It is found that acrylamide gel shows combined collapse-swelling behavior in dilute aqueous solution of poly(vinyl methyl ether) when transferred from the equilibrium swelling state in pure water. Namely, it starts to collapse quickly and then it is swollen again with its volume approaching the original value in water. The phenomenon can be explained by thermodynamic analysis of osmotic pressure. The re-swelling is caused by the penetration of linear polymer into the network. The analysis can also explain differences of the collapsing and re-swelling behavior between samples with different shapes.

• Received 2 June 1993

DOI:https://doi.org/10.1103/PhysRevLett.71.2497