Flavylium-Supported Poly(<i>N</i>‑isopropylacrylamide): A Class of Multistimuli Responsive Polymer

Abstract

A new multistimuli responsive polymer was prepared by means of the free-radical copolymerization of <i>N</i>-isopropylacrylamide and a vinyl flavylium derivative. The polymer shows response to temperature (conferred by the <i>N</i>-isopropylacrylamide units) and pH and light stimuli (conferred by the flavylium moieties). The polymer follows the typical pH dependent network of chemical reactions of flavylium compounds in water that was studied by means of UV–vis spectroscopy and stationary fluorescence emission. Regarding the temperature response, the presence of the flavylium cation in the polymeric chains reduces the LCST, and it is possible to take advantage of this effect to photo-collapse partially the polymer by irradiating the system in defined ranges of pH and temperature