Fabrication of photochromic hydrogels using an interpenetrating chitosan network

Abstract

The synthesis of a novel interpenetrating chitosan network post-modified with spiropyran (SP) derivatives has been used to develop photochromic hydrogels. We have synthesized succinyl chitosan polymers containing a considerable number of both amines and carboxylic groups. Their intra/ inter molecular amide coupling reactions and postmodification with SP derivatives resulted in the photochromic hydrogels functionalized with chitosan-based interpenetrating polymer network structures. In this hydrogel system, SPs undergo reversible photoresponsive structural switching between a ring-closed colorless SP form and a ring-opened purple merocyanine form under specific light-irradiation conditions. Notably, the photo-mediated wettabilities and color intensities of the hydrogels increase by the increment in the molecular weight of SP-functionalized chitosans. (C) 2017 Wiley Periodicals, Inc