Photo-Reversible Supramolecular Hydrogels Assembled by -Cyclodextrin and Azobenzene Substituted Poly(acrylic acid)s: Effect of Substitution Degree, Concentration, and Tethered Chain Length

Photo-reversible supramolecular hydrogels based on the mixture of -cyclodextrin (-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 -CD. The binding constant between -cyclodextrin and azobenzene, which were determined by UV-Vis spectroscopy, showed a strong dependence on the length of tethered chain.