Temperature and light sensitive copolymers containing azobenzene moieties prepared via a polymer analogous reaction

Four different series of polyacrylamides containing different amounts of azobenzene moieties have been synthesized via a polymer analogous reaction of poly(pentafluorophenylacrylate) (PPFPA). All copolymers were designed to exhibit a lower critical solution temperature (LCST) in aqueous solution, which was dependent on (i) the amount of incorporated chromophoric azobenzene groups and (ii) the isomerization state of the respective azobenzene group. Higher LCST values were measured for UV-irradiated solutions of the copolymers in comparison to the non-irradiated copolymer solutions. A maximum difference in the LCST of up to 7 °C was found for the copolymer poly(N,N-dimethylacrylamide) containing 8.5 mol% of azobenzene groups. Within this temperature range, a reversible solubility change of the copolymer could be induced by irradiation with light.