Characteristic phase transition of aqueous solution of poly(N-isopropylacrylamide) functionalized with spirobenzopyran

A novel functional copolymer was synthesized by modifying poly(N-isopropylacrylamide) with spirobenzopyran. The phase transition properties of the aqueous solution of this copolymer exhibited a logic-gate response to the light irradiation and to increased temperature, which has three different modes depending on the pH of the solution. Especially, a great increase in turbidity was observed even in dilute aqueous solution containing only 0.10 wt % of the copolymer although the copolymer contained spirobenzopyrans by only 1.1 mol %. It was confirmed also that the spirobenzopyran residues were isomerized by the influence of thermally induced phase transition of the same system. The main chain of thermoresponsive polymer and photoresponsive chromophores, which are linked closely together, affected each other.