent gradually diffuses into the polymer network, driven by polymer–solvent interactions, allowing chain relaxation and expansion until equilibrium. Discontinuous transitions, in contrast, are triggered by subtle changes in molecular interactions, such as van der Waals forces, hydrophobic effects, hydrogen bonding, or bonding interactions, causing rapid shifts between swollen and collapsed states. These mechanisms allow hydrogels to respond dynamically to external stimuli, such as pH, temperature, ionic strength, electric field, magnetic field, light, chemical triggers, enzyme concentration, redox species, reactive oxygen species (ROS), and glucose levels.164 These stimuli-responsive hydrogels find applications in tissue engineering, sensors, controlled drug delivery, smart gating, microfluidics, food science and separation science.165–168 As hydrogels lack desirable mechanical properties, the pore-filling of these soft hydrogels in the microporous membranes could provide desirable functionality of the soft gels along with mechanical strength provided by the host membranes.23 The responsive hydrogels can be easily anchored in the pores of microporous host membranes as discussed above. A review by Huang et al. highlights various strategies for the preparation of stimuli-responsive membranes, including blending, casting, polymerization, self-assembly, and electrospinning, as well as their smart applications in separation processes.169 The stimuli-responsive pore-filled membranes used in different representative applications are listed in Table 7.170–178
| Responsive hydrogel | Host membrane | Pore-filling method | Stimuli | Application | Ref. |
|---|---|---|---|---|---|
| Poly(N,N-diethyl-2-acrylamide) | PVDF ultrafiltration membrane | Self-polymerisation/RAFT | Temp. (low critical solution temp. (LCST) of PDEA is 32 °C) | Imprinted composite membranes for the separation of ReO4− | 170 |
| Poly(N-isopropylacrylamide-co-acryloylamidobenzo-15-crown-5) | Porous nylon-6 membranes | Plasma-induced pore-filling grafting polymerization and chemical modification | K+-responsive gating action | Controlled release, chemical/biomedical separation, tissue engineering, sensors | 171 |
| Poly(methacrylic acid) and crosslinked poly(N,N-dimethylaminoethyl methacrylate) | PVDF | Plasma-graft pore-filling polymerization | pH-responsive gating | pH-responsive controlled-release systems | 172 |
| Poly(N-isopropylacrylamide) | Polyethylene terephthalate (PET) track-etched membrane | Photopolymerization | Temperature-responsive | Size-selective ultrafiltration/microfiltration | 173 |
| Poly (4-vinylpyridine) | PET track-etched membrane | Thermal/RAFT polymerization | pH-responsive | Separation of water–oil emulsions | 174 |
| Poly(N,N-diethylaminoethyl methacrylate) | PVDF | Polydopamine coating, followed by a thiol-terminated PDEAEMA reaction through Michael addition | CO2-responsive | CO2-controlled switching between the pore-open and pore-closed state | 175 |
| Azobenzene groups on SiO2 | Polypropylene membrane | SiO2 NPs were anchored in a PAA-grafted PP membrane, followed by chemical grafting of photosensitive 7-[(trifluoromethoxyphenylazo)phenoxy]pentanoic acid | Light responsive | Oil/water separation | 176 |
| Spiro-compounds | Track-etched polycarbonate membrane | Copolymerization of spiropyran was not only planned with methacrylates but also with acrylates after plasma activation | Light responsive | Controlled caffeine delivery | 177 |
| Magnetic nanoparticle embedded poly(N-isopropylacrylamide) | Track-etched PET | UV initiator and redox initiator in situ polymerization of the monomer along with amphiphilic polymer-coated magnetic iron oxide nanoparticles | Magneto-responsive | Switchable molecular sieving | 178 |
3. Fibre-reinforced hydrogels
Hydrogel pore-filled membranes are well-suited for separation applications. However, many applications require hydrogels to be used as such, especially in applications where soft materials are required. Many biological hydrogels in animal tissues, such as muscles, heart valves, cartilage, and tendons, exhibit exceptional mechanical properties, including high toughness, strength, resilience, adhesion, and fatigue resistance, which is attributed to fibre reinforcement in the hydrogel. These attributes are essential for hydrogels used in diverse applications, from drug delivery, tissue engineering, and medical implants to sensors, actuators, soft robotics, and wearable electronics.179 Therefore, fibre-reinforced hydrogels are being developed to impart the desirable mechanical properties to the hydrogels.180 In general, fibre-reinforced hydrogels are structurally advanced composite materials that combine a soft, hydrated polymer network with reinforcing fibrous elements to significantly improve their mechanical performance. These fibrous components, ranging from natural biopolymers like collagen or silk to synthetic fibres, such as poly(caprolactone) (PCL) and poly(vinyl alcohol) (PVA), and inorganic fibres (carbon or glass), act as a load-bearing framework within the hydrogel matrix. The reinforcement of fibres enhances tensile strength, toughness, elasticity, and fatigue resistance, addressing one of the major limitations of conventional hydrogels. The fibres may be randomly dispersed or directionally aligned, and their interaction with the hydrogel matrix is important to ensuring effective stress transfer and structural integrity. One of the most important applications of fibre-reinforced hydrogels is in tissue engineering, particularly for regenerating load-bearing soft tissues such as cartilage, tendon, ligament, and meniscus.181 These animal tissues exhibit a complex architecture in which collagen fibres are embedded within a hydrated proteoglycan-rich matrix, providing anisotropic and nonlinear mechanical behaviour.179 The tissue engineering requires specific properties, such as morphology, biochemistry, stiffness and physiology, depending on the type of tissue. The fibre-reinforced hydrogels are the most attractive scaffolds for tissue engineering, apart from controlled delivery platforms.182 The major biomedical applications of reinforced hydrogels are shown in Fig. 15. | ||
| Fig. 15 Healthcare applications of fibre-reinforced hydrogels. | ||
Electrospun nanofibers are emerging as a versatile technique to prepare reinforced hydrogels having desired mechanical strength, elasticity, and functionality suited for intended applications.183 Electrospinning produces nanofibers that mimic the fibrous structure of natural tissues and offer high surface area and tuneable porosity. In addition to this, the microstructure of the extracellular matrix of various tissues and the microenvironment of different cells could also be mimicked using this approach.184 Various methods for the integration of nanofibers in hydrogel matrices have been developed to form fibre-reinforced hydrogel composites. These are: (1) laminated hydrogels with electrospun nanofibers, (2) hydrogel precursors used as electrospinning solutions, (3) hydrogel components coaxially electrospun with other components, (4) electrospinning technology combined with 3D printing, (5) concurrent electrospinning/electrospraying technique, (6) electrospinning and photopatterning combination, etc.184 One of the simplest approaches is embedding electrospun fibre mats within or between hydrogel layers, creating a layered composite that resists stretching and tearing. Another method involves infusing hydrogel precursors into electrospun mats, followed by in situ crosslinking, which ensures strong interfacial bonding and a uniform structure. Alternatively, nanofibers can be electrospun directly into partially crosslinked hydrogels to form interpenetrating networks with enhanced flexibility and strength. The hydrogel can also be directly subjected to electrospinning to make electrospun hydrogel fibres for wound healing.185 The majority of reported fibre-reinforced hydrogels incorporate fibres produced via electrospinning, a technique that, while effective, offers limited spatial control over the fibre scaffold architecture. This constraint hampers the ability to conduct systematic mechanical testing and to tailor hydrogel properties through precise structural design. However, recent advances in manufacturing techniques, such as melt electro-writing and bioprinting, have significantly enhanced control over fibre deposition. These methods enable the fabrication of well-defined, customizable architectures, opening new avenues for investigating how specific structural features, such as fibre alignment, density, and interconnectivity, influence the mechanical performance and functional behaviour of fibre-reinforced hydrogels.186 The summary of different fibre-reinforced hydrogels developed recently is given in Table 8.187–194
| Hydrogel | Fibre | Methodology | Application | Ref. |
|---|---|---|---|---|
| Poly(vinyl alcohol)/gelatin hydrogel or with polyvinyl alcohol/gelatin + strontium–hardystonite composite hydrogel | Ultrahigh molecular weight polyethylene fibres | Fibres were impregnated with hydrogel | Biosynthetic tendon graft material | 187 |
| Methacryloyl gelatin/alginate hydrogel | Composite hydroxyapatite-coated poly(lactic acid) (PLA) fibre | 3D bioprinting technology | Tunable mechanical and osteogenic properties for bone repair | 188 |
| Gelatine-methacryloyl | PLA fibre | Melt-electrospinning writing | Tissue engineering | 189 |
| Poly(ethylene oxide) (PEO) hydrogels | Poly(ε-caprolactone) | PEO cross-linking was used to produce PCL fiber-reinforced PEO hydrogels from multilayer coextruded PEO/PCL composites | Tissue engineering scaffolds | 190 |
| Alginate hydrogel crosslinked with Ca2+ | Cellulose fibre | 3D-extrusion printers | Biocompatible single-use plastic tubing in the clinical setting | 191 |
| Crosslinked gelatin methacrylamide hydrogel | Poly(ε-caprolactone) | Melt-electrospinning in a direct writing mode | Tissue engineering | 192 |
| Gelatin | Natural protein zein | Coaxial electrospinning | Skin regeneration | 193 |
| Gelatin methacrylate | Poly (ε-caprolactone)-poly (ethylene glycol) microfibrous scaffold | Direct writing process | Regeneration of corneal stroma | 194 |
4. Engineering of soft materials on the surface and interface
Soft materials, such as polymers, hydrogels, elastomers, colloids, and biological macromolecules, exhibit a wide range of functional properties that make them ideal for advanced membranes, sensors, flexible electronics, and numerous biomedical applications. Engineering these materials at surfaces and interfaces is essential to unlocking their full potential, as interfaces are critical zones where mechanical, chemical, and biological interactions converge. Consequently, the design and control of interfacial properties play a pivotal role in determining the performance and functionality of soft material-based technologies, particularly both biological and artificial membranes.195 The surface and interface engineering of polymer membranes is gaining attention to address inherent issues of the membrane technologies, as illustrated in Fig. 16.196 | ||
| Fig. 16 Representative illustration of surface and interface engineering of soft materials on synthetic polymer membranes. | ||
There are several methods for the surface and interface engineering of synthetic polymer membranes, such as plasma treatment, surface grafting, interfacial polymerization, coating, molecular layer deposition, hot pressing of nanofibers, layer-by-layer assembly, mussel-inspired chemistry, etc., as shown in Fig. 17.197 The choice of the method is dependent on the desired functionality to be anchored on the membrane surfaces.
 | ||
| Fig. 17 Surface engineering of synthetic polymer membranes using different strategies. | ||
Membrane fouling is a major issue that deteriorates the performance, selectivity, and longevity of polymer-based separation membranes.198 Therefore, surface and interface engineering play a pivotal role in enhancing antifouling properties by tailoring interfacial interactions between the membrane and surrounding foulants. The major antifouling mechanisms, namely hydration, electrostatic repulsion, steric hindrance, and surface patterning, are typically achieved through precise modification of surface chemistry and the structure. Hydration is promoted by introducing hydrophilic functional groups or coatings, forming a stable water layer at the interface that acts as a physical and energetic barrier to foulant adhesion. Electrostatic repulsion is engineered by grafting charged moieties onto the membrane surface, thereby repelling similarly charged contaminants and preventing their accumulation on the surfaces to block the pores. Steric hindrance-based antifouling could be possible through the attachment of polymer brushes or bulky surface architectures that block foulant access via spatial obstruction. These interfacial strategies, rooted in the principles of surface engineering, are often used in combination to create multifunctional, fouling-resistant membranes capable of sustained performance in complex aqueous environments.198 Apart from antifouling, surface and interface engineering is also being extensively employed for selecting gating of molecules or ions, selectivity in solvent transport or imparting functionalities for catalysis (enzyme or photocatalysis), bio-compatibility and sensing mechanisms.
4.1. Importance of surface-engineered membranes
The selection of surface engineering methods for polymer membranes primarily depends on the chemical nature of the membrane material and the functional requirements of the intended application.199 In general, most polymers commonly used for membrane fabrication, such as poly(propylene) (PP) and poly(vinylidene fluoride) (PVDF), are chemically inert, making direct modification complicated. Among different inert synthetic polymer membranes, polypropylene membranes serve as a representative example. Wan et al. comprehensively reviewed surface engineering methods for microporous polypropylene membranes and their wide-ranging applications in membrane-based bioreactors, bioseparation, biosensing, biosynthesis, environmental analysis, water purification, energy systems, medical devices (such as artificial lungs and livers), and intelligent membrane separation processes.200 In contrast, other polymer membranes allow for specific chemical modifications owing to their functional groups. For example, poly(acrylonitrile) (PAN) contains nitrile groups that can be hydrolyzed to yield reactive carboxyl or amide groups, while aromatic polymers can undergo sulfonation to introduce sulfonic acid functionalities.201 These reactions broaden the scope of surface tailoring for diverse applications. Besides material chemistry, the intended application also governs the choice of surface engineering strategy. For instance, hydrophilization is often required for poly(propylene) membranes used in filtration processes to enhance water permeability and reduce fouling. Conversely, other applications may demand charged, hydrophobic, or biocompatible surfaces to achieve specific performance outcomes. Surface engineering plays a vital role in controlling interfacial properties, reducing fouling, tuning surface hydrophilicity/hydrophobicity, and selectively gating permeants at the membrane–feed interface. It is interesting to note that patterning of the surfaces of polymer membranes could also be employed for anti-fouling and reducing interfacial resistance.202However, the commercial-scale adoption of these technologies is often limited by techno-economic challenges, such as complex fabrication requirements, poor reproducibility, limited long-term stability, and difficulties in scaling up. Despite these challenges, the development of next-generation synthetic polymer membranes with tailored surface functionalities remains crucial for advancing sustainable and high-performance membrane-based separation technologies. One of the most successful applications of surface engineering is creating a superhydrophobic surface of a synthetic polymer membrane for oil–water separation.203 The important properties, advantages, and limitations of surface-engineered synthetic polymer membranes are summarized in Fig. 18.
 | ||
| Fig. 18 The graphical representation of important features of the surface engineering of synthetic polymer membranes. | ||
4.2. Surface patterning of polymer membrane surfaces
Surface patterning has emerged as a promising non-chemical strategy for enhancing the efficiency and durability of synthetic polymer membranes used in water purification, gas separation, and electrochemical systems.204 Patterned membranes exhibit superior antifouling and transport performance, primarily due to the combined influence of hydrodynamic and interaction effects introduced by surface topography modifications. The incorporation of well-defined surface features, ranging from the microscale to nanoscale, induces significant changes in local hydrodynamics, including increased shear stress, velocity gradients, and localized turbulence near the membrane–solution interface.202 These effects promote enhanced fluid mixing and reduce the thickness of the concentration boundary layer, thereby suppressing concentration polarization and mitigating foulant accumulation. Simultaneously, the topographical heterogeneity disrupts the hydrodynamic boundary layer, decreasing the effective contact area and adhesion forces between the foulants (bio or inorganic) and the membrane surface. Such modulation of membrane–foulant and foulant–foulant interactions contributes to improved fouling resistance and long-term operational stability. Besides hydrodynamic control, patterned surfaces influence interfacial mass transfer and surface energy distribution, leading to improved wettability and reduced foulant deposition. The presence of micro-eddies and secondary flow fields facilitates solute back-diffusion, maintaining a higher effective driving force for permeation. Consequently, membranes with patterned surfaces exhibit higher water flux, enhanced selectivity, and greater resistance to the flux decline compared to conventional flat membranes.205 The introduction of directional flow paths and increased effective surface area further promotes uniform permeation and selective solute transport. In pressure-driven processes such as ultrafiltration, nanofiltration, and reverse osmosis, these combined effects yield substantial improvements in both separation efficiency and operational lifespan.205 The fundamental antifouling mechanism can be attributed to enhanced fluid flow through turbulent eddies and back-vortices, which weaken foulant attachment and facilitate their detachment from the membrane surface. Thus, surface patterning offers a physical, energy-efficient means of fouling control without the use of chemical additives or surface coatings.For ion-exchange membranes (IEMs) employed in electrodialysis, fuel cells, and other electrochemical processes, surface patterning also reduces ionic resistance by improving ion transport pathways and mitigating concentration gradients.204 Enhanced mass transfer and reduced polarization lead to higher current density, improved power output, and overall better electrochemical performance.205 Surface patterning of ion-exchange membranes, particularly PEMs, offers significant potential to enhance fuel cell efficiency.205 It increases the membrane–catalyst interface area, enabling higher performance with lower catalyst loading and reduced resistance due to membrane thinning. These patterns shorten reactant pathways, improving mass transport and catalytic activity, thereby boosting current and power densities. Multiscale patterns combining nano- and microstructures further enhance surface area and performance, though their fabrication remains complex and costly, with optimal benefits achieved only when catalyst particles are smaller than the pattern dimensions. However, achieving such benefits requires a comprehensive understanding of the relationship between pattern geometries, feature dimensions, and fabrication methods, as these parameters collectively determine the resulting hydrodynamic and interfacial properties.206 It is important to note that the choice of patterning strategy depends on the desired feature scale, material compatibility, and intended application.
