Journal of Colloid and Interface Science, Vol.531, 585-592, 2018
Dual stimuli-responsive polysulfone membranes with interconnected networks by a vapor-liquid induced phase separation strategy
Dual pH- and thermo-responsive polysulfone (PSf) membranes with three-dimensionally interconnected networks are fabricated by introducing poly(acrylic acid-co-N-isopropylacrylamide) (P(AA-NIPAm)) into the membrane surfaces and pore walls during membrane formation via a vapor-liquid induced phase separation (V-LIPS) process. After introducing the copolymers of P(AA-NIPAm), the fabricated membranes exhibit impressive open network pores on the surfaces, meanwhile their cross-sectional structure turns from classical asymmetric finger-like structure into bi-continuous nanopores throughout the whole thickness of membrane, due to high solution viscosity and low mass transfer rate of VIPS process. Furthermore, pure water permeation tests show that the pure water permeation (L-p) and the molecular weight cutoff (MWCO) of the fabricated PSf/P(AA-NIPAm) membranes increases sharply as the solution pH decreases from 12.5 to 1.5 and the feed temperature increases from 25 to 50 degrees C, attributing to the increasing pore size. With the decreasing mass ratio of AA to NIPAm, the pH-responsive coefficient decreases, while the temperature- responsive coefficient increases. In particular, for the fabricated membrane with the mass ratio of AA to NIPAm of 3 to 2, L-p changes from similar to 16.0 to similar to 821.4 L M-2 h(-1) bar(-1) and MWCO increases from similar to 223.1 to similar to 1493.2 kDa, as the filtration experiments are operated with feed pH and temperature of 12.5/25 degrees C and 1.5/50 degrees C respectively. The results proposed in this study provide a novel mode for design and development dual responsive porous membranes in situ, which will enable good separation of various materials and expand the scope of membrane applications. (C) 2018 Elsevier Inc. All rights reserved.
Keywords:Polysulfone membranes;Gating membranes;Dual thermo- and pH-response;In situ cross-linking polymerization;Phase separation