Phase transition in swollen gels

Summary

The effect of the concentration of diluent (water) at the formation of polyacrylamide networks with a small content of sodium methacrylate (mole fraction of MNa groups in the PAAm chain x_MNa=0.012) on the swelling and mechanical equilibria of gels in acetone-water mixtures was investigated. With increasing polymer content at network formation both the extent of phase transition Δ (determined by a change in the macroscopic dimensions of gels) and the critical value of the interaction parameter χ_c (given by the composition of the acetonewater mixture at the collapse) decrease; the observed dependences are in a semiquantitative agreement with the theory. The observed jumpwise change in the modulus of gels correlates well with a change in the gel volume at the collapse.