There are several techniques to produce patterns of macro-, micro-, and nano-scales on the surfaces of synthetic polymer membranes.205 The techniques employed for the surface patterning of the membranes can be categorized into template-based micro-moulding and direct printing.207 The example of template-based micro-moulding could be solution-based or embossing. The direct printing could be inkjet printing or 3D printing.205,207 Soft lithography enables transfer of micro- to nanoscale features using elastomeric stamps, offering simplicity and compatibility with polymers such as PVDF and PES, though large-area uniformity remains a challenge. Nanoimprint lithography provides superior pattern fidelity and resolution by embossing a hard mould onto a softened polymer surface, producing nanopillar or nanopore arrays that enhance selectivity and flux. Laser-induced patterning enables the direct, mask-free fabrication of periodic microtextures through localised ablation, thereby improving shear-induced foulant removal and wettability control.208 Laser-patterned porous membranes enable the fabrication of cost-effective, high-performance functional membranes suitable not only for CO2 separation but also for a wide range of applications, including water treatment, cell culture, micro-total analysis systems (micro-TASs), and membrane reactors.208 Macroporous hydrogel membranes can be fabricated using photolithography, which enables precise control over pore size, geometry, and spatial distribution within the polymer network.209 Such structured hydrogels provide high surface area and controlled microenvironments favorable for efficient enzyme immobilization and enhanced catalytic performance. Non-lithographic approaches such as phase separation-induced patterning exploit spontaneous structure formation during membrane casting, providing scalable roughness control for self-cleaning and high-permeability membranes.205 Template-assisted methods, utilizing colloidal or biological templates, and 3D printing enable hierarchical or customized architectures with spatially controlled functionality. Lithographic methods favor precision and tunability,210 while phase separation and laser-based approaches offer scalability for practical antifouling and selective separation membranes. The summary of different patterning techniques and their applications in water permeability membranes and ion-exchange membranes is illustrated in Fig. 19.
 | ||
| Fig. 19 Overview of surface patterning techniques employed to modify synthetic polymer membranes, and their effects on surface properties that enhance performance in filtration and ion-exchange membrane applications. | ||
4.3. Plasma-based treatment and grafting
One of the most employed techniques for surface modifications of synthetic polymer membranes is plasma-based treatment and grafting.196,211–213 In general, plasma treatment primarily modifies only the surface layers of the polymer without affecting the bulk properties, enabling precise control over interfacial characteristics.211 Plasma is an ionized gas generated by applying a strong electrical discharge in a low-pressure environment. When plasma interacts with the surface of synthetic polymer membranes, high-energy species induce electronically excited states in polymer chains, causing homolytic bond cleavage and the formation of surface-bound free radicals and unsaturated bonds.212 These reactive sites facilitate crosslinking within the polymer and act as a linker for graft polymerization or chemical bonding with external species introduced post-treatment, as shown in Fig. 20. For example, exposure to oxygen or water vapor following plasma treatment promotes the incorporation of oxygen-containing functional groups, thereby enhancing surface hydrophilicity. Plasma-induced surface modification (Ar and He) primarily generates surface radicals, which can subsequently react with other molecules introduced after plasma treatment. Reactive gases (O2, NH3, and CO2) contribute directly to the formation of functional groups during plasma exposure. For example, O2 plasma is commonly used to incorporate hydroxyl groups onto polymers like poly(caprolactone) (PCL), poly(ethylene) (PE), poly(ethylene terephthalate) (PET), and other polymers, creating biocompatible hydrophilic surfaces.214–219 Amine functionalities, which are particularly desirable for biomedical applications due to their biocompatibility and utility in covalent immobilization of biomolecules like enzymes, polysaccharides, and DNA, can be introduced using nitrogen-based plasma systems such as N2, NH3, Ar/NH3, and O2/NH3.220–222 The addition of inert gases like argon (Ar) to these reactive plasma systems enhances radical formation, promoting a higher density of nitrogen and oxygen functionalities. However, it has been reported that the Ar plasma treatment produces higher surface roughness as compared to N2 plasma on cellulose nitrate membranes.222 CO2 plasma treatment of polymers such as poly(propylene) (PP), poly(styrene) (PS), and PE generates carboxyl, ester, and ketone groups, although the diversity of functionalities can limit homogeneity for further modification.223,224 Despite their advantages, plasma-treated surfaces may undergo hydrophobic recovery over time due to reorientation of polymer chains to minimize surface energy. This effect, which reduces surface hydrophilicity, can be mitigated by storing the membranes in water immediately after treatment. | ||
| Fig. 20 Plasma-based methods for surface engineering of soft materials on synthetic polymer membranes. | ||
Plasma-induced grafting combines the generation of surface radicals via plasma treatment with the subsequent exposure to monomers, allowing for controlled polymerization at the surface.223 This is similar to radiation grafting discussed above, involving activation with plasma to form free radicals, followed by graft polymerization.211 The plasma activation involves the exposure of the polymer surface to RF-low-pressure plasma, using gases such as oxygen, argon, nitrogen, or air. This exposure creates free radicals on the surface of the polymer without affecting its bulk properties. These free radicals react with water and O2 molecules to form peroxides, or directly undergo graft-polymerization if the precursor monomer is present in the plasma itself. In the case of the absence of precursor monomers in plasma, the plasma-exposed surface of the polymer is brought into contact with a selected monomer in a subsequent solution or vapour phase step. The reactive sites on the surface initiate graft polymerization, leading to the formation of a thin, functional polymer layer that is chemically bonded to the underlying substrate. Plasma grafting, when combined with controlled/living radical polymerization techniques such as reversible addition-fragmentation chain transfer (RAFT) and atom transfer radical polymerization (ATRP), offers a powerful strategy for the precise modification of synthetic polymer surfaces.211,225,226 While plasma treatment alone can activate inert polymer surfaces by generating reactive species such as free radicals or peroxides, the integration of RAFT or ATRP enables controlled graft polymerization, allowing for the synthesis of polymer brushes with control over key parameters such as chain length, molecular uniformity, polymer architecture, and the functional properties of the grafted polymer brushes.
4.4. Mussel-inspired surface engineering
Mussel-inspired surface engineering, based on dopamine and its derivatives, provides a mild, multifunctional and highly adaptable platform for the surface modification of synthetic polymer membranes for water treatments to biomedical applications, as a modifier, adhesive layer, interfacial bridge, surface anchor, and initiator.227–229 This approach draws inspiration from the extraordinary underwater adhesion of marine mussels, which secrete foot proteins rich in 3,4-dihydroxyphenylalanine (DOPA). These proteins exhibit strong adhesive interactions with a wide variety of organic and inorganic surfaces, attributed to their catechol and amine functionalities. DOPA has multiple mechanisms to bind with organic and inorganic surfaces, resulting in durable, conformal, and chemically functional coatings across a broad range of substrates and environmental conditions. Mussel-inspired chemistry for the surface engineering of synthetic polymer membranes, along with possible adhesion mechanisms, is illustrated in Fig. 21. | ||
| Fig. 21 Illustration of mussel-inspired surface engineering of surfaces using representative dopamine as an example. | ||
Dopamine (DA), a molecule analogous to DOPA, functions as a bioinspired “molecular glue” and has been extensively adopted for membrane surface modification.230 When exposed to mildly alkaline aqueous environments, dopamine undergoes oxidative self-polymerization to form a uniform and strongly adherent poly(dopamine) (PDA) coating, which involves multiple intermediate reactions.231 Due to its insolubility, the precise structure and polymerization mechanism of PDA remain elusive. Typically, PDA is synthesized under alkaline conditions (pH ∼8.5), where the polymerization is believed to proceed via an equilibrium pathway, forming indole-like repeating units that result in a cross-linked network. Interestingly, PDA can also be synthesized under acidic conditions (pH ∼4.0) in the presence of an oxidant such as ammonium persulfate (APS), a pathway that cannot be fully explained by the conventional polymerization mechanisms.232 In general, the process of PDA coating is simple and substrate-independent, and proceeds under ambient conditions, making it highly suitable for modifying the soft surface of membranes. Compared to traditional methods like UV or plasma-induced grafting, PDA deposition is less damaging to the membrane structure and provides better control over surface chemistry. The resulting PDA layer plays multiple crucial roles in membrane engineering. It serves as a surface modifier, significantly enhancing the hydrophilicity, surface energy, and interfacial chemistry of otherwise hydrophobic membranes such as poly(vinylidene fluoride) (PVDF), poly(ethersulfone) (PES), poly(propylene) (PP), and poly(tetrafluoroethylene) (PTFE).187 These changes contribute to reduced fouling, improved water flux, and increased compatibility with further surface functionalization. The combination of poly(dopamine) (PDA) coating with a simple procedure and its excellent biocompatibility and versatile post-functionalization capabilities has led to rapidly growing interest across a wide range of applications, including energy storage, environmental remediation, cell encapsulation, and drug delivery.227–230,233
The adhesion mechanism of PDA to surfaces is multifaceted and includes covalent bonding, hydrogen bonding, π–π stacking, van der Waals interactions, and notably, metal–catechol coordination, as shown in Fig. 21.234 The catechol moieties can chelate multivalent metal ions such as Fe3+ or Ti4+, while the oxidized quinone groups engage in covalent reactions with nucleophiles like amines and thiols via Schiff base formation or Michael-type addition. This multifactorial adhesion strategy results in conformal and stable coatings even on low-surface-energy or chemically inert materials. In addition to its adhesive function, PDA could also be utilized as an intermediate layer that facilitates further chemical modification. It provides a chemically rich platform for the immobilization of functional entities such as poly(ethylene glycol) (PEG), zwitterionic polymers, enzymes, antimicrobial agents, etc. These modifications impart desirable functionalities on the surface of the membrane, such as anti-biofouling,234 catalytic activity, selective ion separation, or enhanced biocompatibility. The functional groups present on PDA can initiate secondary graft polymerization of monomers like acrylates, allowing the formation of surface-tethered polymer brushes, responsive hydrogels, or crosslinked nanocomposite layers.235 This property is especially valuable in constructing multifunctional or stimuli-responsive membrane interfaces. To mitigate biofouling, mussel-inspired molecular interaction strategies have emerged as effective approaches for designing anti-biofouling materials. These materials are engineered to either repel proteins and microorganisms, preventing their attachment, or to eliminate them actively in the surrounding environment.234 Surface-initiated free-radical polymerization of mussel-inspired dopamine, enabled by the immobilization of initiators on the substrate, allows for the fabrication of well-controlled hydrophilic coatings with tunable thickness and surface properties.236 The representative applications of using dopamine and its derivatives for the surface engineering of membranes are shown in Table 9.235,237–245
| Application | Details of surface engineering | Outcome | Ref. |
|---|---|---|---|
| Oil/water separation | A mussel-inspired dip-coating method was developed to form a stable hydrophilic polymer network on PVDF microfiltration membranes. Polydopamine treatment followed by catechol-functionalized hydrophilic polymer coating enabled the formation of a robust hydrophilic layer on the membrane surface | The introduction of a hydrophilic polymer network offered distinct advantages over other modification methods, particularly in enhancing separation efficiency | 235 |
| Membrane water-treatment performance | To enhance the long-term stability and performance of PVDF membranes for water treatment, a zwitterionic catechol-containing PEG modifier (SZ-PEG) was synthesized and blended with PVDF | The resulting PVDF/SZ-PEG membranes exhibited excellent fouling resistance and high porosity | 237 |
| Removing dyes from wastewater | The surface of the poly(phenylene sulfide) (PPS) membrane was modified via co-deposition of polyethyleneimine (PEI) and mussel-inspired PDA, where PEI was cross-linked with PDA through a chemical reaction | Higher anti-fouling properties, dye rejection, and resistance to organic solvents | 238 |
| Oil-in-water emulsion separation | Co-deposition of PDA and PEI on a polypropylene microfiltration membrane | Improved hydrophilicity | 239 |
| Wettability for harsh water treatment | Simultaneous polymerization of mussel-inspired dopamine and hydrolysis of commercially available and low-cost silane on a UF/MF membrane | Efficiently treating protein-rich water with significantly enhanced performance, and separating oil-in-water emulsions | 240 |
| Biomedical applications | Dopamine (DA) is grafted onto poly(sodium 4-vinylbenzenesulfonate)-co-poly(sodium methacrylate) (HepLP) or heparin via carbodiimide chemistry to form DA-g-HepLP and DA-g-Hep, respectively. These grafted polymers are then used to coat polyethersulfone (PES) dialysis membranes, creating heparin-mimicking surfaces | Remarkable blood and cell compatibilities | 241 |
| Lithium-ion battery separator | Cellulose microfibers were surface-modified with PDA coating, followed by the fabrication of a cellulose/PDA membrane through a papermaking technique | The separator exhibited improved cycling stability and rate capability compared with those of commercialized polypropylene separators and the pristine cellulose separator | 242 |
| Metal ion sorption | Coating PDA on nanofibrous mats fabricated with a blended solution of polyacrylonitrile and polysulfone in N,N′-dimethyl acetamide by electrospinning | New adsorbent material for pre-concentrate or separate La(III) in separation processes of hydrometallurgy | 243 |
| Wound hemostasis applications | Polycaprolactone (PCL) nanofiber membranes were fabricated via electrospinning, followed by the development of a PCL-PDA loading system through surface coating with PDA and loading of thrombin | High hemostatic performance and low preparation cost | 244 |
| Solar-driven membrane distillation | Coating of PDA on polyvinylidene fluoride to prepare photothermal membranes | Higher energy efficiency (45%) and the highest water flux (0.49 kg m−2 h−1) using a direct contact membrane distillation system under 0.75 kW m−2 solar irradiation | 245 |
Mussel-inspired hydrogels, known for their exceptional adhesive properties and biocompatibility, have been extensively explored across a wide range of applications.246 In biomedical engineering, they are utilized for tissue adhesives, wound healing dressings, and drug delivery systems due to their strong wet adhesion and bioactivity. In soft electronics and actuators, these hydrogels offer stretchability, conductivity, and self-healing capabilities, enabling the development of flexible and responsive devices. The ability of these hydrogels to conform to complex surfaces while maintaining functionality makes them ideal candidates for wearable sensors that monitor physiological signals in real time.
4.5. Other surface engineering techniques
Layer-by-layer (LBL) assembly is a simple and versatile technique for fabricating charged thin-film active layers by sequentially depositing oppositely charged polyelectrolytes on membranes. It has emerged as a promising method for developing high-performance separation membranes with enhanced permeability, selectivity, antifouling properties, chlorine resistance, and long-term stability.247 The LBL-assembly could be produced by a variety of methods, such as dip coating, spray coating, spin coating, inkjet printing, electric field, and high gravity techniques, for applications in nanofiltration, reverse osmosis, ultrafiltration, microfiltration, forward osmosis, pervaporation, and organic solvent nanofiltration.248 LBL-assembly has also generated significant attention due to its precise nanoscale control over film characteristics and broad material versatility for biomedical applications, with possibilities of tailored properties for uses ranging from surface modification to tissue engineering.249Molecular layer deposition (MLD) is a scalable technique for fabricating ultra-thin, smooth, and chemically uniform polymer films with nanometer precision. Similar to atomic layer deposition (ALD), MLD differs by incorporating organic linkages rather than individual atoms, enabling the creation of polymeric thin films. Both MLD and molecular layer-by-layer (mLBL) are layer-by-layer processes offering monomer-level control and conformal film growth.250 However, MLD provides more precise thickness control (∼0.4 nm per cycle) compared to mLBL (∼1 nm per cycle). While mLBL is simple and conducted at ambient temperatures, it involves long cycle times and high solvent use, limiting scalability. In contrast, gas-phase MLD is solvent-free, faster (sub-second cycle times), and compatible with roll-to-roll (R2R) manufacturing, making it more commercially viable. MLD has been explored for tuning membrane pore size, hydrophilicity, and antifouling properties.250 However, developing freestanding MLD films remains challenging due to their conformal, isotropic growth. MLD tends to deposit materials within pore structures rather than across them, posing technical barriers for desalination membrane fabrication. The active surface of a commercial NF270 membrane was modified by Chaudhury et al. using molecular layer deposition (MLD) of ethylene glycol-Al (EG-alucone).251 Initially, the precursors infiltrated and deposited within the active layer, then expanded it, and finally formed a distinct surface coating. This process altered the membrane morphology and reduced its fixed negative charge due to the incorporation of positively charged EG-alucone. Filtration tests showed that these changes affected ion separation, increasing Na+ permeability relative to Mg2+, without significantly impacting water flux. Welch et al. compared the structure, chemistry, and morphology of commercial interfacial polymerization (IP) membranes with lab-made molecular layer deposition (MLD) films.252 They observed that compared to IP films, MLD films were denser and more conformal, reducing voids and improving salt rejection.
