Surface modification of ethylene-vinyl acetate membrane grafted with poly(N-isopropylacrylamide) by UV-irradiation

Surface modification of ethylene-vinyl acetate membrane by grafting poly(N-isopropylacrylamide) was initiated under UV-irradiation. Besides benzophenone and ammonium persulfate were used as initiators, which could enhance the yield of grafting markedly. The occurrence of grafting polymerization of N-isopropylacrylamide was testified by the attenuated total multiple reflection technique and X-ray photoelectron spectroscopy. Scanning electron micrograph showed that the surface morphology of ethylene-vinyl acetate membrane changed after modification. The lower critical solution temperature of the membrane was determined by differential scanning calorimetry. The wettability of membrane was investigated by water contact angle measurement. The results showed that the grafting degree increased with irradiation time, monomer and ammonium persulfate concentration at the beginning of reaction. It was also found that the modified membrane surface became hydrophilic and displayed thermosensitivity similar to that of poly(N-isopropylacrylamide) gel, and the lower critical solution temperature was about 32°C.