Thermally On-Off Switching Membranes Prepared by Pore-Filling Poly(N-isopropylacrylamide) Hydrogels

Pore-filling N-isopropylacrylamide (NIPAAM) polymer hydrogels were successfully grafted onto track-etched polycarbonate (PC) membranes by plasma-induced graft copolymerization. The microstructure and morphology of the PC-g-PNIPAAM membranes were investigated by XPS, SEM, ATR-FTIR, TGA, and water flux experiments. The effective pore sizes were regulated by the volume change of the cross-linked PNIPAAM hydrogels in the temperature range around its lower critical solution temperature (LCST). The PC-g-PNIPAAM membranes demonstrated a fast and reversible valve switching mechanism in a small temperature range. The on-off water flux ratio became more significant with the increase of the monomer concentration. Contact angle results showed that the thermal-responsive gating characteristics of PC-g-PNIPAAM membranes were mainly dependent on the pore size change.