Introduction to Pioneering Investigators 2023
Holger
Frey
a and
Emily
Pentzer
b
aJohannes Gutenberg University Mainz, Germany. E-mail: hfrey@uni-mainz.de
bTexas A&M University, College Station, USA. E-mail: emilypentzer@tamu.edu
Mid-career researchers have already established a platform of scientific independence and output, and they may choose to build upon these successes or pivot their research programs into new directions. Regardless, these researchers tend to have more freedom and momentum, as early career jitters have been calmed, multiple papers published and grants awarded, and junior researchers trained.
In the area of sustainable polymer production, Wu and coworkers compared the synthesis of poly(ethylene succinate) by ring-opening copolymerization and polycondensation, taking into account monomer preprocessing, polymerization conditions, post-processing, and total cost (https://doi.org/10.1039/D3PY01314F). Complementary to this, Thickett and coworkers reported the synthesis of a block copolymer (PNIPAM-b-PCL) in air by simultaneous anionic and radical polymerizations, harnessing a polymerizable deep eutectic solvent rather than traditional solvents (https://doi.org/10.1039/D3PY00294B). Towards the scalable synthesis of conjugated polymers, Asha S. K. and coworkers reported the combination of direct heteroarylation polymerization and recyclable heterogeneous catalysts, demonstrating catalyst recyclability up to five times and applicability to various monomers (https://doi.org/10.1039/D3PY00183K).
In the area of new polymerization strategies, Zhang and coworkers reported the metal-free polymerization of indoles and hydrosilanes through regioselective dehydrogenation silylation of indoles to produce linear and hyperbranched poly(silyl indole)s that are highly luminescent (https://doi.org/10.1039/D2PY01470J). Furthermore, Kalow and coworkers demonstrated that photoredox Diels–Alder reactions can be used to produce novel sp3-rich ladder polymers (https://doi.org/10.1039/D3PY00833A). Chen and coworkers integrated new xanthene-modified 1,2-dioxetane derivatives into polymer chains and networks; these mechano-chemiluminescent chromophores endowed bright chemiluminescence, when the bulk polymer samples were stretched (https://doi.org/10.1039/D3PY00786C).
Polymer synthesis also strongly benefits from advances in catalysts and initiators, as seen in a handful of reports in this themed issue. For example, Hong and coworkers reported Lewis-pair catalysts for controlled polymerization of typically inert biomass-derived acrylic monomers. The authors found that a frustrated Lewis pair serves as an efficient mediator of polymerization and can be used to produce novel polymer backbones with enhanced thermal stability (https://doi.org/10.1039/D3PY00546A). Magenau and coworkers reported the impact of carboxylic acid deblockers on alkyl-borane initiated RAFT, finding that lower pKa acids can be used at lower concentrations without a loss of control (https://doi.org/10.1039/D3PY00348E). Perhaps in a smellier direction, Jenkins and coworkers reported the use of commercial garlic essential oil as monomer, initiator, and solvent for the synthesis of polysulfides, evaluating their application as adhesives (https://doi.org/10.1039/D3PY00390F). In applications toward vat 3D printing and additive manufacturing, Ortyl and coworkers reported a new group of cationic photoinitiators based on push–pull coumarin-based iodonium salts, highlighting their photothermal initiating activity and application to the production of nanocomposites (https://doi.org/10.1039/D3PY00359K).
Post-polymerization modification is another important route to tailoring the chemistry of polymers. In this collection, Klausen and coworkers reported the oxidative transformation of block copolymers containing aromatic organoborane repeat units to –OH units, giving access to PS-b-PVA block copolymers that are difficult to access by controlled radical polymerization of vinyl acetate (https://doi.org/10.1039/D3PY00706E). Complementary to this, Wilson and coworkers reported the use of electrochemistry to induce a Hofmann rearrangement, transforming a primary amide of polyacrylamide to an isocyanate, which then reacts with an alcohol solvent to give an O-alkyl carbamate, paving the way to new polymer compositions (https://doi.org/10.1039/D3PY00594A).
