Thermo- and Acid/base-induced Spectral Switching of a Poly(N-isopropylacrylamide) Copolymer Containing Benzopyran-based D-π-A type Dye Units

Abstract

Abstract-A thermoresponsive poly(NIPAM-co-dye) labeled with benzopyran-based D-π-A type dye was prepared by typical radical copolymerization. It can be also constructed a acid/base-induced molecular switch by modulation of intramolecular charge transfer with protonation/deprotonation. The lower critical solution temperature behavior was investigated by means of UV-vis spectroscopy which allows the measurement of the phase transition from 25°C to 45°C in aqueous DMSO solution. The morphology of the internal microstructure of the poly(NIPAM-co-dye) hydrogel was observed by scanning electron microscopy. The reversible switch could be obtained by thermal and acid/base stimuli. The effect of the lower critical solution temperature (LCST) in solutions of polymer gel is increasingly of interest to numerous academic and industrial applications such as drug delivery, fluorescent thermometer and separation systems [1][2][3][4] Keywords: D-π-A dye, pyran-based dye, poly(N-isopropylacrylamide), switch, lower critical solution temperature(LCST)Thermo