5. Piezoelectric and nanofiber membranes
Piezoelectric polymers are a class of materials capable of converting mechanical stress into electrical signals and vice versa. Unlike brittle ceramic counterparts, these polymers are lightweight, flexible, and easy to process, making them particularly attractive for synthetic polymer membranes in biomedical applications.253 The most commonly used membrane material poly(vinylidene fluoride) (PVDF) and its copolymers exhibit notable piezoelectric responses due to their polar crystalline β phase, i.e., PVDF exhibits a higher piezoelectric coefficient (18 × 10−12 C/N).254 PVDF is a thermoplastic semicrystalline polymer whose common copolymers, poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE), poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE), and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), exhibit distinctive ferroelectric, pyroelectric, and piezoelectric properties depending on their phase structures.255–257 PVDF-CTFE allows efficient grafting via atom transfer radical polymerization (ATRP) without compromising thermal, mechanical, or chemical stability, resulting in improved membrane distillation (MD) performance.258 PVDF-TrFE predominantly exists in the β-phase, while PVDF-HFP provides higher mechanical strength, lower crystallinity, greater solubility, increased free volume, and improved hydrophobicity, making it widely used for separation membrane fabrication, including Li-ion battery separators.259–262 In membrane applications, piezoelectric polymers enable dynamic control over separation performance by coupling mechanical deformation with electrical polarization. When subjected to mechanical vibrations or pressure fluctuations, the generated electric field can influence ion transport, surface charge distribution, and fouling behaviour. Such membranes are being explored for self-cleaning filtration,263 flexible sensors,264 and nanogenerators,265 where mechanical energy from fluid flow or pressure variations is converted into electrical energy to enhance process efficiency or provide real-time monitoring. Piezoelectric PVDF membranes with self-powered and electrified antifouling capabilities have been developed for pressure-driven ultrafiltration processes, where the inherent piezoelectric properties of PVDF generate surface charges under mechanical stress, enabling active fouling mitigation without the need for external power sources.266 Several advanced piezoelectric PVDF membranes have been developed for advanced applications, such as PVDF-based piezo-catalytic membranes for treating textile wastewater,267 piezoelectric nanofiltration membranes with improved salt rejection,268 tissue engineering,269 energy transducers and membrane distillation,270 emulsion separation,271etc. PVDF and its copolymers, composites, and blends possess versatile characteristics, excellent processability, and tunable properties, enabling their implementation in diverse fields such as sensors, actuators, energy harvesting and storage devices, environmental membranes, microfluidics, tissue engineering, and antimicrobial applications.257From a design perspective, electrospun nanofibers have the potential to meet the requirements of diverse applications of synthetic polymer membranes, including PVDF piezoelectric membranes. Xue et al. reviewed methods, materials, and diverse applications of electrospinning and electrospun nanofibres.272 It is seen from this review that integration of electrospun nanofibers with membranes exhibits additional functionality, which would be significant for a given application. Mokhtari et al. reviewed applications of electrospun PVDF-nanofibers for energy and environmental applications.273 Electrospinning of piezoelectric PVDF-nanofibers would result in desirable molecular orientation, crystalline phase development, fibre morphology, and ultimately the piezoelectric performance of the material in intended applications. Polymer nanofibers, with or without additives, exhibit outstanding antifouling properties regardless of their base polymer composition. One of the most desirable applications of electrospun nanofibres anchored on the surfaces of synthetic polymer membranes is the mitigation of fouling and enhancing separation characteristics.274 Electrospun nanofiber membranes have been successfully applied across various separation processes, including microfiltration (MF), reverse osmosis (RO), forward osmosis (FO), membrane distillation (MD), heavy metal removal, and oil–water separation.275 Their high porosity, interconnected pore structure, large surface area, and tunable morphology offer superior permeability, selectivity, and antifouling performance compared to conventional membranes.276 The electrospun nanofiber membranes have also found significant applications in tissue engineering, wound dressings, cancer diagnosis and therapy, and medical protective equipment, owing to their high surface area, tuneable porosity, and excellent biocompatibility, as can be seen from a recent review.277
Metal–organic frameworks (MOFs) as additives in electrospun nanofibres have potential for developing advanced materials for energy storage and environmental applications, while addressing issues normally encountered by standalone MOFs in practical applications.278 MOF–nanofibre composites are typically prepared either by in situ growth of MOFs on fibre surfaces or by incorporating pre-synthesized MOFs into nanofibres, and could be used for selective removal of heavy metal ions.279 Electrospun MOF–nanofiber membranes have been found to be effective in photocatalysis, i.e. degradation of organic pollutants.280 Electrospun PVC membranes embedded with post-metalated MOFs (UiO-66(COOH)2-Ag and ZIF-8-Ag) show high structural integrity and functional performance,281 while oriented MOF/SPPESK nanofibre membranes demonstrate superior proton conductivity (8.2 × 10−2 S cm−1 at 160 °C), oxidative stability, and methanol resistance, achieving permeability as low as 6% of Nafion-115.282 MXenes are another class of advanced functional materials whose standalone applications pose several challenges. However, similar to MOFs, MXene functionalized electrospun nanofibers could address these challenges and find extensive applications in biomedical engineering,283,284 piezoelectric sensors,285,286 and energy materials.287,288 Therefore, electrospinning nanofibers embedded with advanced materials, often difficult to utilize independently, offer a promising route to fabricate high-performance membranes tailored for specific applications in the environment, healthcare and energy.
Hybrid membranes formed by integrating polymer nanofibers with ultrafiltration membranes combine the functional versatility of nanofibers with the mechanical strength and stability of the base membrane. This integration imparts desirable properties such as enhanced selectivity, permeability, and antifouling performance to otherwise inert membranes. Dobosz et al. enhanced ultrafiltration membranes's performance by integrating a 50 μm thick electrospun nanofiber layer of cellulose or poly(sulfone), composed of randomly accumulated 1 μm fibers.289 They observed that a high-porosity nanofiber layer improved fouling resistance and maintained selectivity without altering the base membrane structure. Poly(sulfone) nanofiber membranes exhibited higher pure-water permeance over a wider pressure range due to better mechanical integrity, demonstrating the potential of nanofiber-enhanced membranes as versatile platforms for improving ultrafiltration performance. It is also possible to improve the hydrophilicity of the surface of the ultrafiltration membrane by anchoring hydrophilic nanofibers, which results in improved water flux.290 Contrary to this, a hydrophobic surface can also be made, which is required for oil/water separation. PVDF electrospun nanofiber membranes possess potential for use in membrane contactors for environmental applications such as dissolved CH4 removal from anaerobic effluents. Montero-Rocca et al. developed a fabrication protocol combining electrospinning and hot-pressing to produce hydrophobic membranes with suitable structural integrity and pore size distribution for dissolved methane recovery from water.291 This method can also be adopted for anchoring functionalized nanofibers on ultrafiltration membranes for capturing metal ions, such as REEs, during filtration.292 Kravets et al. functionalized poly(ethylene terephthalate) (PET) track-etched membranes with straight pores by depositing electrospun PVDF nanofibers, creating hybrid membranes designed for efficient water desalination.293
6. Sustainability
Membrane technologies play a major role in addressing several UN Sustainable Development Goals (SDGs) related to water, energy, and the environment, as highlighted by Ali et al.294 However, standalone membrane processes are insufficient to achieve complete resource recovery and zero liquid discharge. Integrated treatment systems are essential to enable circular economy practices, full resource recovery, and minimal environmental footprint.39 Furthermore, enhancing process efficiency and membrane durability, and employing green fabrication methods, along with tailoring membranes for specific applications and developing end-of-life recycling or remediation strategies, are requisite for ensuring long-term sustainability.39Traditional membranes often contain toxic components and are prone to fouling, posing safety and environmental risks.295 Szekely proposed twelve principles for developing green membrane materials and processes aligned with the United Nations Sustainable Development Goals (SDGs).296 These include: (1) selection of greener compounds, (2) minimize wastewater generation, (3) use of less hazardous materials, (4) minimization of constituents, (5) benign surface modification, (6) simplified processing, (7) operation under ambient conditions, (8) maximized raw material utilization, (9) ensured reproducibility, (10) robust performance, (11) scalability, and (12) cradle-to-grave sustainability. The pore-filled membranes discussed above satisfy many of these criteria, as their fabrication typically involves minimal or no toxic solvents, since many hydrogel monomers are water-soluble, and requires no multistep chemical modification. These membranes are tuneable for specific applications and exhibit faster permeation rates due to their high compatibility with the feed, minimal interfacial resistance, the proximity of ion-exchange groups confined within the pores, and the presence of a larger amount of water compared to conventional synthetic polymer membranes. Soft material engineered synthetic polymer membranes provide a promising platform for bridging material design and practical applications. By integrating flexible, adaptive polymer networks with tailored nanostructures and surface functionalities, these membranes can combine mechanical robustness with selective permeability, antifouling capability, and process responsiveness. The surface patterning and deposition of electrospun nanofibres appear to be green and promising for developing high end synthetic polymer membranes. Such hybrid designs enable precise control over transport properties, enhance operational stability, and promote the development of sustainable, high-performance membranes aligned with green chemistry principles and long-term circular economy goals.
Membrane-based wastewater treatment technologies rely on materials such as polymer membranes and housings/modules, whose lifespans are limited by fouling and operating conditions. Recycling and remediation of these end-of-life materials are crucial for long-term sustainability and minimizing environmental impact. The disposal of end-of-life membranes and modules poses significant challenges, as current practices, incineration and landfilling, are neither economically nor environmentally sustainable.297 With increasing deployment of the membrane technologies, it is obvious that the waste generation would increase manyfold, overwhelming landfills and depleting resources. Recycling membranes and using recovered materials for new membranes provide a sustainable alternative. Depending on their physicochemical properties, end-of-life membranes can be reused for similar, upgraded, or downgraded applications, thereby extending their lifespan and reducing environmental impact.39Fig. 22 illustrates the preferred hierarchy of strategies for end-of-use membrane waste management. The major desirable options for taking care of end-of-life synthetic polymer membranes are: (i) regeneration, (ii) upcycling, (iii) downcycling, and (iv) refabrication.297 Pore-filled membranes, in particular, are expected to offer greater potential for reuse and up/down cycling, although this remains largely unexplored. Since the host polymer would be unaffected and only the guest hydrogel may be deteriorated, it is possible to refabricate pore-filled membranes for their reuse with the same efficiency.
 | ||
| Fig. 22 Sustainable hierarchy for end-of-life membrane management illustrating the transition from disposal-oriented approaches to circular practices, such as reuse, repurposing, and recycling. | ||
7. Summary and future perspective
Soft material engineered synthetic polymer membranes have emerged as a tuneable multitasking platform that bridges molecular design with advanced technological applications in desalination, wastewater treatment, clean energy, and healthcare. Through molecular-scale tailoring and structural engineering, via pore-filling, surface modification, fibre reinforcement, and interface design, these systems integrate the flexibility of soft matter with the mechanical support of synthetic polymers. Pore-filled or “gel-in-shell” membranes, mostly hydrogels or functional polymers, are immobilized within porous polymer hosts, providing tunable ion transport, high conductivity, and improved stability. In general, pore-filling provides a greener and simpler fabrication route compared to conventional solvent-intensive membrane casting, enabling scalable, energy-efficient, and low-waste production. Advances in surface patterning have enhanced mass transfer and minimized concentration polarization by introducing controlled micro-topographies that generate local turbulence and reduce fouling. Electrospun nanofibre architectures have provided high surface area, interconnected porosity, and controllable morphology, improving flux and selectivity for diverse separation processes. Surface patterning or electrospun nanofibers integrated onto membrane surfaces effectively mitigate both inorganic and biological fouling through physical and interfacial control mechanisms, offering a simple, scalable alternative to complex chemical modification routes. The recent development of roll-to-roll photopolymerization processes for pore-filled membranes marks a significant step toward industrial scalability, enabling continuous and uniform production with minimal solvent use. The adaptation of different technological synergies has led to hybrid membrane systems, integrating polymers, hydrogels, and other desirable components into a unified architecture that achieves multitasking, combining separation, catalysis, sensing, or energy conversion in a single platform.The next generation of synthetic polymer membrane fabrication should consider sustainability, circularity, and multifunctionality. It is important to focus on the design of eco-friendly, recyclable materials and scalable fabrication routes that minimize waste and energy consumption. Combining bio-inspired and self-healing functionalities with AI control could lead to membranes capable of autonomous fouling resistance and performance enhancement. Incorporation of nanostructured materials such as metal organic frameworks (MOFs), MXenes, and other advanced nanomaterials into electrospun nanofibre membrane architectures can create synergistic interfacial effects that may enhance ionic conductivity, selectivity, piezoelectricity, mechanical robustness, and antifouling performance. These nanostructures modulate mass transport pathways, increase active surface functionality, and enable tuneable sorption–diffusion behaviour, thereby improving separation efficiency and extending the applicability of soft-material-based membranes to advanced processes such as selective ion transport and CO2 capture. The coupling of surface patterning with advanced manufacturing, such as 3D printing and molecular layer deposition, offers precision and scalability for customized membrane architectures.
Conflicts of interest
There are no conflicts to declare.Data availability
This review manuscript does not require a data availability statement.Acknowledgements
The author is thankful to Prof. Dr Hemlata K. Bagla, Vice Chancellor, HSNC University, Mumbai, India, for supporting this work.References
- J. Li, W.-Y. Wong and X.-m. Tao, Recent advances in soft functional materials: preparation, function and application, Nanoscale, 2020, 12, 1281–1306, 10.1039/C9NR07035D.
- P. A. Hassan, G. Verma and R. Ganguly, 1 - Soft materials - Properties and applications, Functional Materials, ed. S. Banerjee and A. K. Tyagi, Elsevier, 2012, pp. 1–59, DOI:10.1016/B978-0-12-385142-0.00001-5.
- N. Kumar, R. Gusain, S. Pandey and S. S. Ray, Hydrogel nanocomposite adsorbents and photocatalysts for sustainable water purification, Adv. Mater. Interfaces, 2023, 10, 2201375, DOI:10.1002/admi.202201375.
- Y. Guo and G. Yu, Engineering hydrogels for efficient solar desalination and water purification, Acc. Mater. Res., 2021, 2, 374–384, DOI:10.1021/accountsmr.1c00057.
- Y. Guo, J. Bae, F. Zhao and G. Yu, Functional hydrogels for next-generation batteries and supercapacitors, Trends Chem., 2019, 1(3), 335–348, DOI:10.1016/j.trechm.2019.03.005.
- Y. Guo, J. Bae, Z. Fang, P. Li, F. Zhao and G. Yu, Hydrogels and Hydrogel-derived materials for energy and water sustainability, Chem. Rev., 2020, 120, 7642–7707, DOI:10.1021/acs.chemrev.0c00345.
- S. Shakiba, C. E. Astete, S. Paudel, C. M. Sabliov, D. F. Rodrigues and S. M. Louie, Emerging investigator series: polymeric nanocarriers for agricultural applications: synthesis, characterization, and environmental and biological interactions, Environ. Sci.: Nano, 2020, 7, 37–67, 10.1039/c9en01127g.
- C. Qin, H. Wang, Y. Zhao, Y. Qi, N. Wu, S. Zhang and W. Xu, Recent advances of hydrogel in agriculture: Synthesis, mechanism, properties and applications, Eur. Polym. J., 2024, 219, 113376, DOI:10.1016/j.eurpolymj.2024.113376.
- J. A. Hunt, R. Chen, T. van Veen and N. Bryan, Hydrogels for tissue engineering and regenerative medicine, J. Mater. Chem. B, 2014, 2(33), 5319–5338, 10.1039/C4TB00775A.
- J. Li, X. Jia and L. Yin, Hydrogel: diversity of structures and applications in food science, Food Rev. Int., 2021, 37(3), 313–372, DOI:10.1080/87559129.2020.1858313.
- D. Buenger, F. Topuz and J. Groll, Hydrogels in sensing applications, Prog. Polym. Sci., 2012, 37(12), 1678–1719, DOI:10.1016/j.progpolymsci.2012.09.001.
- B. Zhu, Q. Li, W. Zou and W. Chen, A novel method of self-healing in cementitious materials by using polyacrylic hydrogel, KSCE J. Civ. Eng., 2020, 24, 3406–3415, DOI:10.1007/s12205-020-0090-6.
- L. Peng, Y. An, H. Xiang, X. Pan, Y. Wang, Q. Yang, X. Cao, Z. L. Wang and L. Zhang, Liquid metal complexing Fe3O4 nanoparticles enable rapid polymerization of magnetically conductive hydrogels for various flexible electronics, Nano Energy, 2024, 130, 110058, DOI:10.1016/j.nanoen.2024.110058.
- S. Das, A. K. Pandey, A. A. Athawale and V. K. Manchanda, Adsorptive preconcentration of uranium in hydrogels from seawater and aqueous solutions, Ind. Eng. Chem. Res., 2009, 48, 6789–6796, DOI:10.1021/ie801912n.