Polymer chemistry continues to significantly impact the field of manufacturing, especially in additive manufacturing and 3D printing. Van Vlierberghe and coworkers advanced the digital light projection (DLP) manufacturing of polyesters by reporting how polymer network architecture of thiol–ene photocrosslinked PCL can be used to tune the physical characteristics of printed parts (https://doi.org/10.1039/D3PY00381G). Complementary to this, Smaldone and coworkers endowed self-healing and reprocessability to a bio-based aromatic resin printed by DLP; the authors also highlighted that the chemistry of the system enabled an impressive increase in the Young's modulus by simply heating the printed parts (https://doi.org/10.1039/D3PY00200D). In contrast, Ke and coworkers reported the direct-ink-write printing of polypseudorotaxanes bearing ketoenamine-based dynamic covalent cross-links; the authors used irreversible enol–keto tautomerization to impart good chemical stability (https://doi.org/10.1039/D3PY00337J). Complementary to this, Schlögl et al. leveraged a photolatent transesterification catalyst in printed vitrimers to realize spatially resolved catalyst activation; critically, the authors designed the photoinitiator for curing to be wavelength-orthogonal to that used for bond exchange, thereby enabling reshaping of the printed parts (https://doi.org/10.1039/D3PY00377A).
Polymer chemistry also plays a pivotal role in self-assembly and templating different structures and properties. For example, Lee and coworkers used crystallization-driven self-assembly to prepare well-aligned domains of n-type nanowires and p-type polymers in non-halogenated solvents; electron microtomography confirmed the impressive long-range alignment and high degree of interface (https://doi.org/10.1039/D3PY00718A). In contrast, Kempe and coworkers reported the first example of rod-like length-controlled polymer nanoparticles prepared by the heat-induced crystallization-driven self-assembly (CDSA) of poly(2-oxazines); the authors developed a method to identify seeded versus spontaneous growth via1H NMR and evaluated bio-nano interactions (https://doi.org/10.1039/D3PY00399J). Mosquera and coworkers produced a fully biobased polylimonene oxide and used this as an additive to PLA for melt processing, resulting in modulated thermal properties as well as increased flexibility, which is attributed to the miscibility of the two polymers (https://doi.org/10.1039/D3PY00667K).
In tailoring polymer interactions, Hudson and coworkers reported copolymers with through-space, thermally activated donor–acceptor pairs with blue-green fluorescence in solution and the solid state, complementing the polymer synthesis with DFT calculations (https://doi.org/10.1039/D3PY00325F). Schmidt and coworkers demonstrated that the thermally responsive polymer, poly(N,N-diethyl acrylamide), prepared by RAFT had a significant shift in cloud point when part of an aqueous two-phase system compared to a pure aqueous solution, relevant to the production of multicompartment hydrogels (https://doi.org/10.1039/D3PY00734K). Tan and coworkers coupled heterogeneous RAFT with polymerization-induced self-assembly, transitioning from emulsion to dispersion polymerization by solvent control; this work expands the scope of block copolymers and morphologies accessible via this method (https://doi.org/10.1039/D3PY01006F). Lastly, Müllner and coworkers prepared polymer brush-grafted cellulose nanocrystals via SI-ATRP, then loaded them with titanium precursors via ionic interactions; pyrolysis gave high specific surface area mesoporous carbon-coated TiO2 nanotubes with application potential in lithium-ion batteries (https://doi.org/10.1039/D3PY00194F).
The number of excellent contributions to this themed issue highlights the continued impact that polymer chemistry has in cross-disciplinary fields, which will undoubtedly be supported by recent developments in artificial intelligence. For example, Ballard and coworkers describe the use of an artificial neural network model capable of predicting reactivity ratios based solely on monomer chemical structures, enabling the prediction of reactivity ratios for monomer pairs for which no kinetic data is available (https://doi.org/10.1039/D3PY00246B). Thus, in addition to the established areas of making new polymer backbones, catalysis, and self-assembly, editing of polymer backbones and the polymer chemistry of additive manufacturing continue to rapidly evolve. Taken together, these articles highlight the strength of the polymer chemistry community and its wide-reaching impact in both fundamental and applied research.
Holger Frey, Polymer Chemistry Associate Editor
Contributing authors:
Dr Yuetao Zhang, Jilin University College of Chemistry, China
Synthesis of fluorescent poly(silyl indole)s via borane-catalyzed C–H silylation of indoles
Dr Asha S. K., CSIR-National Chemical Laboratory, India
Exploring SiliaCat Pd-DPP as a recyclable heterogeneous catalyst for the multi-batch direct heteroarylation polymerization for P(NDI2OD-T2).
