Jump to main content
Jump to site search

Issue 9, 2019
Previous Article Next Article

Zwitterionic copolymer additive architecture affects membrane performance: fouling resistance and surface rearrangement in saline solutions

Author affiliations

Abstract

Membrane separations are simple to operate, scalable, versatile, and energy efficient, but their broader use is curtailed by fouling or performance decline due to feed component depositing on the membrane surface. Surface functionalization with groups such as zwitterions can mitigate the adsorption of organic compounds, thus limiting fouling. This can be achieved by using surface-segregating copolymer additives during membrane manufacture, but there is a need for better understanding of how the polymer structure and architecture affect the effectiveness of these additives in improving membrane performance. In this study, we aim to explore the impact of the architecture of zwitterionic copolymer additives for polyvinylidene fluoride (PVDF)-based membranes in fouling mitigation and ionic strength response. We prepared membranes from blends of PVDF with zwitterionic (ZI) copolymers with two different architectures, random and comb-shaped. As the random copolymer, we used poly(methyl methacrylate-random-sulfobetaine-2-vinyl pyridine) (PMMA-r-SB2VP) synthesized by free radical polymerization. The comb-shaped copolymer was synthesized by grafting SB2VP side-chains from a PVDF backbone by controlled radical polymerization. Membranes were fabricated from PVDF-copolymer blends containing up to 5 wt% ZI copolymer. Compared to the additive-free PVDF membrane, water permeance increased five-fold with 5 wt% addition of either copolymer. The comb copolymer additive led to better resistance to fouling by a saline oil-in-water emulsion and to simulated protein adsorption in Atomic Force Microscopy (AFM) force measurements. The additive architecture had a significant influence on how membranes respond to changes in feed salinity, which is known to affect intra- and inter-molecular interactions in zwitterionic polymers. The random copolymer containing membrane showed a small and mostly reversible decrease in its permeance with salinity. In contrast, the comb copolymer-containing membrane underwent a conformational reorganization in saline solutions that leads to an irreversible permeance decrease, increased zwitterionic group content on the membrane surface, and smoother surface topography. The higher mobility of the zwitterionic groups in the comb-shaped architecture facilitates reorganization of the zwitterionic side-chains in response to ionic strength. Overall, this study establishes a new approach for developing highly fouling resistant membranes and defines how the architecture of a zwitterionic copolymer additive impacts the ionic strength response and fouling resistance of the membrane.

Graphical abstract: Zwitterionic copolymer additive architecture affects membrane performance: fouling resistance and surface rearrangement in saline solutions

Back to tab navigation

Supplementary files

Publication details

The article was received on 30 Nov 2018, accepted on 25 Jan 2019 and first published on 25 Jan 2019


Article type: Paper
DOI: 10.1039/C8TA11553B
Citation: J. Mater. Chem. A, 2019,7, 4829-4846

  •   Request permissions

    Zwitterionic copolymer additive architecture affects membrane performance: fouling resistance and surface rearrangement in saline solutions

    P. Kaner, A. V. Dudchenko, M. S. Mauter and A. Asatekin, J. Mater. Chem. A, 2019, 7, 4829
    DOI: 10.1039/C8TA11553B

Search articles by author

Spotlight

Advertisements