Robust Stimuli-Responsive Membranes Prepared from a Blend of Polysulfone and a Graft Copolymer Bearing Binary Side Chains with Thermo- and pH-Responsive Switching Behavior

Graphical Doubly responsive : A thermo- and pH-sensitive binary graft copolymer bearing anchoring side chains was synthesized and blended with commercial polysulfone to prepare thermo- and pH-responsive blended membranes, which exhibited robust, reversible, independent temperature- and pH-responsive water wettability and water permeability (see figure). A stimuli-responsive membrane exhibiting independent pH- and temperature-responsive behavior was fabricated from a blend of commercial polysulfone with a functional amphiphilic binary graft copolymer, namely, polysulfone- graft -(poly(isopropylacrylamide- co -acrylic acid)- random -poly(methyl acrylate)), denoted PSf- g -(P(NIPAAm- co -AA)- r -PMMA). Two graft copolymers with different lengths of P(NIPAAm- co -AA) side chains were designed and enriched on the membrane surface to serve as thermo- and pH-responsive on/off switches. The differences between the dual-responsive behaviors of the two kinds of polymer-blend membranes were studied by water-flux and contact-angle measurements. The PMMA side chains served to securely anchor the graft copolymers to the membrane substrate, and the blended membrane prepared from binary graft copolymer was more stable and exhibited more robust stimuli-responsive behavior than that prepared from mono-graft copolymer PSf- g -P(NIPAAm- co -AA).