- S. Chappa, S. Das, A. K. Debnath, M. Sahu, M. K. Saxena and A. K. Pandey, Spacer monomer in polymer chain influencing affinity of ethylene glycol methacrylate phosphate toward UO22+ and Pu4+ ions, Ind. Eng. Chem. Res., 2016, 55, 8992–9002, DOI:10.1021/acs.iecr.6b01534.
- A. G. Fane, R. Wang and M. X. Hu, Synthetic membranes for water purification: status and future, Angew. Chem., Int. Ed., 2015, 54, 3368–3386, DOI:10.1002/anie.201409783.
- J. Kamcev and B. D. Freeman, Charged polymer membranes for environmental/energy applications, Annu. Rev. Chem. Biomol. Eng., 2016, 7, 111–133, DOI:10.1146/annurev-chembioeng-080615-033533.
- S. Thadepalli, Review of multifarious applications of polymers in medical and health care textiles, Mater. Today: Proc., 2022, 55, 330–336, DOI:10.1016/j.matpr.2021.07.513.
- S. Correa, A. K. Grosskopf, H. L. Hernandez, D. Chan, A. C. Yu, L. M. Stapleton and E. A. Appel, Translational applications of hydrogels, Chem. Rev., 2021, 121, 11385–11457, DOI:10.1021/acs.chemrev.0c01177.
- Y. Shi, A. Feng, S. Mao, C. Onggowarsito, X. S. Zhang, W. Guo and Q. Fu, Hydrogels in solar-driven water and energy production: Recent advances and future perspectives, Chem. Eng. J., 2024, 492, 152303, DOI:10.1016/j.cej.2024.152303.
- Q. Li, B. Tian, G. Tang, H. Zhan, J. Liang, P. Guo, Q. Liu and W. Wu, Multifunctional conductive hydrogels for wearable sensors and supercapacitors, J. Mater. Chem. A, 2024, 12, 3589–3600, 10.1039/D3TA06771H.
- Y. Wang, X. Sun, Q. Liu and G. Yu, Functional gel materials for next-generation electrochromic devices and applications, Chem. Soc. Rev., 2025, 54, 3475–3512, 10.1039/D4CS01256A.
- Q. Yang, N. Adrus, F. Tomicki and M. Ulbricht, Composites of functional polymeric hydrogels and porous membranes, J. Mater. Chem., 2011, 21, 2783–2811, 10.1039/c0jm02234a.
- L. E. Beckett, J. T. Lewis, T. K. Tonge and L. T. J. Korley, Enhancement of the mechanical properties of hydrogels with continuous fibrous reinforcement, ACS Biomater. Sci. Eng., 2020, 6, 5453–5473, DOI:10.1021/acsbiomaterials.0c00911.
- A. K. Pandey, R. F. Childs, M. West, J. N. A. Lott, B. E. McCarry and J. M. Dickson, Formation of pore-filled ion-exchange membranes with in-situ cross-linking: Poly(vinylbenzyl ammonium salt)-filled membrane, J. Polym. Sci., Part A: Polym. Chem., 2001, 39, 807–820, DOI:10.1002/1099-0518(20010315)39:6<807::AID-POLA1054>3.0.CO;2-2.
- C. Agarwal, A. K. Pandey, S. Chaudhury, V. T. Aher, A. K. Patra, P. U. Sastry and A. Goswami, Ionic transport in polyelectrolyte-filled cation-exchange membranes, J. Membr. Sci., 2013, 446, 125–131, DOI:10.1016/j.memsci.2013.06.046.
- C. Agarwal, A. K. Pandey, S. Das, M. K. Sharma, D. Pattyn, P. Ares and A. Goswami, Neck-size distributions of through-pores in polymer membranes, J. Membr. Sci., 2012, 415–416, 608–615, DOI:10.1016/j.memsci.2012.05.055.
- Y. Tang, B. Tang and P. Wu, Preparation of a positively charged nanofiltration membrane based on hydrophilic-hydrophobic transformation of a poly(ionic liquid), J. Mater. Chem. A, 2015, 3, 12367–12376, 10.1039/C5TA01823D.
- J.-H. Park, Y. Park, T.-S. Jeon, Y. Seo and J.-S. Park, Impact of cross-linking-monomer characteristics on pore-filling-membrane performance and durability in anion-exchange water electrolysis, Appl. Sci., 2025, 15, 1495, DOI:10.3390/app15031495.
- R. F. Childs, A. M. Mika, A. K. Pandey, C. McCrory, S. Mouton and J. M. Dickson, Nanofiltration using pore-filled membranes: Effect of polyelectrolyte composition on performance, Sep. Purif. Technol., 2001, 22–23, 507–517, DOI:10.1016/S1383-5866(00)00172-6.
- A. K. Pandey, M. M. Gautam, J. P. Shukla and R. H. Iyer, Effect of pore characteristics on carrier-facilitated transport of Am(III) across track-etched membranes, J. Membr. Sci., 2001, 190, 9–20, DOI:10.1016/S0376-7388(01)00367-2.
- A. Goswami, A. Acharya and A. K. Pandey, Study of self-diffusion of monovalent and divalent cations in Nafion-117 ion-exchange membrane, J. Phys. Chem. B, 2001, 105, 9196–9201, DOI:10.1021/jp010529y.
- G. Suresh, Y. M. Scindia, A. K. Pandey and A. Goswami, Isotopic and ion-exchange kinetics in the Nafion-117 membrane, J. Phys. Chem. B, 2004, 108, 4104–4110, DOI:10.1021/jp037058v.
- C. Agarwal and A. K. Pandey, Remediation and recycling of inorganic acids and their green alternatives for sustainable industrial chemical processes, Environ. Sci.: Adv., 2023, 2, 1306–1339, 10.1039/d3va00112a.
- M.-S. Lee, H.-K. Kim, C.-S. Kim, H.-Y. Suh, K.-S. Nahm and Y.-W. Choi, Thin pore-filled ion exchange membranes for high power density in reverse electrodialysis: Effects of structure on resistance, stability, and ion selectivity, ChemistrySelect, 2017, 2, 1974–1978, DOI:10.1002/slct.201700167.
- K. S. Glavatskiy and S. K. Bhatia, Effect of pore size on the interfacial resistance of a porous membrane, J. Membr. Sci., 2017, 524, 738–745, DOI:10.1016/j.memsci.2016.11.062.
- Y. M. Scindia, A. K. Pandey and A. V. R. Reddy, Coupled-diffusion transport of Cr(VI) across anion-exchange membranes prepared by physical and chemical immobilization methods, J. Membr. Sci., 2005, 249, 143–152, DOI:10.1016/j.memsci.2004.10.015.
- B. Wang, J. Yan, H. Wang, R. Li, R. Fu, C. Jiang, V. Nikonenko, N. Pismenskaya, Y. Wang and T. Xu, Solvent-free fabrication of pore-filling cation-exchange membranes for highly efficient desalination, Chem. Eng. Sci., 2024, 287, 119782, DOI:10.1016/j.ces.2024.119782.
- A. K. Pandey, Sustainable water management through integrated technologies and circular resource recovery, Environ. Sci.: Water Res. Technol., 2025, 11, 1822–1846, 10.1039/d5ew00103j.
- M. Alemrajabi, J. Ricknell, S. Samak, R. R. Varela, J. Martinez, F. Hedman, K. Forsberg and Å. C. Rasmuson, Separation of rare-earth elements using supported liquid membrane extraction in pilot scale, Ind. Eng. Chem. Res., 2022, 61, 18475–18491, DOI:10.1021/acs.iecr.2c03268.
- M. A. Malik, M. A. Hashim and F. Nabi, Ionic liquids in supported liquid membrane technology, Chem. Eng. J., 2011, 171, 242–254, DOI:10.1016/j.cej.2011.03.041.
- F. J. Hernández-Fernández, A. P. de los Ríos, F. Tomás-Alonso, J. M. Palacios and G. Víllora, Preparation of supported ionic liquid membranes: Influence of the ionic liquid immobilization method on their operational stability, J. Membr. Sci., 2009, 341, 172–177, DOI:10.1016/j.memsci.2009.06.003.
- P. López-Porfiri, P. Gavagni, B. S. Moore, M. González-Miquel, P. Gorgojo, M.-C. Ferrari and M. Pérez-Page, The hydrophilic nature trade-off of supported ionic liquid membranes on CO2/CH4 separation performance, J. Mater. Chem. A, 2025, 13, 13518–13531, 10.1039/d5ta00917k.
- A. Le Mong, Y. Ahn, R. Puttaswamy and D. Kim, Pore filled solid electrolytes with high ionic conduction and electrochemical stability for lithium sulfur battery, Energy Mater., 2023, 3, 300035, DOI:10.20517/energymater.2023.20.
- B. B. Hansen, S. Spittle, B. Chen, D. Poe, Y. Zhang, J. M. Klein, A. Horton, L. Adhikari, T. Zelovich, B. W. Doherty, B. Gurkan, E. J. Maginn, A. Ragauskas, M. Dadmun, T. A. Zawodzinski, G. A. Baker, M. E. Tuckerman, R. F. Savinell and J. R. Sangoro, Deep eutectic solvents: a review of fundamentals and applications, Chem. Rev., 2021, 121, 1232–1285, DOI:10.1021/acs.chemrev.0c00385.
- M. Taghizadeh, A. Taghizadeh and V. Vatanpour, Mohammad Reza Ganjali, Mohammad Reza Saeb, Deep eutectic solvents in membrane science and technology: Fundamental, preparation, application, and future perspective, Sep. Purif. Technol., 2021, 258, 118015, DOI:10.1016/j.seppur.2020.118015.
- R. Gupta, B. G. Vats, A. K. Pandey, M. K. Sharma, P. Sahu, A. K. Yadav, S. M. Ali and S. Kannan, Insight into speciation and electrochemistry of uranyl ions in deep eutectic solvents, J. Phys. Chem. B, 2020, 124, 181–189, DOI:10.1021/acs.jpcb.9b08197.
- M. Mubashir, F. N. D'Angelo and F. Gallucci, Recent advances and challenges of deep eutectic solvent based supported liquid membranes, Sep. Purif. Rev., 2022, 51, 226–244, DOI:10.1080/15422119.2021.1901742.
- Z.-T. Huang, J.-Y. Lin and M. Krajewski, Poly(vinylidene fluoride-co-hexafluoropropylene) membranes filled with deep eutectic solvent as non-flammable and flexible quasi-solid state electrolytes for high-voltage supercapacitors, Electrochim. Acta, 2025, 526, 146192, DOI:10.1016/j.electacta.2025.146192.
- B. Jiang, H. Dou, B. Wang, Y. Sun, Z. Huang, H. Bi, L. Zhang and H. Yang, Silver-based deep eutectic solvents as separation media: supported liquid membranes for facilitated olefin transport, ACS Sustainable Chem. Eng., 2017, 5, 6873–6882, DOI:10.1021/acssuschemeng.7b01092.
- R. Deng, Y. Sun, H. Bi, H. Dou, H. Yang, B. Wang, W. Tao and B. Jiang, Deep eutectic solvents as tuning media dissolving Cu+ used in facilitated transport supported liquid membrane for ethylene/ethane separation, Energy Fuels, 2017, 31, 11146–11155, DOI:10.1021/acs.energyfuels.7b01305.
- K. Xin, P. Zhou and M. v. S. Annaland, Experimental study on CO2 separation using hydrophobic deep eutectic solvent based supported liquid membranes, Sep. Purif. Technol., 2023, 310, 123129, DOI:10.1016/j.seppur.2023.123129.
- M. Beiranvand, Y. Yamini and M. M. Khataei, Hydrophobic deep eutectic solvents as new supported liquid membranes for extraction of β-blockers by hollow fiber–electromembrane extraction, J. Sep. Sci., 2025, 48, e70102, DOI:10.1002/jssc.70102.
- A. M. Mika, A. K. Pandey and R. F. Childs, Ultra-low pressure water softening with pore-filled membranes, Desalination, 2001, 140, 265–275, DOI:10.1016/S0011-9164(01)00376-9.
- S. Suryanarayan, A. M. Mika and R. F. Childs, Gel-filled hollow fiber membranes for water softening, J. Membr. Sci., 2006, 281, 397–409, DOI:10.1016/j.memsci.2006.04.008.
- M. Y. Kim, Polyethyleneimine filled membranes, PhD Thesis, McMaster University, Hamilton, Ont., Canada, 2002 Search PubMed.
- J. M. Gohil and D. G. Karamanev, Novel pore-filled polyelectrolyte composite membranes for cathodic microbial fuel cell application, J. Power Sources, 2013, 243, 603–610, DOI:10.1016/j.jpowsour.2013.06.001.
- S.-J. Cho, Y. M. Shirke, S. J. Kwon, S. U. Hong, J. H. Kim and J.-D. Jeon, Rechargeable pore-filled composite hollow fiber membranes for water vapor separation, Sep. Purif. Technol., 2023, 320, 124223, DOI:10.1016/j.seppur.2023.124223.
- A. K. Pandey, A. Goswami, D. Sen, S. Mazumder and R. F. Childs, Formation and characterization of highly crosslinked anion-exchange membranes, J. Membr. Sci., 2003, 217, 117–130, DOI:10.1016/S0376-7388(03)00084-X.
- K. K. Gupta, S. K. Misra, S. C. Tripathi, A. Dakshinamoorthy, A. K. Pandey and A. V. R. Reddy, Facilitated transport of dibutylphosphate across fixed-site membrane, J. Membr. Sci., 2008, 318, 452–457, DOI:10.1016/j.memsci.2008.03.009.
- T. Y. Son, T.-H. Kim and S. Y. Nam, Crosslinked pore-filling anion exchange membrane using the cylindrical centrifugal force for anion exchange membrane fuel cell system, Polymers, 2020, 12, 2758, DOI:10.3390/polym12112758.
- J. Song, T. Lan, Y. Xie, D. Liu, Y. Wu, H. Ma, G. Wei, L. Wang and Z. Wang, Pore-filled composite proton exchange membrane based on crystalline poly (ether ketone) with considerable comprehensive performance in direct methanol fuel cell system, J. Power Sources, 2024, 614, 234979, DOI:10.1016/j.jpowsour.2024.234979.
- J. M. Gohil and D. G. Karamanev, Novel pore-filled polyelectrolyte composite membranes for cathodic microbial fuel cell application, J. Power Sources, 2013, 243, 603–610, DOI:10.1016/j.jpowsour.2013.06.001.
- Y. Ahn and D. Kim, High energy efficiency and stability of vanadium redox flow battery using pore-filled anion exchange membranes with ultra-low V4+ permeation, J. Ind. Eng. Chem., 2022, 110, 395–404, DOI:10.1016/j.jiec.2022.03.016.
- S.-J. Cho, Y. M. Shirke, S. J. Kwon, S. U. Hong, J. H. Kim and J.-D. Jeon, Rechargeable pore-filled composite hollow fiber membranes for water vapor separation, Sep. Purif. Technol., 2023, 320, 124223, DOI:10.1016/j.seppur.2023.124223.
- J. Fan, J. Luo and Y. Wan, Membrane chromatography for fast enzyme purification, immobilization and catalysis: A renewable biocatalytic membrane, J. Membr. Sci., 2017, 538, 68–76, DOI:10.1016/j.memsci.2017.05.053.
- H. Chang, H. Zhao, F. Qu, Z. Yan, N. Liu, M. Lu, Y. Liang, B. Lai and H. Liang, State-of-the-art insights on applications of hydrogel membranes in water and wastewater treatment, Sep. Purif. Technol., 2023, 308, 122948, DOI:10.1016/j.seppur.2022.122948.
- R. F. Childs, C. Filipe, R. Ghosh, A. M. Mika, J. Zhou, E. N. Komkova, M. Y. Kim and T. K. Dey, Composite materials comprising supported porous gels, US Pat., 8383782B2, 2013 Search PubMed.
- D. He, H. Susanto and M. Ulbricht, Photo-irradiation for preparation, modification and stimulation of polymeric membranes, Prog. Polym. Sci., 2009, 34, 62–98, DOI:10.1016/j.progpolymsci.2008.08.004.
- C. Agarwal, S. Das and A. K. Pandey, Study on pore size distributions of microporous polymer membranes having different physical architecture using capillary flow porometry, Mater. Today Chem., 2022, 23, 100652, DOI:10.1016/j.mtchem.2021.100652.
- T. Vasudevan, S. Das, A. K. Debnath and A. K. Pandey, Facilitated transport of europium(III) ions across fixed-site membrane, J. Membr. Sci., 2009, 342, 113–120, DOI:10.1016/j.memsci.2009.06.031.
- J. Zhou, R. F. Childs and A. M. Mika, Pore-filled nanofiltration membranes based on poly(2-acrylamido-2-methylpropanesulfonic acid) gels, J. Membr. Sci., 2005, 254, 89–99, DOI:10.1016/j.memsci.2004.12.043.
- T. Vasudevan, S. Das, S. Sodaye, A. K. Pandey and A. V. R. Reddy, Pore-functionalized polymer membranes for preconcentration of heavy metal ions, Talanta, 2009, 78, 171–177, DOI:10.1016/j.talanta.2008.10.053.
