PHASE-TRANSITION IN SWOLLEN GELS .7. EFFECT OF CHARGE CONCENTRATION ON THE TEMPERATURE COLLAPSE OF POLY(N,N-DIETHYLACRYLAMIDE) NETWORKS IN WATER

The swelling and mechanical behavior of gels of the copolymer of diethylacrylamide (DEAAm) with a small quantity of sodium methacrylate swollen in water was investigated in the temperature range 1-80 degree C. The formation of associations in the collapsed state contributes to the overall extent of the transition; these structures give rise to stable turbid gels at elevated temperatures. Evidence for the formation of 'associated' structures is also supported by the observed independence of cloud temperature of the concentration of DEAAm, c, in the polymerization DEAAm-water mixture without the crosslinking agent in the range c equals 0. 5-80 vol%. While PDEAAm solutions are formed in the range c less than 4. 5-6 vol%, physical gels arise at higher concentrations.