Light-tunable thermoresponsive behavior of branched polyethylenimine derivatives in water

Abstract

Combinatorial introduction of acyl, alkylsulfonyl and azobenzene (Ab) functionalities into amine-rich branched polyethylenimine produces dual-signal-responsive polymers with both temperature-and light-responsiveness in aqueous solutions. Light-tunable L/UCST polymers were synthesized by simple introduction of acyl and Ab groups or alkylsulfonyl and Ab groups, respectively. The phase transition temperatures of the polymers were dependent upon the ratios of the functionalities and reversibly controlled by light irradiation. More than 35 degrees C-shift of the LCST was obtained by UV-irradiation, which is the largest shift reported in water. Moreover, 19 degrees C-shift of the UCST was obtained by UV-irradiation, which is the first UCST shift reported in polymer-water binary systems. (C) 2016 Elsevier Ltd. All rights reserved.