Heterogeneities in polyacrylamide gels immersed in acetone-water mixtures

Immersion of polyacrylamide gels in acetone-water mixtures with a high content of acetone leads to the formation of heterogeneous structures. The extent of heterogeneity increases as the initial swelling degree of the gel increases, or, as the polarity of the nonsolvent decreases. The nature of the deswelling curves indicates that the polymer-rich regions of the gel formed by the collapse transition block the solvent diffusion outside the gel. This prevents the equilibration of the gel volume with surroundings.