Comb-shaped amphiphilic triblock copolymers blend PVDF membranes overcome the permeability-selectivity trade-off for protein separation

Abstract

In order to reduce membrane fouling and fabricate highly selective membranes with high water permeability, three kinds of comb-shaped amphiphilic triblock copolymers, poly[poly(ethylene glycol) methacrylate]-b-poly(methyl methacrylate)-b-poly[poly(ethylene glycol) methacrylate] (PPEGMA-b-PMMA-b-PPEGMA, named as PEME), were synthesized via RAFT polymerization and used as modifiers to prepare poly(vinylidene fluoride) (PVDF) blend membranes by the non-solvent induced phase separation (NIPS) method. The effects of PEME with different hydrophilic PPEGMA length on the surface chemical structure, morphology, permeability and antifouling properties of the blend membranes were investigated detailedly. The results from ATR-FTIR and XPS tests confirmed that hydrophilic PPEGMA segments in PEME were enriched on the membrane surface due to PEME induced surface segregation. With the increase of the hydrophilic chain length in PEME, the mean pore size, porosity and roughness of the blend membrane increased gradually, indicating the modifier had the ability to adjust the membrane pore structure. Compared with pure membrane, the hydrophilicity of blend membranes was enhanced and the protein adsorption of representative bovine serum albumin (BSA) decreased obviously. After three cycles of the water-BSA-water, the M-2 blend membrane exhibited high BSA solution flux (150 L·m−2·h−1), excellent rejection (up to 99.99%) and satisfactory antifouling performance. In addition, compared with the recently published PVDF blend ultrafiltration membranes prepared by NIPS method, the M-2 membrane with surface small pore size, high flux, high selectivity and low fouling properties overcame the permeability-selectivity trade-off for BSA solution separation and showed a good application prospect for efficiently protein separation.