Experimental-Evidence For Inhomogeneous Swelling And Deformation In Statistical Gels

Polymer concentration correlations in a network swollen by a solvent are studied by small-angle neutron scattering. The network is made by statistical cross-linking of long chains in solution. At small scattering vectors, the intensity strongly increases upon swelling. Upon stretching, unusually oriented isointensity lines ("butterflies") are observed. These effects are well described by a model of fractal heterogeneities of cross-linking giving rise to nonhomogeneous swelling or deformation.