- T. Vasudevan, A. K. Pandey, S. Das and P. K. Pujari, Poly(ethylene glycol methacrylate phosphate-co-2-acrylamido 2-methyl-1-propane sulfonate) pore-filled substrates for heavy metal ions sorption, Chem. Eng. J., 2014, 236, 9–16, DOI:10.1016/j.cej.2013.09.064.
- W. Jiang, R. F. Childs, A. M. Mika and J. M. Dickson, Pore-filled cation-exchange membranes containing poly( styrenesulfonic acid) gels, Desalination, 2003, 159, 253–266, DOI:10.1016/S0011-9164(03)90077-4.
- K. L. Buehler and J. L. Anderson, Solvent effects on the permeability of membrane-supported gels, Ind. Eng. Chem. Res., 2002, 41, 464–472, DOI:10.1021/ie010321z.
- Y. Zhao, H. Yu, F. Xie, Y. Liu, Z. Shao and B. Yi, High durability and hydroxide ion conducting pore-filled anion exchange membranes for alkaline fuel cell applications, J. Power Sources, 2014, 269, 1–6, DOI:10.1016/j.jpowsour.2014.06.026.
- Q. Qiu, J.-H. Cha, Y.-W. Choi, J.-H. Choi, J. Shin and Y.-S. Lee, Preparation of polyethylene membranes filled with crosslinked sulfonated polystyrene for cation exchange and transport in membrane capacitive deionization process, Desalination, 2017, 417, 87–93, DOI:10.1016/j.desal.2017.05.008.
- A.-H. Bonardi, F. Bonardi, F. Morlet-Savary, C. Dietlin, G. Noirbent, T. M. Grant, J.-P. Fouassier, F. Dumur, B. H. Lessard, D. Gigmes and J. Lalevée, Photoinduced thermal polymerisation reactions, Macromolecules, 2018, 51, 8808–8820, DOI:10.1021/acs.macromol.8b01741.
- A. M. Mika, R. F. Childs, J. M. Dickson, B. E. McCarry and D. R. Gagnon, A new class of polyelectrolyte- filled microfiltration membranes with environmentally controlled porosity, J. Membr. Sci., 1995, 108, 37–56, DOI:10.1016/0376-7388(95)00140-2.
- A. M. Mika, R. F. Childs, M. West and J. N. A. Lott, Poly(4-vinylpyridine)-filled microfiltration membranes: Physicochemical properties and morphology, J. Membr. Sci., 1997, 136, 221–232, DOI:10.1016/S0376-7388(97)00171-3.
- A. M. Mika, R. F. Childs and J. M. Dickson, Salt separation and hydrodynamic permeability of a porous membrane filled with pH-sensitive gel, J. Membr. Sci., 2002, 206, 19–30, DOI:10.1016/S0376-7388(01)00474-4.
- D. M. Stachera and R. F. Childs, Tuning the acid recovery performance of poly(4-vinylpyridine)-filled membranes by the introduction of hydrophobic groups, J. Membr. Sci., 2001, 187, 213–225, DOI:10.1016/S0376-7388(01)00349-0.
- D. M. Stachera, R. F. Childs, A. M. Mika and J. M. Dickson, Acid recovery using diffusion dialysis with poly(4-vinylpyridine) filled microporous membranes, J. Membr. Sci., 1998, 148, 25–36, DOI:10.1016/S0376-7388(98)00168-9.
- D. M. Kanani, E. Komkova, T. Wong, A. Mika, R. F. Childs and R. Ghosh, Separation of human plasma proteins HSA and HIgG using high-capacity macroporous gel-filled membranes, Biochem. Eng. J., 2007, 35, 295–300, DOI:10.1016/j.bej.2007.01.034.
- F. M. Winnik, A. Momeau, A. M. Mika, R. F. Childs, A. Roig, E. Molins and R. F. Ziolo, Polyacrylic acid pore-filled membranes and their use in membrane-mediated synthesis of nanocrystalline ferrihydrite, Can. J. Chem., 1998, 76, 10–17, DOI:10.1139/v97-210.
- Z.-W. Dai, L.-S. Wan and Z.-K. Xu, Glycopolymer-filled microporous polypropylene membranes for pervaporation dehydration, J. Membr. Sci., 2010, 348, 245–251, DOI:10.1016/j.memsci.2009.11.007.
- M. Chen, M. Zhong and J. A. Johnson, Light controlled radical polymerization: mechanisms, methods, and applications, Chem. Rev., 2016, 116, 10167–10211, DOI:10.1021/acs.chemrev.5b00671.
- V. Chavan, C. Agarwal and A. K. Pandey, Pore-filled scintillating membrane as sensing matrix for α-emitting actinides, Anal. Chem., 2016, 88, 3796–3803, DOI:10.1021/acs.analchem.5b04827.
- K. Ota, S. Kikuchi, H. M. Kopel, C. E. Thanos and R. M. Nakamura, Effect of light exposure time on the depth of curing in various composite resin systems, Pediatr. Dent., 1985, 7, 19–22 CAS , PMID: 3857556.
- S. Chappa, R. N. Shinde and A. K. Pandey, Self-reducing asymmetric polymer membrane for in situ formation and containment of noble metal nanocatalysts, Green Chem., 2015, 17, 4157–4161, 10.1039/c5gc00832h.
- S. C. Yang, Y.-W. Choi, J. Choi, N. Jeong, H. Kim, H. Jeong, S. Y. Byeon, H. Yoon and Y. H. Kim, Green fabrication of pore-filling anion exchange membranes using R2R processing, J. Membr. Sci., 2019, 584, 181–190, DOI:10.1016/j.memsci.2019.04.075.
- R. N. Shinde, V. Chavan, R. Acharya, N. S. Rajurkar and A. K. Pandey, Selective removal of arsenic(V) from natural water using N-methyl-D glucamine functionalized poly(propylene) membranes, J. Environ. Chem. Eng., 2014, 2, 2221–2228, DOI:10.1016/j.jece.2014.09.018.
- Y.-C. Cao, X. Wang, M. Mamlouk and K. Scott, Preparation of alkaline anion exchange polymer membrane from methylated melamine grafted poly(vinylbenzyl chloride) and its fuel cell performance, J. Mater. Chem., 2011, 21, 12910–12916, 10.1039/C1JM12068A.
- W. Yang, J. Chen, J. Yan, S. Liu, Y. Yan and Q. Zhang, Advance of click chemistry in anion exchange membranes for energy application, J. Polym. Sci., 2022, 60, 627–649, DOI:10.1002/pol.20210819.
- L. Kang, L. Shi, L. Song and X. Guo, Facile fabrication of superhydrophobic porous materials using the water-based aza-Michael reaction for high-efficiency oil-water separation, Sep. Purif. Technol., 2023, 308, 122880, DOI:10.1016/j.seppur.2022.122880.
- O. Dumbrava, A. Filimon and L. Marin, Tailoring properties and applications of polysulfone membranes by chemical modification: Structure-properties-applications relationship, Eur. Polym. J., 2023, 196, 112316, DOI:10.1016/j.eurpolymj.2023.112316.
- J. Kim and B. V. der Bruggen, The use of nanoparticles in polymeric and ceramic membrane structures: Review of manufacturing procedures and performance improvement for water treatment, Environ. Pollut., 2010, 158, 2335–2349, DOI:10.1016/j.envpol.2010.03.024.
- S. Chappa, A. M. Mhatre, V. C. Adya and A. K. Pandey, Egg-shell membrane mimicking synthetic polymer membrane supported palladium nanoparticles for catalyzing reduction of uranyl(VI) ions, Appl. Catal., B, 2017, 203, 53–64, DOI:10.1016/j.apcatb.2016.10.004.
- S. Patra, A. N. Naik, A. K. Pandey, D. Sen, S. Mazumder and A. Goswami, Silver nanoparticles stabilized in porous polymer support: A highly active catalytic nanoreactor, Appl. Catal., A, 2016, 524, 214–222, DOI:10.1016/j.apcata.2016.07.001.
- R. Kumar, A. K. Pandey, S. V. Ramagiri and J. R. Bellare, Matrix dependent spatial distributions of in situ formed rhodium nanostructures in ion-exchange membranes, Mater. Today Chem., 2021, 22, 100610, DOI:10.1016/j.mtchem.2021.100610.
- Y. Zhao, H. Yu, F. Xie, Y. Liu, Z. Shao and B. Yi, High durability and hydroxide ion conducting pore-filled anion exchange membranes for alkaline fuel cell applications, J. Power Sources, 2014, 269, 1–6, DOI:10.1016/j.jpowsour.2014.06.026.
- S.-J. Seo, H.-J. Cha, Y. S. Kang and M.-S. Kang, Pore-filled electrolyte membranes for facile fabrication of long-term stable dye-sensitized solar cells, Electrochim. Acta, 2015, 173, 425–431, DOI:10.1016/j.electacta.2015.05.098.
- H.-B. Song, D.-H. Kim, M.-J. Lee and M.-S. Kang, Thin reinforced anion-exchange membranes for non-aqueous redox flow battery employing Fe/Co-metal complex redox species, Batteries, 2024, 10, 9, DOI:10.3390/batteries10010009.
- D.-H. Kim, J. Se, M.-J. Seo, J.-S. Lee, S.-H. Park, Y. S. Moon, Y.-W. Kang and M.-S. Choi, Pore-filled anion-exchange membranes for non-aqueous redox flow batteries with dual-metal-complex redox shuttles, J. Membr. Sci., 2014, 454, 44–50, DOI:10.1016/j.memsci.2013.11.051.
- J.-H. Lee, D.-H. Kim and M.-S. Kang, Surface-modified pore-filled anion-exchange membranes for efficient energy harvesting via reverse electrodialysis, Membranes, 2023, 13, 894, DOI:10.3390/membranes13120894.
- C. E. Duval, A. W. Darge, C. Ruff, T. A. DeVol and S. M. Husson, Rapid sample preparation for alpha spectroscopy with ultrafiltration membranes, Anal. Chem., 2018, 90, 4144–4149, DOI:10.1021/acs.analchem.8b00135.
- D.-H. Kim, Y.-E. Choi, J.-S. Park and M.-S. Kang, Capacitive deionization employing pore-filled cation-exchange membranes for energy-efficient removal of multivalent cations, Electrochim. Acta, 2019, 295, 164–172, DOI:10.1016/j.electacta.2018.10.124.
- M. Lee and J.-S. Park, Enhanced performance and durability of pore-filling membranes for anion exchange membrane water electrolysis, Membranes, 2024, 14, 269, DOI:10.3390/membranes14120269.
- V. Chavan, C. Agarwal, V. C. Adya and A. K. Pandey, Hybrid organic-inorganic anion-exchange pore-filled membranes for the recovery of nitric acid from highly acidic aqueous waste streams, Water Res., 2018, 133, 87–98, DOI:10.1016/j.watres.2018.01.023.
- S. Chappa, P. B. Rathod, A. K. Debnath, D. Sen and A. K. Pandey, Palladium nanoparticles hosted in poly (ethylenimine)and poly(ethyleneglycolmethacrylatephosphate) anchored membranes for catalyzing uranyl ions reduction and Mizoroki-Heck coupling reaction, ACS Appl. Nano Mater., 2018, 1, 3259–3268, DOI:10.1021/acsanm.8b00474.
- L. Cheng, L.-P. Zhu, P.-B. Zhang, J. Sun, B.-K. Zhu and Y.-Y. Xu, Molecular separation by poly(N-vinyl imidazole) gel-filled membranes, J. Membr. Sci., 2016, 497, 472–484, DOI:10.1016/j.memsci.2015.09.030.
- L. Cheng, M. Zhang, C. Fang, W. Feng, L. Zhu and Y. Xu, Positively charged poly (N-vinyl imidazole) gel-filled loose nanofiltration membranes: Performances and modelling analysis, J. Membr. Sci., 2021, 625, 118975, DOI:10.1016/j.memsci.2020.118975.
- R. Huang, L. K. Kostanski, C. D. M. Filipe and R. Ghosh, Environment-responsive hydrogel-based ultrafiltration membranes for protein bioseparation, J. Membr. Sci., 2009, 336, 42–49, DOI:10.1016/j.memsci.2009.03.002.
- B. Wang, J. Yan, H. Wang, R. Li, R. Fu, C. Jiang, V. Nikonenko, N. Pismenskaya, Y. Wang and T. Xu, Solvent-free fabrication of pore-filling cation-exchange membranes for highly efficient desalination, Chem. Eng. Sci., 2024, 287, 119782, DOI:10.1016/j.ces.2024.119782.
- R. Bernstein, E. Anton and M. Ulbricht, UV-photo graft functionalization of polyethersulfone membrane with strong poly electrolyte hydrogel and its application for nanofiltration, ACS Appl. Mater. Interfaces, 2012, 4, 3438–3446, DOI:10.1021/am300426c.
- Y. Qi, H. Shao, D. Luo, L. Xiang, J. Luo, Q. Tian and S. Qin, Antifouling poly(vinylidene fluoride) hollow fiber membrane with hydrophilic surfaces by ultrasonic wave-assisted graft polymerization, Polym. Eng. Sci., 2019, 59, E446–E454, DOI:10.1002/pen.25012.
- H. Shao, Y. Qi, S. Liang, S. Qin and J. Yu, Polypropylene composite hollow fiber ultrafiltration membranes with an acrylic hydrogel surface by in situ ultrasonic wave-assisted polymerization for dye removal, J. Appl. Polym. Sci., 2019, 136, 47099, DOI:10.1002/app.47099.
- H. Shao, F. Wei, D. Luo, K. Zhang, S. Liang, Q. Tian, S. Qin and J. Yu, Improving the antifouling property of polypropylene hollow fiber membranes by in situ ultrasonic wave-assisted polymerization of styrene and maleic anhydride, Polym. Eng. Sci., 2019, 59, E51–E58, DOI:10.1002/pen.24843.
- H. Shao, Y. Qi, S. Liang, S. Qin and J. Yu, Interface engineering of polypropylene hollow fiber membrane through ultrasonic capillary effect and nucleophilic substitution, Polym. Adv. Technol., 2018, 29, 3125–3133, DOI:10.1002/pat.4433.
- S. Ravi-Kumar, B. Lies, X. Zhang, H. Lyu and H. Qin, Laser ablation of polymers: a review, Polym. Int., 2019, 68, 1391–1401, DOI:10.1002/pi.5834.
- W. Li and E. Sancaktar, Patterned perforation of polyester films by excimer laser ablation, J. Laser Appl., 2017, 29, 012016, DOI:10.2351/1.4973402.
- E. Catiker, K. S. Stakleff, K. B. Carr and E. Sancaktar, Laser perforated polymer films for possible use in tissue engineering, Surf. Innovations, 2016, 4, 23–32, DOI:10.1680/jsuin.15.00019.
- C. A. Brayfield, K. G. Marra, J. P. Leonard, X. T. Cui and J. C. Gerlach, Excimer laser channel creation in polyethersulfone hollow fibers for compartmentalized in vitro neuronal cell culture scaffolds, Acta Biomater., 2008, 4, 244–255, DOI:10.1016/j.actbio.2007.10.004.
- S. Mohammadtaheri, B. Jaleh, B. F. Mohazzab, M. Eslamipanah, M. Nasrollahzadeh and R. S. Varma, Greener hydrophilicity improvement of polypropylene membrane by ArF excimer laser treatment, Surf. Coat. Technol., 2020, 399, 126198, DOI:10.1016/j.surfcoat.2020.126198.
- E. Sancaktar, Using excimer laser for manufacturing stimuli responsive membranes, Membranes, 2023, 13, 398, DOI:10.3390/membranes13040398.
- R. S. Patil and E. Sancaktar, Effect of solution parameters on pH-response of polyacrylic acid grafted polyimide smart membrane fabricated using 248 nm krypton fluoride excimer laser, Polymer, 2021, 233, 124181, DOI:10.1016/j.polymer.2021.124181.
- L. Wu and E. Sancaktar, Effect of PET support membrane thickness on water permeation behavior of thermally responsive PNIPAM-g-PET membranes, J. Membr. Sci., 2020, 610, 118304, DOI:10.1016/j.memsci.2020.118304.
- A. Tiwari and E. Sancaktar, Poly(N-isopropylacrylamide) grafted temperature responsive PET membranes: An ultrafast method for membrane processing using KrF excimer laser at 248nm, J. Membr. Sci., 2018, 552, 357–366, DOI:10.1016/j.memsci.2018.02.017.
- R. S. Patil, Erol Sancaktar, Fabrication of pH-responsive polyimide polyacrylic acid smart gating membranes: Ultrafast method using 248 nm krypton fluoride excimer laser, ACS Appl. Mater. Interfaces, 2021, 13, 24431–24441, DOI:10.1021/acsami.1c01265.
