Photo-reversible supramolecular hydrogels assembled by α-Cyclodextrin and azobenzene substituted poly(acrylic acid)s: effect of substitution degree, concentration, and tethered chain length

Abstract

Photo‐reversible supramolecular hydrogels based on the mixture of α‐cyclodextrin (α‐CD) and azobenzene (Azo) substituted poly(acrylic acid) s were prepared. Effects of substitution degree of Azo, polymer concentration and tethered chain length on the reversible sol–gel transition of these mixtures trigged by Ultraviolet–Visible (UV–Vis) radiation were investigated through rheology and UV–Vis spectroscopy. Their zero‐shear viscosities enhanced upon increasing substitution degree of Azo, polymer concentration, and the tethered chain length between Azo grafts and backbone, while the zero viscosities decreased upon adding free α‐CD. The binding constant between α‐cyclodextrin and azobenzene, which were determined by UV–Vis spectroscopy, showed a strong dependence on the length of tethered chain.