Thermo-responsive gating characteristics of poly (N-isopropylacrylamide)-grafted membranes

Both hydrophilic Nylon-6 membranes and hydrophobic poly(vinylidene fluoride) (PVDF) membranes, with a wide range of grafting yields of poly(N-isopropylacrylamide) (PNIPAM), were prepared using the plasma-graft pore-filling polymerization method. The effect of the physical and chemical properties of the substrates on the thermo-responsive gating characteristics of the PNIPAM-grafted membranes was investigated experimentally. For both the PVDF and Nylon-6 membranes, the grafted PNIPAM polymers were found not only on the membranes outer surface, but also on the inner surfaces of the pores throughout the entire thickness of the membrane. The thermo-responsive gating characteristics of the PNIPAM-grafted membranes were heavily affected by the physical and chemical properties of the porous membrane substrates. The PNIPANI-g-Nylon-6 membranes exhibited a much larger thermo-responsive gating coefficient than the PNIPAM-g-PVDF membranes. Furthermore, to achieve the largest thermo-responsive gating coefficient. the corresponding optimum grafting yield of PNIPAM for the PNIPAM-g-Nylon-6 membranes was also larger than that for the PNIPAM-g-PVDF membranes.