- R. Patil, A. Narayanan, C. Tantisuwanno and E. Sancaktar, Immobilization of glucose oxidase on pH-responsive polyimide polyacrylic acid smart membranes fabricated using 248 nm KrF excimer laser for drug delivery, Biointerface Res. Appl. Chem., 2023, 13, 11, DOI:10.33263/BRIAC131.011.
- V. H. Pino-Ramos, A. Ramos-Ballesteros, F. López-Saucedo, J. E. López-Barriguete, G. H. C. Varca and E. Bucio, Radiation grafting for the functionalization and development of smart polymeric materials, Top. Curr. Chem., 2016, 374, 63, DOI:10.1007/s41061-016-0063-x.
- M. M. Nasef, Radiation-grafted membranes for polymer electrolyte fuel cells: Current trends and future directions, Chem. Rev., 2014, 114, 12278–12329, DOI:10.1021/cr4005499.
- M. M. Nasef and A. El-S, Preparation and applications of ion exchange membranes by radiation-induced graft copolymerization of polar monomers onto non-polar films, Prog. Polym. Sci., 2004, 29, 499–561, DOI:10.1016/j.progpolymsci.2004.01.003.
- M. M. Nasef and O. Güven, Radiation-grafted copolymers for separation and purification purposes: Status, challenges and future directions, Prog. Polym. Sci., 2012, 37, 1597–1656, DOI:10.1016/j.progpolymsci.2012.07.004.
- R. F. Khedr, Radiation-grafting on polypropylene copolymer membranes for using in cadmium adsorption, Polymers, 2023, 15, 686, DOI:10.3390/polym15030686.
- J. Ma, J. Peng and M. Zhai, Chapter Seven - Radiation-Grafted Membranes for Applications in Renewable Energy Technology, Rad. Technol. Adv. Mater., ed. G. Wu, M. Zhai and M. Wang, Academic Press, 2019, pp. 207–247, DOI:10.1016/B978-0-12-814017-8.00007-X.
- Z. Jia, T. Zhen, X. Zhang and Q. Gu, Preparation of phase-transfer catalytic porous membrane by γ-ray irradiation grafting and its application in nucleophilic substitution reaction, J. Membr. Sci., 2013, 448, 74–80, DOI:10.1016/j.memsci.2013.07.056.
- L. Wang, X. Peng, W. E. Mustain and J. R. Varcoe, Radiation-grafted anion-exchange membranes: the switch from low- to high-density polyethylene leads to remarkably enhanced fuel cell performance, Energy Environ. Sci., 2019, 12, 1575–1579, 10.1039/c9ee00331b.
- A. Albert, A. O. Barnett, M. S. Thomassen, T. J. Schmidt and L. Gubler, Radiation-grafted polymer electrolyte membranes for water electrolysis cells: Evaluation of key membrane properties, ACS Appl. Mater. Interfaces, 2015, 7, 22203–22212, DOI:10.1021/acsami.5b04618.
- A. C. Kırlıoğlu, N. R. Mojarrad, S. A. Gürsel, E. Güler and B. Y. Kaplan, New generation radiation-grafted PVDF-g-VBC based dual-fiber electrospun anion exchange membranes, Int. J. Hydrogen Energy, 2024, 51, 1390–1401, DOI:10.1016/j.ijhydene.2023.05.345.
- H. Ma, J. Liu, H. Hua, L. Peng, X. Shen, X. Wang, P. Zhang and J. Zhao, Facile fabrication of functionalized separators for lithium-ion batteries with ionic conduction path modifications via the γ-ray co-irradiation grafting process, ACS Appl. Mater. Interfaces, 2021, 13, 27663–27673, DOI:10.1021/acsami.1c06460.
- Z. Wang, J. Jiang, Z. Dong, Y. Song and L. Zhao, Radiation synthesis of imidazolium ionic liquid grafted PVDF as the anion exchange membrane for vanadium redox flow batteries, New J. Chem., 2023, 47, 8013–8021, 10.1039/D2NJ05386A.
- L. Wang, E. Magliocca, E. L. Cunningham, W. E. Mustain, S. D. Poynton, R. Escudero-Cid, M. M. Nasef, J. Ponce-González, R. Bance-Souahli, R. C. T. Slade, D. K. Whelligan and J. R. Varcoe, An optimised synthesis of high performance radiation-grafted anion-exchange membranes, Green Chem., 2017, 19, 831–843, 10.1039/c6gc02526a.
- V. Kumar, N. Misra, N. K. Goel, R. Thakar, J. Gupta and L. Varshney, A horseradish peroxidase immobilized radiation grafted polymer matrix: a biocatalytic system for dye waste water treatment, RSC Adv., 2016, 6, 2974–2981, 10.1039/C5RA20513A.
- L. Shen, S. Feng, J. Li, J. Chen, F. Li, H. Lin and G. Yu, Surface modification of polyvinylidene fluoride (PVDF) membrane via radiation grafting: novel mechanisms underlying the interesting enhanced membrane performance, Sci. Rep., 2017, 7, 2721, DOI:10.1038/s41598-017-02605-3.
- J. Cui and A. del Campo, Multivalent H-bonds for self-healing hydrogels, Chem. Commun., 2012, 48, 9302–9304, 10.1039/C2CC34701F.
- D. C. Tuncaboylu, A. Argun, M. P. Algi and O. Okay, Autonomic self-healing in covalently crosslinked hydrogels containing hydrophobic domains, Polymer, 2013, 54, 6381–6388, DOI:10.1016/j.polymer.2013.09.051.
- H. Liu, C. Xiong, Z. Tao, Y. Fan, X. Tang and H. Yang, Zwitterionic copolymer-based and hydrogen bonding-strengthened self-healing hydrogel, RSC Adv., 2015, 5, 33083–33088, 10.1039/C4RA15003A.
- B. A. Getachew, S.-R. Kim and J.-H. Kim, Self-Healing hydrogel pore-filled water filtration membranes, Environ. Sci. Technol., 2017, 51, 905–913, DOI:10.1021/acs.est.6b04574.
- B. A. Getachew, W. Guo, M. Zhong and J.-H. Kim, Asymmetric hydrogel-composite membranes with improved water permeability and self-healing property, J. Membr. Sci., 2019, 578, 196–202, DOI:10.1016/j.memsci.2019.01.022.
- B. A. Getachew, S.-R. Kim and J.-H. Kim, Improved stability of self-healing hydrogel pore-filled membranes with ionic cross-links, J. Membr. Sci., 2018, 553, 1–9, DOI:10.1016/j.memsci.2018.02.027.
- H. Jiang and S. Liu, Construction of self-healing polyethersulfone ultrafiltration membrane by cucurbit[8]uril hydrogel via RTIPS method and host-guest chemistry, Chemosphere, 2023, 311, 137079, DOI:10.1016/j.chemosphere.2022.137079.
- K. Namsheer and C. S. Rout, Conducting polymers: a comprehensive review on recent advances in synthesis, properties and applications, RSC Adv., 2021, 11, 5659–5697, 10.1039/d0ra07800j.
- A. Thadathil, H. Pradeep, D. Joshy, Y. A. Ismail and P. Periyat, Polyindole and polypyrrole as a sustainable platform for environmental remediation and sensor applications, Mater. Adv., 2022, 3, 2990–3022, 10.1039/d2ma00022a.
- M.-L. Liu, C.-X. Zhang, M.-J. Tang, S.-P. Sun, W. Xing and Y. M. Lee, Evolution of functional nanochannel membranes, Prog. Mater. Sci., 2023, 139, 101162, DOI:10.1016/j.pmatsci.2023.101162.
- T.-Z. Jia, R. Feng, C. Cui, Q. Chen, L. Cseri, R.-F. Zhou, G. Szekely, X.-L. Cao and S.-P. Sun, Conductive nanofiltration membranes via in situ PEDOT-polymerization for electro-assisted membrane fouling mitigation, Water Res., 2024, 252, 121251, DOI:10.1016/j.watres.2024.121251.
- G. A. Tishchenko, J. Dybal, J. Stejskal, V. Kůdela, M. Bleha, E. Y. Rosova and G. K. Elyashevich, Electrical resistance and diffusion permeability of microporous polyethylene membranes modified with polypyrrole and polyaniline in solutions of electrolytes, J. Membr. Sci., 2002, 196, 279–287, DOI:10.1016/S0376-7388(01)00607-X.
- A. Kros, R. J. M. Nolte and N. A. J. M. Sommerdijk, Conducting polymers with confined dimensions: Track-etch membranes for amperometric biosensor applications, Adv. Mater., 2002, 14, 1779–1782, DOI:10.1002/1521-4095(20021203)14:23<1779::AID-ADMA1779>3.0.CO;2-T.
- Z. Wu, G. Zhao, X. Tang, J. Li, W. Chen and R. Li, Superhydrophilic PANI/Ag/TA@PVDF composite membrane with antifouling property for oil–water separation, Langmuir, 2024, 40, 11329–11339, DOI:10.1021/acs.langmuir.4c01229.
- X. Tan, C. Hu, Z. Zhu, H. Liu and J. Qu, Electrically pore-size-tunable polypyrrole membrane for antifouling and selective separation, Adv. Funct. Mater., 2019, 29, 1903081, DOI:10.1002/adfm.201903081.
- Z. Yuan, Q. Dai, Y. Zhao, W. Lu, X. Li and H. Zhang, J. Mater. Chem. A, 2016, 4, 12955–12962, 10.1039/C6TA05655E.
- M. Neumann, G. di Marco, D. Iudin, M. Viola, C. F. van Nostrum, B. G. P. van Ravensteijn and T. Vermonden, Stimuli-responsive hydrogels: The dynamic smart biomaterials of tomorrow, Macromolecules, 2023, 56, 8377–8392, DOI:10.1021/acs.macromol.3c00967.
- A. Pourjavadi, R. Heydarpour and Z. M. Tehrani, Multi-stimuli-responsive hydrogels and their medical applications, New J. Chem., 2021, 45, 15705–15717, 10.1039/D1NJ02260A.
- M. C. Koetting, J. T. Peters, S. D. Steichen and N. A. Peppas, Stimulus-responsive hydrogels: Theory, modern advances, and applications, Mater. Sci. Eng., R, 2015, 93, 1–49, DOI:10.1016/j.mser.2015.04.001.
- Z. Yang, L. Chen, D. J. McClements, C. Qiu, C. Li, Z. Zhang, M. Miao, Y. Tian, K. Zhu and Z. Jin, Stimulus-responsive hydrogels in food science: A review, Food Hydrocolloids, 2022, 124, 107218, DOI:10.1016/j.foodhyd.2021.107218.
- H. M. El-Husseiny, E. A. Mady, L. Hamabe, A. Abugomaa, K. Shimada, T. Yoshida, T. Tanaka, A. Yokoi, M. Elbadawy and R. Tanaka, Smart/stimuli-responsive hydrogels: Cutting-edge platforms for tissue engineering and other biomedical applications, Mater. Today Bio, 2022, 13, 100186, DOI:10.1016/j.mtbio.2021.100186.
- I. S. Protsak and Y. M. Morozov, Fundamentals and advances in stimuli-responsive hydrogels and their applications: A review, Gels, 2025, 11, 30, DOI:10.3390/gels11010030.
- T. Huang, Z. Su, K. Hou, J. Zeng, H. Zhou, L. Zhang and S. P. Nunes, Advanced stimuli-responsive membranes for smart separation, Chem. Soc. Rev., 2023, 52, 4173–4207, 10.1039/D2CS00911K.
- J. Zhang, R. Wang, X. Ou, X. Zhang, P. Liu, Z. Chen, B. Zhang, C. Liu, S. Zhao, Z. Chen, J. Zhu, S. Lu and P. Zhang, Bio-inspired synthesis of thermo-responsive imprinted composite membranes for selective recognition and separation of ReO4−, Sep. Purif. Technol., 2021, 259, 118165, DOI:10.1016/j.seppur.2020.118165.
- Z. Liu, F. Luo, X.-J. Ju, R. Xie, T. Luo, Y.-M. Sun and L.-Y. Chu, Positively K+-responsive membranes with functional gates driven by host-guest molecular recognition, Adv. Funct. Mater., 2012, 22, 4742–4750, DOI:10.1002/adfm.201201251.
- J.-B. Qu, L.-Y. Chu, M. Yang, R. Xie, L. Hu and W.-M. Chen, A pH-responsive gating membrane system with pumping effects for improved controlled release, Adv. Funct. Mater., 2006, 16, 1865–1872, DOI:10.1002/adfm.200500897.
- N. Adrus and M. Ulbricht, Novel hydrogel pore-filled composite membranes with tunable and temperature-responsive size-selectivity, J. Mater. Chem., 2012, 22, 3088–3098, 10.1039/C2JM15022K.
- I. B. Muslimova, Z. K. Zhatkanbayeva, D. D. Omertasov, G. B. Melnikova, A. B. Yeszhanov, O. Güven, S. A. Chizhik, M. V. Zdorovets and I. V. Korolkov, Stimuli-responsive track-etched membranes for separation of water-oil emulsions, Membranes, 2023, 13, 523, DOI:10.3390/membranes13050523.
- L. Dong, W. Fan, H. Zhang, M. Chen and Y. Zhao, CO2-Responsive polymer membranes with gas-tunable pore size, Chem. Commun., 2017, 53, 9574–9577, 10.1039/C7CC05291J.
- Z. Chen, H.-Y. Xie, Y.-J. Li, G.-E. Chen, S.-J. Xu and Z.-L. Xu, Smart light responsive polypropylene membrane switching reversibly between hydrophobicity and hydrophilicity for oily water separation, J. Membr. Sci., 2021, 638, 119704, DOI:10.1016/j.memsci.2021.119704.
- L. Baumann, K. Schöller, D. de Courten, D. Marti, M. Frenz, M. Wolf, R. M. Rossi and L. J. Scherer, Development of light-responsive porous polycarbonate membranes for controlled caffeine delivery, RSC Adv., 2013, 3, 23317–23326, 10.1039/C3RA44399J.
- X. Lin, R. Huang and M. Ulbricht, Novel magneto-responsive membrane for remote control switchable molecular sieving, J. Mater. Chem. B, 2016, 4, 867–879, 10.1039/C5TB02368H.
- X. Zhao, X. Chen, H. Yuk, S. Lin, X. Liu and G. Parada, Soft materials by design: Unconventional polymer networks give extreme properties, Chem. Rev., 2021, 121, 4309–4372, DOI:10.1021/acs.chemrev.0c01088.
- A. Agrawal, N. Rahbar and P. D. Calvert, Strong fiber-reinforced hydrogel, Acta Biomater., 2013, 9, 5313–5318, DOI:10.1016/j.actbio.2012.10.011.
- B. Pei, W. Wang, Y. Fan, X. Wang, F. Watari and X. Li, Fiber-reinforced scaffolds in soft tissue engineering, Regener. Biomater., 2017, 4, 257–268, DOI:10.1093/rb/rbx021.
- B. Niemczyk-Soczynska, A. Zaszczyńska, K. Zabielski and P. Sajkiewicz, Hydrogel, electrospun and composite materials for bone/cartilage and neural tissue engineering, Materials, 2021, 14, 6899, DOI:10.3390/ma14226899.
- L. A. Bosworth, L.-A. Turner and S. H. Cartmell, State of the art composites comprising electrospun fibres coupled with hydrogels: a review, Nanomedicine, 2013, 9, 322–335, DOI:10.1016/j.nano.2012.10.008.
- M. Zhang, S. Xu, R. Wang, Y. Che, C. Han, W. Feng, C. Wang and W. Zhao, Electrospun nanofiber/hydrogel composite materials and their tissue engineering applications, J. Mater. Sci. Technol., 2023, 162, 157–178, DOI:10.1016/j.jmst.2023.04.015.
- Y. Li, J. Wang, Y. Wang and W. Cui, Advanced electrospun hydrogel fibers for wound healing, Composites, Part B, 2021, 223, 109101, DOI:10.1016/j.compositesb.2021.109101.
- L. E. Beckett, J. T. Lewis, T. K. Tonge and L. T. J. Korley, Enhancement of the mechanical properties of hydrogels with continuous fibrous reinforcement, ACS Biomater. Sci. Eng., 2020, 6, 5453–5473, DOI:10.1021/acsbiomaterials.0c00911.
- Y. J. No, S. Tarafder, B. Reischl, Y. Ramaswamy, C. Dunstan, O. Friedrich, C. H. Lee and H. Zreiqat, High-strength fiber-reinforced composite hydrogel scaffolds as biosynthetic tendon graft material, ACS Biomater. Sci. Eng., 2020, 6, 1887–1898, DOI:10.1021/acsbiomaterials.9b01716.
- N. Moghimi, M. Kamaraj, F. Zehtabi, S. A. Yavari, M. Kohandel, A. Khademhosseini and J. V. John, Development of bioactive short fiber-reinforced printable hydrogels with tunable mechanical and osteogenic properties for bone repair, J. Mater. Chem. B, 2024, 12, 2818–2830, 10.1039/D3TB02924G.
