Poly(N-isopropylacrylamide) (PNIPAM) was successfully grafted on the surfaces and in the pores of polycarbonate track-etched (PCTE) membranes by the plasma-graft pore-filling polymerization method

and the chemical composition

microstructure and thermo-responsive characteristics of the PNIPAM-g-PCTE membrane were investigated systematically with XPS

SEM

FT-IR

AFM

contact angle instrument and water flux experiments.The objective of this study was to obtain some guidance for the design and preparation of environmental stimuli-responsive gating membranes. The results showed that

PNIPAM was homogeneously grafted on the surface and in the pores of PCTE membranes.When pore-filling ratio was smaller than 44.2%

the pores of PNIPAM-g-PCTE membranes showed thermo-responsive gating characteristics because of the conformational change of grafted PNIPAM in the pores

and the pore diameters of PNIPAM-grafted membranes became smaller with increasing the pore-filling ratio. On the other hand

when the pore-filling ratio was larger than 44.2%

the pores of membranes immersed in water were choked by the volume expansion of the grafted PNIPAM polymers

and the membranes did not show thermo-responsive gating characteristics any more. The critical pore-filling ratio for choking the membrane pores was in the range from 30% to 40% at 40 ℃. The contact angle of PNIPAM-g-PCTE membrane increased from 58.5° to 87.9° when the temperature changed from 25 ℃ to 40 ℃. The thermo-responsive gating characteristics of the water flux of PNIPAM-g-PCTE membranes were mainly dependent on the pore size change rather than the variation of membrane/pore surface hydrophilicity.