Surprising transformation of a block copolymer into a high performance polystyrene ultrafiltration membrane with a hierarchically organized pore structure
KAUST DepartmentPhysical Sciences and Engineering (PSE) Division
Chemical and Biological Engineering Program
Advanced Membranes and Porous Materials Research Center
Imaging and Characterization Core Lab
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AbstractWe describe the preparation of hierarchical polystyrene nanoporous membranes with a very narrow pore size distribution and an extremely high porosity. The nanoporous structure is formed as a result of unusual degradation of the poly(4-vinyl pyridine) block from self-assembled poly(styrene)-b-poly(4-vinyl pyridine) (PS-b-P4VP) membranes through the formation of an unstable pyridinium intermediate in an alkaline medium. During this process, the confined swelling and controlled degradation produced a tunable pore size. We unequivocally confirmed the successful elimination of the P4VP block from a PS-b-P4VPVP membrane using 1D/2D NMR spectroscopy and other characterization techniques. Surprisingly, the long range ordered surface porosity was preserved even after degradation of the P4VP block from the main chain of the diblock copolymer, as revealed by SEM. Aside from a drastically improved water flux (∼67% increase) compared to the PS-b-P4VP membrane, the hydraulic permeability measurements validated pH independent behaviour of the isoporous PS membrane over a wide pH range from 3 to 10. The effect of the pore size on protein transport rate and selectivity (a) was investigated for lysozyme (Lys), bovine serum albumin (BSA) and globulin-γ (IgG). A high selectivity of 42 (Lys/IgG) and 30 (BSA/IgG) was attained, making the membranes attractive for size selective separation of biomolecules from their synthetic model mixture solutions.
CitationShevate R, Kumar M, Karunakaran M, Canlas C, Peinemann K-V (2018) Surprising transformation of a block copolymer into a high performance polystyrene ultrafiltration membrane with a hierarchically organized pore structure. Journal of Materials Chemistry A. Available: http://dx.doi.org/10.1039/c7ta09777h.
SponsorsThe research reported in this manuscript was supported by King Abdullah University of Science and Technology (KAUST), Thuwal, Kingdom of Saudi Arabia under baseline funding. R. S. thanks Dr Sayali Shaligram and Dr Tiefan Huang for assistance in NMR data analysis and optical imaging. Fig. 4(c) and Table of content was created by Ivan Gromicho, scientific illustrator at King Abdullah University of Science and Technology (KAUST).
PublisherRoyal Society of Chemistry (RSC)
JournalJournal of Materials Chemistry A