- M. Castilho, G. Hochleitner, W. Wilson, B. van Rietbergen, P. D. Dalton, J. Groll, J. Malda and K. Ito, Mechanical behavior of a soft hydrogel reinforced with three-dimensional printed microfibre scaffolds, Sci. Rep., 2018, 8, 1245, DOI:10.1038/s41598-018-19502-y.
- A. M. Jordan, S.-E. Kim, K. V. de Voorde, J. K. Pokorski and L. T. J. Korley, In situ fabrication of fiber reinforced three-dimensional hydrogel tissue engineering scaffolds, ACS Biomater. Sci. Eng., 2017, 3, 1869–1879, DOI:10.1021/acsbiomaterials.7b00229.
- J. MacKenzie, E. Siren, M. Daneshi, R. Melnick, T. Treskatis, A. Wachs, J. N. Kizhakkedathu and D. M. Martinez, Fibre-reinforced biocompatible hydrogel to replace single-use plastic tubing in the clinical setting, Chem. Eng. J., 2022, 428, 131786, DOI:10.1016/j.cej.2021.131786.
- J. Visser, F. P. W. Melchels, J. E. Jeon, E. M. van Bussel, L. S. Kimpton, H. M. Byrne, W. J. A. Dhert, P. D. Dalton, D. W. Hutmacher and J. Malda, Reinforcement of hydrogels using three-dimensionally printed microfibres, Nat. Commun., 2015, 6, 6933, DOI:10.1038/ncomms7933.
- A. Martin, J. N. Nyman, R. Reinholdt, J. Cai, A.-L. Schaedel, M. J. A. van der Plas, M. Malmsten, T. Rades and A. Heinz, In Situ Transformation of electrospun nanofibers into nanofiber reinforced hydrogels, Nanomaterials, 2022, 12, 2437, DOI:10.3390/nano12142437.
- B. Kong, Y. Chen, R. Liu, X. Liu, C. Liu, Z. Shao, L. Xiong, X. Liu, W. Sun and S. Mi, Fiber reinforced GelMA hydrogel to induce the regeneration of corneal stroma, Nat. Commun., 2020, 11, 1435, DOI:10.1038/s41467-020-14887-9.
- S. Tang, Z. Davoudi, G. Wang, Z. Xu, T. Rehman, A. Prominski, B. Tian, K. M. Bratlie, H. Peng and Q. Wang, Soft materials as biological and artificial membranes, Chem. Soc. Rev., 2021, 50, 12679–12701, 10.1039/d1cs00029b.
- Z.-Y. Ma, Y.-R. Xue, H.-C. Yang, J. Wu and Z.-K. Xu, Surface and interface engineering of polymer membranes: Where we are and where to go, Macromolecules, 2022, 55, 3363–3383, DOI:10.1021/acs.macromol.1c02647.
- L. Upadhyaya, X. Qian and S. R. Wickramasinghe, Chemical modification of membrane surface- Overview, Curr. Opin. Chem. Eng., 2018, 20, 13–18, DOI:10.1016/j.coche.2018.01.002.
- W. A. Laftah and W. A. W. A. Rahman, Polymers for anti-fouling applications: A review, Environ. Sci.: Adv., 2025, 4, 824–841, 10.1039/d5va00034c.
- K. C. Khulbe, C. Feng and T. Matsuura, The art of surface modification of synthetic polymeric membranes, J. Appl. Polym. Sci., 2010, 115, 855–895, DOI:10.1002/app.31108.
- L.-S. Wan, Z.-M. Liu and Z.-K. Xu, Surface engineering of macroporous polypropylene membranes, Soft Matter, 2009, 5, 1775–1785, 10.1039/B813600A.
- M. S. Siddique, Q. Song, X. Xiong, H. Fareed, N. Graham and W. Yu, Hydrolyzed polyacrylonitrile UF-membrane for surface and TAP water treatment: Influence on DBPs formation and removal, Chem. Eng. J., 2023, 471, 144314, DOI:10.1016/j.cej.2023.144314.
- Q. Wang, W. Lin, S. Chou, P. Dai and X. Huang, Patterned membranes for improving hydrodynamic properties and mitigating membrane fouling in water treatment: A review, Water Res., 2023, 236, 119943, DOI:10.1016/j.watres.2023.119943.
- Z. R. Usha, Surface-modified polymeric membrane-based separation technology with super-wetting properties for sustainable oily wastewater separation: A cutting-edge review, Sep. Purif. Technol., 2026, 380, 135219, DOI:10.1016/j.seppur.2025.135219.
- O. Heinz, M. Aghajani, A. R. Greenberg and Y. Ding, Surface-patterning of polymeric membranes: fabrication and performance, Curr. Opin. Chem. Eng., 2018, 20, 1–12, DOI:10.1016/j.coche.2018.01.008.
- Y. Ibrahim and N. Hilal, A critical assessment of surface-patterned membranes and their role in advancing membrane technologies, ACS ES&T Water, 2023, 3, 3807–3834, DOI:10.1021/acsestwater.3c00564.
- A. Mitranescu, M. Patel, S. Panglisch, J. E. Drewes and I. M. A. ElSherbiny, Surface-patterned water separation membranes: A critical analysis of current knowledge and future research needs, ACS ES&T Water, 2024, 4, 5225–5242, DOI:10.1021/acsestwater.4c00779.
- N. U. Barambu, M. R. Bilad, Y. Wibisono, J. Jaafar, T. M. I. Mahlia and A. L. Khan, Membrane surface patterning as a fouling mitigation strategy in liquid filtration: A review, Polymers, 2019, 11, 1687, DOI:10.3390/polym11101687.
- Y. Liu, D. Nakamura, J. Gao, K. Imamura, S. Aki, Y. Nagai, I. Taniguchi, K. Fujiwara, R. Horii, Y. Miura and Y. Hoshino, Laser patterning of porous support membranes to enhance the effective surface area of thin-film composite-facilitated transport membranes for CO2 separation, ACS Appl. Mater. Interfaces, 2024, 16, 29112–29120, DOI:10.1021/acsami.4c01260.
- D. Choi, W. Lee, Y. Lee, D.-N. Kim, J. Park and W.-G. Koh, Fabrication of macroporous hydrogel membranes using photolithography for enzyme immobilization, J. Chem. Technol. Biotechnol., 2008, 83, 252–259, DOI:10.1002/jctb.1800.
- Y. Ding, S. Maruf, M. Aghajani and A. R. Greenberg, Surface patterning of polymeric membranes and its effect on antifouling characteristics, Sep. Sci. Technol., 2016, 52, 240–257, DOI:10.1080/01496395.2016.1201115.
- F. Khelifa, S. Ershov, Y. Habibi, R. Snyders and P. Dubois, Free-radical-induced grafting from plasma polymer surfaces, Chem. Rev., 2016, 116, 3975–4005, DOI:10.1021/acs.chemrev.5b00634.
- D. J. Miller, D. R. Dreyer, C. W. Bielawski, D. R. Paul and B. D. Freeman, Surface modification of water purification membranes, Angew. Chem., Int. Ed., 2017, 56, 4662–4711, DOI:10.1002/anie.201601509.
- A. Szymczyk, B. van der Bruggen and M. Ulbricht, Chapter 13: Surface modification of water purification membranes, in Surface Modification of Polymers, ed. J. Pinson and D. Thiry, Wiley, 2019, DOI:10.1002/9783527819249.ch13.
- Y.-M. Ko, D.-Y. Choi, S.-C. Jung and B.-H. Kim, Characteristics of plasma treated electrospun polycaprolactone (PCL) nanofiber scaffold for bone tissue engineering, J. Nanosci. Nanotechnol., 2015, 15, 192–195, DOI:10.1166/jnn.2015.8372.
- M. Parvinzadeh Gashti, D. Hegemann, M. Stir and J. Hulliger, Thin film plasma functionalization of polyethylene terephthalate to induce bone-like hydroxyapatite nanocrystals, Plasma Processes Polym., 2014, 11, 37–43, DOI:10.1002/ppap.201300100.
- P. Chytrosz-Wrobel, M. Golda-Cepa, E. Stodolak-Zych, J. Rysz and A. Kotarba, Effect of oxygen plasma-treatment on surface functional groups, wettability, and nanotopography features of medically relevant polymers with various crystallinities, Appl. Surf. Sci. Adv., 2023, 18, 100497, DOI:10.1016/j.apsadv.2023.100497.
- M. Gryta and W. Tomczak, Stability of Ar/O2 plasma-treated polypropylene membranes applied for membrane distillation, Membranes, 2021, 11, 531, DOI:10.3390/membranes11070531.
- B. Á. Ádám, S. Spátay, B. Jávor, S. László, L. Illés, P. Fürjes, T. Tóth, P. Huszthy and Á. Golcs, Atmospheric air plasma pre-activation and customizable covalent functionalization of PVDF-membranes of microtiter filter plates, Sci. Rep., 2025, 15, 3238, DOI:10.1038/s41598-024-85040-5.
- K. S. Kim, K. H. Lee, K. Cho and C. E. Park, Surface modification of polysulfone ultrafiltration membrane by oxygen plasma treatment, J. Membr. Sci., 2002, 199, 135–145, DOI:10.1016/S0376-7388(01)00686-X.
- K. R. Kull, M. L. Steen and E. R. Fisher, Surface modification with nitrogen-containing plasmas to produce hydrophilic, low-fouling membranes, J. Membr. Sci., 2005, 246, 203–215, DOI:10.1016/j.memsci.2004.08.019.
- L. Cheng, R. Ghobeira, P. Cools, Z. Liu, K. Yan, N. De Geyter and R. Morent, Comparative study of different nitrogen-containing plasma modifications applied on 3D porous PCL scaffolds and 2D PCL films, Appl. Surf. Sci., 2020, 516, 146067, DOI:10.1016/j.apsusc.2020.146067.
- T. Hazarika, B. Kakati, D. Pal, R. Saikia, A. Rawal, M. K. Mahanta and S. Biswas, Role of plasma process gas on permeate flux augmentation of cellulose nitrate membrane for mud water treatment, Sci. Rep., 2024, 14, 6585, DOI:10.1038/s41598-024-56948-9.
- J. Wang, X. Chen, R. Reis, Z. Chen, N. Milne, B. Winther-Jensen, L. Kong and L. F. Dumée, Plasma modification and synthesis of membrane materials-A mechanistic review, Membranes, 2018, 8, 56, DOI:10.3390/membranes8030056.
- D. S. Wavhal and E. R. Fisher, Modification of polysulfone ultrafiltration membranes by CO2 plasma treatment, Desalination, 2005, 172, 189–205, DOI:10.1016/j.desal.2004.06.201.
- J. O. Zoppe, N. C. Ataman, P. Mocny, J. Wang, J. Moraes and H.-A. Klok, Surface-initiated controlled radical polymerization: state-of-the-art, opportunities, and challenges in surface and interface engineering with polymer brushes, Chem. Rev., 2017, 117, 1105–1318, DOI:10.1021/acs.chemrev.6b00314.
- M. K. Hadi, X. Wang, Y. Peng, S. Sangaraju and F. Ran, Functional polymeric membrane materials: a perspective from versatile methods and modification to potential applications, Polym. Sci. Technol., 2025, 1(5), 366–412, DOI:10.1021/polymscitech.4c00030.
- Z. Wang, H.-C. Yang, F. He, S. Peng, Y. Li, L. Shao and S. B. Darling, Mussel-inspired surface engineering for water-remediation materials, Matter, 2019, 1, 115–155, DOI:10.1016/j.matt.2019.05.002.
- A. Taghizadeh, M. Taghizadeh, M. K. Yazdi, P. Zarrintaj, J. D. Ramsey, F. Seidi, F. J. Stadler, H. Lee, M. R. Saeb and M. Mozafari, Mussel-inspired biomaterials: From chemistry to clinic, Bioeng. Transl. Med., 2022, 7, e10385, DOI:10.1002/btm2.10385.
- S. Chen, P. Liu, Z. Li, Y. Bi, F. Li and Y. Yu, Biomimetic mussel technology for membrane material modification: Adhesion mechanism and design strategy, J. Polym. Sci., 2023, 61, 2815–2827, DOI:10.1002/pol.20230205.
- H.-C. Yang, J. Luo, Y. Lv, P. Shen and Z.-K. Xu, Surface engineering of polymer membranes via mussel-inspired chemistry, J. Membr. Sci., 2015, 483, 42–59, DOI:10.1016/j.memsci.2015.02.027.
- H. Hemmatpour, O. De Luca, D. Crestani, M. C. A. Stuart, A. Lasorsa, P. C. A. van der Wel, K. Loos, T. Giousis, V. Haddadi-Asl and P. Rudolf, New insights in polydopamine formation via surface adsorption, Nat. Commun., 2023, 14, 664, DOI:10.1038/s41467-023-36303-8.
- S. Cui, X. Kang, W. Cai and S. Zhang, Revealing the formation mechanism of insoluble polydopamine by a simplified model system, Polym. Chem., 2017, 8, 860–864, 10.1039/C6PY02005D.
- N. R. Barros, Y. Chen, V. Hosseini, W. Wang, R. Nasiri, M. Mahmoodi, E. P. Yalcintas, R. Haghniaz, M. M. Mecwan, S. Karamikamkar, W. Dai, S. A. Sarabi, N. Falcone, P. Young, Y. Zhu, W. Sun, S. Zhang, J. Lee, K. Lee, S. Ahadian, M. R. Dokmeci, A. Khademhosseini and H.-J. Kim, Biomater. Sci., 2021, 9, 6653–6672, 10.1039/d1bm01126j.
- S. Li, J. Chen, J. Wang and H. Zeng, Anti-biofouling materials and surfaces based on mussel-inspired chemistry, Mater. Adv., 2021, 2, 2216–2230, 10.1039/d1ma00053e.
- Z. Xu, L. Li, J. Liu, C. Dai, W. Sun, J. Chen, Z. Zhu, M. Zhao and H. Zeng, Mussel-inspired superhydrophilic membrane constructed on a hydrophilic polymer network for highly efficient oil/water separation, J. Colloid Interface Sci., 2022, 608, 702–710, DOI:10.1016/j.jcis.2021.09.123.
- T.-Y. Kuo and Y.-C. Chung, Surface-initiated polymerization of mussel-inspired dopamine for hydrophilic coatings, Mater. Adv., 2021, 2, 5686–5690, 10.1039/d0ma00908c.
- H. Sun, Y. Zhang, H. Sadam, J. Ma, Y. Bai, X. Shen, J.-K. Kim and L. Shao, Novel mussel-inspired zwitterionic hydrophilic polymer to boost membrane water-treatment performance, J. Membr. Sci., 2019, 582, 1–8, DOI:10.1016/j.memsci.2019.03.086.
- Y. Xu, Z. Li, K. Su, T. Fan and L. Cao, Mussel-inspired modification of PPS membrane to separate and remove the dyes from the wastewater, Chem. Eng. J., 2018, 341, 371–382, DOI:10.1016/j.cej.2018.02.048.
- H.-C. Yang, K.-J. Liao, H. Huang, Q.-Y. Wu, L.-S. Wan and Z.-K. Xu, Mussel-inspired modification of a polymer membrane for ultra-high water permeability and oil-in-water emulsion separation, J. Mater. Chem. A, 2014, 2, 10225–10230, 10.1039/C4TA00143E.
- Z.-X. Wang, C.-H. Lau, N.-Q. Zhang, Y.-P. Bai and L. Shao, Mussel-inspired tailoring of membrane wettability for harsh water treatment, J. Mater. Chem. A, 2015, 3, 2650–2657, 10.1039/C4TA05970K.
- L. Ma, H. Qin, C. Cheng, Y. Xia, C. He, C. Nie, L. Wang and C. Zhao, Mussel-inspired self-coating at macro-interface with improved biocompatibility and bioactivity via dopamine grafted heparin-like polymers and heparin, J. Mater. Chem. B, 2014, 2, 363–375, 10.1039/C3TB21388A.
- Q. Xu, Q. Kong, Z. Liu, J. Zhang, X. Wang, R. Liu, L. Yue and G. Cui, Polydopamine-coated cellulose microfibrillated membrane as high performance lithium-ion battery separator, RSC Adv., 2014, 4, 7845–7850, 10.1039/C3RA45879B.
- G. Hong, L. Shen, M. Wang, Y. Yang, X. Wang, M. Zhu and B. S. Hsiao, Nanofibrous polydopamine complex membranes for adsorption of Lanthanum (III) ions, Chem. Eng. J., 2014, 244, 307–316, DOI:10.1016/j.cej.2014.01.073.
- D. Cui, M. Li, P. Zhang, F. Rao, W. Huang, C. Wang, W. Guo and T. Wang, Polydopamine-coated polycaprolactone electrospun nanofiber membrane loaded with thrombin for wound hemostasis, Polymers, 2023, 15, 3122, DOI:10.3390/polym15143122.
- X. Wu, Q. Jiang, D. Ghim, S. Singamaneni and Y.-S. Jun, Localized heating with a photothermal polydopamine coating facilitates a novel membrane distillation process, J. Mater. Chem. A, 2018, 6, 18799–18807, 10.1039/C8TA05738A.
