Swelling equilibria of poly(N-isopropylacrylamide) gel in glucose and starch aqueous solution

Swelling equilibria of poly(N-isopropylacrylamide) (NIPA) gel in starch–water and glucose–water aqueous solutions were measured at 20, 25, 30 and 33°C. Furthermore, solvent concentrations inside and outside the gel were measured at 20°C. The gel exhibited continuous deswelling behavior in starch–water aqueous solution. A large amount of starch could hardly penetrate into the gel network. On the other hand, a volume phase transition of the gel was observed in glucose–water aqueous solution. A significant amount of glucose could penetrate into the gel network. A solution model, based on the Flory–Huggins formula coupled with osmotic pressure by rubber elasticity proposed by Flory, was adopted to correlate the phase behavior of the gel in starch–water and glucose–water aqueous solutions. The volume change behavior and the equilibrium concentrations inside and outside the gel were successfully correlated by using the model.