Supramolecular polymer networks based on cucurbit[8]uril host–guest interactions as aqueous photo-rheological fluids

Abstract

We describe a low-mass fraction (≤0.75 wt%) supramolecular polymer network as an aqueous photo-rheological fluid (PRF) whose rheological properties can be easily modulated via light irradiation. This supramolecular polymer network is formed via CB[8]-assisted host–guest interactions between naphthyl-functionalised hydroxyethyl cellulose (HEC-Np), methyl viologen containing styrene copolymer (PSTMV), cucurbit[8]uril (CB[8]) and a photoisomerisable azobenzene imidazolium (AzoIm) derivative. This cellulose-based PRF can undergo a UV-triggered rapid transition from a highly viscous and rigid gel into a Newtonian-like fluid, with a decrease in zero-shear viscosity of over two orders of magnitude. Moreover, the rate of viscosity reduction of these PRFs can be tuned based on the mixture composition and duration of photoirradiation.