LIGHT-SCATTERING-STUDIES OF POLY(DIMETHYLSILOXANE) SOLUTIONS AND SWOLLEN NETWORKS

Static light scattering measurements were performed on model poly(dimethylsiloxane) (PDMS) networks swollen to equilibrium in toluene and in benzene. In comparison to solutions of linear chains of equal polymer concentration, the swollen networks scatter more light. This excess scattering of light has been analyzed in terms of concentration fluctuations due to variations in the local cross-link density. Bimodal networks of controlled distributions of molecular weights between cross-links were used to study the effects of cross-link inhomogeneities. The experimental results are compared to theoretical estimates based upon the macroscopic composition of the network. The observed discrepancy suggests the necessity for an improvement in the description of the microscopic or local swelling behavior in networks. © 1990, American Chemical Society. All rights reserved.