- C. Zhang, B. Wu, Y. Zhou, F. Zhou, W. Liu and Z. Wang, Mussel-inspired hydrogels: from design principles to promising applications, Chem. Soc. Rev., 2020, 49, 3605–3637, 10.1039/C9CS00849G.
- N. Joseph, P. Ahmadiannamini, R. Hoogenboom and F. J. Ivo, Layer-by-layer preparation of polyelectrolyte multilayer membranes for separation, Polym. Chem., 2014, 5, 1817–1831, 10.1039/C3PY01262J.
- C. Wang, M. J. Park, H. Yu, H. Matsuyama, E. Drioli and H. K. Shon, Recent advances of nanocomposite membranes using layer-by-layer assembly, J. Membr. Sci., 2022, 661, 120926, DOI:10.1016/j.memsci.2022.120926.
- Z. Zhang, J. Zeng, J. Groll and M. Matsusaki, Layer-by-layer assembly methods and their biomedical applications, Biomater. Sci., 2022, 10, 4077–4094, 10.1039/D2BM00497F.
- B. C. Welch, O. M. McIntee, T. J. Myers, A. R. Greenberg, V. M. Bright and S. M. George, Molecular layer deposition for the fabrication of desalination membranes with tunable metrics, Desalination, 2021, 520, 115334, DOI:10.1016/j.desal.2021.115334.
- S. Chaudhury, E. Wormser, Y. Harari, E. Edri and O. Nir, Tuning the ion-selectivity of thin-film composite nanofiltration membranes by molecular layer deposition of alucone, ACS Appl. Mater. Interfaces, 2020, 12(47), 53356–53364, DOI:10.1021/acsami.0c16569.
- B. C. Welch, E. N. Antonio, T. P. Chaney, O. M. McIntee, J. Strzalka, V. M. Bright, A. R. Greenberg, T. Segal-Peretz, M. Toney and S. M. George, Building semipermeable films one monomer at a time: Structural advantages via molecular layer deposition vs interfacial polymerization, Chem. Mater., 2024, 36, 1362–1374, DOI:10.1021/acs.chemmater.3c02519.
- A. Tabernero, Á. González-Garcinuño, S. Cardea, I. De Marco and E. M. M. del Valle, PVDF-based membranes in biotechnology, Sep. Purif. Technol., 2025, 365, 132636, DOI:10.1016/j.seppur.2025.132636.
- C. Tushar, R. Ralish, M. Rajesh, M. Manikandan, R. Rajapandi, V. R. Kar and K. Jayakrishna, 8 - Maintenance and monitoring of composites, in Structural Health Monitoring of Biocomposites, Fibre- Reinforced Composites and Hybrid Composites, ed. M. Jawaid, M. Thariq and N. Saba, Woodhead Publishing, 2019, pp. 129–151 Search PubMed.
- S. Mohammadpourfazeli, S. Arash, A. Ansari, S. Yang, K. Mallick and R. Bagherzadeh, Future prospects and recent developments of polyvinylidene fluoride (PVDF) piezoelectric polymer; fabrication methods, structure, and electro-mechanical properties, RSC Adv., 2023, 13, 370–387, 10.1039/D2RA06774A.
- J. C. Barbosa, J. P. Dias, S. Lanceros-Méndez and C. M. Costa, Recent advances in poly(vinylidene fluoride) and its copolymers for lithium-ion battery separators, Membranes, 2018, 8, 45, DOI:10.3390/membranes8030045.
- C. M. Costa, V. F. Cardoso, P. Martins, D. M. Correia, R. Goncalves, P. Costa, V. Correia, C. Ribeiro, M. M. Fernandes, P. M. Martins and S. Lanceros-Méndez, Smart and multifunctional materials based on electroactive poly(vinylidene fluoride): Recent advances and opportunities in sensors, actuators, energy, environmental, and biomedical applications, Chem. Rev., 2023, 123, 11392–11487, DOI:10.1021/acs.chemrev.3c00196.
- J. Wang, L. Zheng, Z. Wu, Y. Zhang and X. Zhang, Fabrication of hydrophobic flat sheet and hollow fiber membranes from PVDF and PVDF-CTFE for membrane distillation, J. Membr. Sci., 2016, 497, 183–193, DOI:10.1016/j.memsci.2015.09.024.
- P. Peer, M. Janalikova, J. Sedlarikova, P. Pleva, P. Filip, J. Zelenkova and A. O. Siskova, Antibacterial filtration membranes based on PVDF-co-HFP nanofibers with the addition of medium-chain 1-monoacylglycerols, ACS Appl. Mater. Interfaces, 2021, 13, 41021–41033, DOI:10.1021/acsami.1c07257.
- A. Valverde, R. Fernandez-de Luis, H. Salazar, B. F. Gonçalves, S. King, L. Almásy, M. Kriechbaum, J. M. Laza, J. L. Vilas-Vilela, P. M. Martins, S. Lanceros-Mendez, J. M. Porro and V. I. Petrenko, On the multiscale structure and morphology of PVDF-HFP@MOF membranes in the scope of water remediation applications, Adv. Mater. Interfaces, 2023, 10, 2300424, DOI:10.1002/admi.202300424.
- R. E. Sousa, M. Kundu, A. Gören, M. M. Silva, L. Liu, C. M. Costa and S. L. Mendez, Poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) lithium-ion battery separator membranes prepared by phase inversion, RSC Adv., 2015, 5, 90428–90436, 10.1039/C5RA19335D.
- R. S. Pinto, J. P. Serra, J. C. Barbosa, M. M. Silva, M. Salado, A. F. Marijuan, E. Amayuelas, Y. Grosu, R. Gonçalves, S. Lanceros-Mendez and C. M. Costa, Tailoring poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) membrane microstructure for lithium-ion battery separator applications, J. Colloid Interface Sci., 2025, 680, 714–724, DOI:10.1016/j.jcis.2024.11.013.
- D. Chen and C. Pomalaza-Ráez, A self-cleaning piezoelectric PVDF membrane system for filtration of kaolin suspension, Sep. Purif. Technol., 2019, 215, 612–618, DOI:10.1016/j.seppur.2018.12.082.
- X. Guo, X. Tao, Y. Yang, S. Wang, J. Li and Y. Wu, Advances and application of PVDF-based composite membranes in flexible sensors, J. Electron. Mater., 2025, 54, 9393–9428, DOI:10.1007/s11664-025-12287-7.
- L. Lu, W. Ding, J. Liu and B. Yang, Flexible PVDF based piezoelectric nanogenerators, Nano Energy, 2020, 78, 105251, DOI:10.1016/j.nanoen.2020.105251.
- Y. Zhang, H. Zhang, L. Chen, J. Wang, J. Wang, J. Li, Y. Zhao, M. Zhang and H. Zhang, Piezoelectric polyvinylidene fluoride membranes with self-powered and electrified antifouling performance in pressure-driven ultrafiltration processes, Environ. Sci. Technol., 2022, 56, 16271–16280, DOI:10.1021/acs.est.2c05359.
- A. Siddique, H. Nawaz, S. Razzaque, A. Tabasum, H. Gong, H. Razzaq and M. Umar, PVDF-based piezo-catalytic membranes-A net-zero emission approach towards textile wastewater purification, Polymer, 2024, 16, 699, DOI:10.3390/polym16050699.
- Y. Chen, W. Wang, Y. Liang, C. Chen, R. Meng, L. Ba, Y. Wu, Y. Liu, W. Huang, F. Yang, J. Cheng and X. Yi, A method on the induction of piezoelectricity of PVDF by NaOH: Induced PVDF as ultrafiltration base membrane in interfacial polymerization to enhance the rejection of NaCl, Desalination, 2025, 609, 118896, DOI:10.1016/j.desal.2025.118896.
- J. Nunes-Pereira, S. Ribeiro, C. Ribeiro, C. J. Gombe, F. M. Gama, A. C. Gomes, D. A. Patterson and S. Lanceros-M'endez, Poly(vinylidene fluoride) and copolymers as porous membranes for tissue engineering applications, Polym. Test., 2015, 44, 234–241, DOI:10.1016/j.polymertesting.2015.05.001.
- H. Zhang, Q. Wang, J. Yin, Y. Gao, X. Zhang, Q. Zhou and Z. Cui, Evolution of piezoelectric PVDF membrane for energy transducer and membrane distillation, Chem. Eng. J., 2025, 169672, DOI:10.1016/j.cej.2025.169672.
- X. Zhong and Z. Guo, Piezoelectric PVDF membranes for emulsion separation with constant flux and high efficiency, Nanoscale Horiz., 2025, 10, 2123–2133, 10.1039/D5NH00298B.
- J. Xue, T. Wu, Y. Dai and Y. Xia, Electrospinning and electrospun nanofibers: methods, materials, and applications, Chem. Rev., 2019, 119, 5298–5415, DOI:10.1021/acs.chemrev.8b00593.
- F. Mokhtari, A. Samadi, A. O. Rashed, X. Li, J. M. Razal, L. Kong, R. J. Varley and S. Zhao, Recent progress in electrospun polyvinylidene fluoride (PVDF)-based nanofibers for sustainable energy and environmental applications, Prog. Mater. Sci., 2025, 148, 101376, DOI:10.1016/j.pmatsci.2024.101376.
- V. Nayak, J. M. Shivanna, S. Ramu, S. Radoor and R. G. Balakrishna, Efficacy of electrospun nanofiber membranes on fouling mitigation: A review, ACS Omega, 2022, 7, 43346–43363, DOI:10.1021/acsomega.2c02081.
- T. M. Subrahmanya, H. K. Makari, A. B. Arshad, P. T. Lin, J. Widakdo, H. F. M. Austria, C.-C. Hu, J.-Y. Lai and W.-S. Hung, A review of recent progress in polymeric electrospun nanofiber membranes in addressing safe water global issues, RSC Adv., 2021, 11, 9638–9663, 10.1039/d1ra00060h.
- X. Wang and B. S. Hsiao, Electrospun nanofiber membranes, Curr. Opin. Chem. Eng., 2016, 12, 62–81, DOI:10.1016/j.coche.2016.03.001.
- B. Yan, Y. Zhang, Z. Li, P. Zhou and Y. Mao, Electrospun nanofibrous membrane for biomedical application, SN Appl. Sci., 2022, 4, 172, DOI:10.1007/s42452-022-05056-2.
- X. Li, R. Zhou, Z. Wang, M. Zhang and T. He, Electrospun metal-organic framework based nanofibers for energy storage and environmental applications: Current approaches and challenges, J. Mater. Chem. A, 2022, 10, 1642–1681, 10.1039/D1TA08413E.
- H. I. Adil, M. R. Thalji, S. A. Yasin, I. A. Saeed, M. A. Assiri, K. F. Chong and G. A. M. Ali, Metal-organic frameworks (MOFs) based nanofiber architectures for the removal of heavy metal ions, RSC Adv., 2022, 12, 1433–1450, 10.1039/d1ra07034g.
- P. Lin, X. Lu, B. J. Deka, J. Shang, H. Wu, J. Sun, C. Yi, M. U. Farid, A. K. An and J. Guo, Research progress in the preparation of electrospinning MOF nanofiber membranes and applications in the field of photocatalysis, Sep. Purif. Technol., 2025, 356, 129948, DOI:10.1016/j.seppur.2024.129948.
- M. H. Hashem, M. Wehbe, P. Damacet, R. K. El Habbal, N. Ghaddar, K. Ghali, M. N. Ahmad, P. Karam and M. Hmadeh, Electrospun metal-organic framework-fabric nanocomposites as efficient bactericides, Langmuir, 2023, 39, 9503–9513, DOI:10.1021/acs.langmuir.3c01039.
- B. Wu, J. Pan, L. Ge, H. Wang and T. Xu, Oriented MOF-polymer composite nanofiber membranes for high proton conductivity at high temperature and anhydrous condition, Sci. Rep., 2014, 4, 4334, DOI:10.1038/srep04334.
- X. Li, S. Wang, M. Zheng, Z. Ma, Y. Chen, L. Deng, W. Xu, G. Fan, S. Khademolqorani, S. N. Banitaba and A. I. Osman, Synergistic integration of MXene nanostructures into electrospun fibers for advanced biomedical engineering applications, Nanoscale Horiz., 2024, 9, 1703–1724, 10.1039/d4nh00209a.
- B. Pant, M. Park and A. A. Kim, MXene-embedded electrospun polymeric nanofibers for biomedical applications: Recent advances, Micromachines, 2023, 14, 1477, DOI:10.3390/mi14071477.
- F. Mokhtari, R. W. Symes, Ž. Simon, B. Dharmasiri, L. C. Henderson, M. W. Joosten and R. J. Varley, An energy efficient and sustainable approach to structural health monitoring in carbon fiber composites: harnessing sound-induced vibration with Ti3C2Tx MXene/AgNPs modified P(VDF-TrFE) sensors, J. Mater. Chem. A, 2025, 13, 6482–6492, 10.1039/D4TA07797K.
- A. Barjola, O. Sahuquillo, Á. Sonseca, V. Compañ and E. Giménez, Flexible piezoelectric nanogenerator based on Ti3C2Tx-coated electrospun PVDF–TrFE nanofibers, J. Mater. Chem. C, 2025, 13, 15451–15460, 10.1039/D5TC01005E.
- S. Khademolqorani, S. N. Banitaba, A. Gupta, N. Poursharifi, A. A. Ghaffari, V. V. Jadhav, W. U. Arifeen, M. Singh, M. Borah, E. Chamanehpour and Y. K. Mishra, Application scopes of miniaturized MXene-functionalized electrospun nanofibers-based electrochemical energy devices, Small, 2024, 20, 2309572, DOI:10.1002/smll.202309572.
- A. S. Levitt, M. Alhabeb, C. B. Hatter, A. Sarycheva, G. Dion and Y. Gogotsi, Electrospun MXene/carbon nanofibers as supercapacitor electrodes, J. Mater. Chem. A, 2019, 7, 269–277, 10.1039/C8TA09810G.
- K. M. Dobosz, C. A. Kuo-Leblanc, T. J. Martin and J. D. Schiffman, Ultrafiltration membranes enhanced with electrospun nanofibers exhibit improved flux and fouling resistance, Ind. Eng. Chem. Res., 2017, 56, 5724–5733, DOI:10.1021/acs.iecr.7b00631.
- K. M. Dobosz, C. A. Kuo-Leblanc, M. E. Bowden and J. D. Schiffman, Robust, small diameter hydrophilic nanofibers improve the flux of ultrafiltration membranes, Ind. Eng. Chem. Res., 2021, 60, 9179–9188, DOI:10.1021/acs.iecr.1c01332.
- F. Montero-Rocca, J. D. Badia-Valiente, R. Jiménez-Robles, V. Martínez-Soria and M. Izquierdo, PVDF nanofiber membranes for dissolved methane recovery from water prepared by combining electrospinning and hot-pressing methods, ACS Polym. Au, 2025, 5, 353–368, DOI:10.1021/acspolymersau.5c00021.
- G. Hong, L. Shen, M. Wang, Y. Yang, X. Wang, M. Zhu and B. S. Hsiao, Nanofibrous polydopamine complex membranes for adsorption of Lanthanum (III) ions, Chem. Eng. J., 2014, 244, 307–316, DOI:10.1016/j.cej.2014.01.073.
- L. Kravets, I. Vinogradov, A. Rossouw, B. Gorberg, A. Nechaev and P. Apel, Functionalization of PET track-etched membranes with electrospun PVDF nanofibers for hybrid membranes fabrication in water desalination, Sep. Purif. Technol., 2025, 371, 133395, DOI:10.1016/j.seppur.2025.133395.
- A. A. Ali, A. Al-Othman, M. Tawalbeh, A. Ali, C. A. Quist-Jensen and M. M. A. Shirazi, Membrane technologies for sustainable development goals: A critical review of bright horizons, J. Environ. Chem. Eng., 2025, 13, 114998, DOI:10.1016/j.jece.2024.114998.
- N. Rabiee, R. Sharma, S. Foorginezhad, M. Jouyandeh, M. Asadnia, M. Rabiee, O. Akhavan, E. C. Lima, K. Formela, M. Ashrafizadeh, Z. Fallah, M. Hassanpour, A. Mohammadi and M. R. Saeb, Green and Sustainable Membranes: A review, Environ. Res., 2023, 231(2), 116133, DOI:10.1016/j.envres.2023.116133.
- G. Szekely, The 12 principles of green membrane materials ad processes for realizing the United Nations' sustainable development goals, RSC Sustainability, 2024, 2, 871–880, 10.1039/d4su00027g.
- N. K. Khanzada, R. A. Al-Juboori, M. Khatri, F. E. Ahmed, Y. Ibrahim and N. Hilal, Sustainability in membrane technology: Membrane recycling and fabrication using recycled waste, Membranes, 2024, 14, 52, DOI:10.3390/membranes14020052.
| This journal is © The Royal Society of Chemistry 2026 |