Preparation of PNIPAM-Azo by RAFT polymerization and their application in thermo- and light-responsive hydrogel

Thermo-responsive poly(N-isopropylacrylamide) with terminal azobenzene group (PNIPAM-Azo) can show distinct property changes in response to temperature and light. In this paper, azobenzene-terminated trithiocarbonate (DDMAT-Azo) was synthesized as chain transfer agent, with which PNIPAM-Azo was prepared by reversible addition-fragmentation transfer (RAFT) polymerization of NIPAM in 1, 4-dioxane at 80 degrees C under N-2 atmosphere, azodiisobutyronitrile as initiator. The structure of DDMAT-Azo was characterized by nuclear magnetic resonance (NMR) and fourier transform infrared spectra, and PNIPAM-Azo was characterized by NMR spectra and Gel Permeation Chromatography (GPC). The result from GPC showed the numerical average molecular weight of PNIPAM-Azo was 3870 and its molecular weight distribution index was 1.31. Furthermore, thermo- and light-responsive hydrogel was obtained by introducing PNIPAM-Azo. Both PNIPAM-Azo and the hydrogel showed good light sensitivity and thermo sensitivity. Such double-stimuli sensitive hydrogel will be applied in biomaterials such as sensor, drug controlled release, information storage etc.