Dr Markus Müllner, The University of Sydney, Australia
Polymer brush-grafted cellulose nanocrystals for the synthesis of porous carbon-coated titania nanocomposites
Dr Ronald A. Smaldone, University of Texas at Dallas, United States
Thermal annealing effects on the mechanical properties of bio-based 3D printed thermosets
Dr Nicholas Ballard, University of the Basque Country, Spain
An artificial neural network to predict reactivity ratios in radical copolymerization
Dr Stuart C. Thickett, University of Tasmania, Australia
Solvent-free, photoinduced block copolymer synthesis from polymerizable eutectics by simultaneous PET-RAFT and ring-opening polymerization in air
Dr Zachary M. Hudson, The University of British Columbia, Canada
Through-space charge transfer delayed fluorescence in tris(triazolo)triazine donor–acceptor copolymers
Dr Chenfeng Ke, Dartmouth College, United States
3D-printed ketoenamine crosslinked polyrotaxane hydrogels and their mechanochromic responsiveness
Dr Andrew J. D. Magenau, Drexel University, United States
Alkylborane initiated RAFT polymerization: impact of carboxylic acid deblockers
Professor Joanna Ortyl, Cracow University of Technology, Poland
Push–pull coumarin-based one-component iodonium photoinitiators for cationic nanocomposite 3D-VAT printing
Dr Sandra Schlögl, Polymer Competence Center Leoben GmbH, Austria
Spatially resolved photoactivation of dynamic exchange reactions in 3D-printed thiol–ene vitrimers
Dr Sandra Van Vlierberghe, Ghent University, Belgium
Exploiting the network architecture of thiol–ene photo-crosslinked poly(ε-caprolactone) towards tailorable materials for light-based 3D-printing
Dr Courtney L. Jenkins, Idaho State University, United States
Allyl sulfides in garlic oil initiate the formation of renewable adhesives
Dr Kristian Kempe, Monash University, Australia
Length-tuneable biocompatible block copolymer nanorods with a poly(2-methyl-2-oxazine)-corona via heat-induced crystallisation-driven self-assembly
Professor Shouchun Yin, Hangzhou Normal University, China
Appropriate introduction of nitrile groups to balance NIR-II fluorescence imaging with photothermal therapy/photoacoustic imaging
Dr Hong Miao, University of Chinese Academy of Sciences, China
Insights into the interaction between bis(aryloxide)alkylaluminum and N-heterocyclic carbene: from an abnormal Lewis adduct to a frustrated Lewis pair for efficient polymerizations of biomass-derived acrylic monomers
Dr Paul Wilson, University of Warwick, United Kingdom
An electrochemical Hofmann rearrangement on acrylamide copolymers
Dr Marta E. G. Mosquera, University of Alcala, Spain
Insight into the melt-processed polylimonene oxide/polylactic acid blends
Dr Rebekka S. Klausen, Johns Hopkins University, United States
RAFT polymerization of an aromatic organoborane for block copolymer synthesis
Dr Eunji Lee, Gwangju Institute of Science and Technology, Republic of Korea
Efficient all polymer active layers with long-range ordered 1D p–n nanoheterojunctions confirmed by TEM tomography
Dr Bernhard V. K. J. Schmidt, University of Glasgow, United Kingdom
Thermoresponsive behaviour of poly(N,N-diethylacrylamide) in aqueous two-phase systems
Dr Yulan Chen, Jilin University and Tianjin University, China
Mechanically induced chemiluminescence of xanthene-modified 1,2-dioxetane in polymers
Professor Julia A. Kalow, Northwestern University, United States
Photoredox Diels–Alder ladder polymerization
Professor Jianbo Tan, Guangdong University of Technology, China
From RAFT emulsion polymerization to RAFT dispersion polymerization: a facile approach to tuning dispersities and behaviors of self-assembled block copolymers
Dr Guang-Peng Wu, Zhejiang University, China
A direct comparison between ring-opening copolymerization and polycondensation to produce polyesters using poly(ethylene succinate) as an example
Dr Jennifer Anne Garden, University of Edinburgh, United Kingdom
Exploiting controlled transesterification as a “top down” approach to tailor poly(ε-caprolactone)-poly(lactic acid) copolymer structures with bis-Zn catalysts
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