Fabrication of hydrophilic PVDF ultrafiltration membranes via thermally induced phase separation coupled with amphiphilic copolymer deposition

Abstract

In this work, we propose a facile one-step method to fabricate poly(vinylidene fluoride) (PVDF) ultrafiltration hollow fiber membranes through coupled thermally induced phase separation (TIPS) and deposition of amphiphilic copolymer poly(styrene-co-maleic anhydride) (PSMA). A thorough examination of how the addition of PSMA influenced the membrane formation and performance was conducted. The mechanism behind the synergistic effect between TIPS process and deposition of PSMA on the membrane surface was discussed in detail. The difference in the phase separation behavior of PVDF and PSMA during membrane preparation caused the deposition of PSMA forming a hydrophilic layer on the PVDF porous structure without altering the membrane bulk structure. The enrichment of PSMA in membrane outer surface not only improved the hydrophilicity of the membrane, but also effectively reduced the membrane pore size, while maintaining the overall bulk porosity. PSMA deposition resulted in enhanced pure water flux and BSA rejection, effectively overcoming the traditional trade-off between permeability and selectivity. This straightforward approach of blending suitable amphiphilic copolymers into the polymer solution exhibited significant potential for the rapid and large-scale preparation of hydrophilic PVDF-based ultrafiltration membranes in the TIPS process.