Abstract
The equilibrium swelling curves of poly(N-isopropylacrylamide) gel are measured in four binary mixed solvent systems of water and organic alcohols. The organic alcohols chosen here are methanol, ethanol, 1-propanol, and 2-propanol, respectively. The re-entrant equilibrium swelling curves are obtained in these four binary mixed solvent systems of water and alcohols. The gel collapses into compact state when the concentration of alcohol is increased from water. The gel, then, swells again if the concentration of alcohol is increased further. The collapse transition of the gel occurs at the mole fraction of organic alcohol of Xo = 0.04 except for the system of methanol and water in which the collapse transition of the gel occurs at Xo = 0.14. We find that the re-swelling processes of the gel, in these binary mixed solvent systems, strongly depend on the species of the organic alcohols used.
