Deformation-Induced Anomalous Swelling of Topologically Disordered Gels

We discuss the scaling theory of topologically disordered swollen networks and apply it to the study of uniaxially and biaxially stretched gels. While in θ-solvents the response to deformation is qualitatively similar to that of usual elastic solids, the theory predicts that under good solvent conditions there exists a range of intermediate deformations for which the gel swells normal to the stretching direction and its elongational modulus is reduced. At larger deformations there is a crossover into a new regime in which the gel is stabilized by nonlinear restoring forces. The experimental ramifications of our results are discussed.