Photografted temperature-sensitive poly(N-isopropylacrylamide) thin film with a superfast response rate and an interesting transparent–opaque–transparent change in its deswelling process

Abstract

Fast swelling/deswelling rates with a change of temperature are required for the application of poly(N-isopropylacrylamide) (PNIPAAm)-based materials. This article reports the fabrication of temperature-sensitive PNIPAAm thin films by a UV-induced surface photografting method. The grafted PNIPAAm thin films have high swelling ratios (10–60) and superfast swelling and response rates (<10 s). A fast development and decay of turbidity in the grafted PNIPAAm gel layers at a temperature above the lower critical solution temperature (LCST) is also reported. The excellent swelling and response properties of the PNIPAAm thin films are believed to be due to the small thickness of the grafted layers, the long but less crosslinked polymer chains and their uneven distribution.