Scattering from network polydispersity in polymer gels

Abstract

Swollen networks possess permanent elastic constraints that induce static variations 〈δφ2〉s at a microscopic scale in the polymer volume fraction φ. It is shown that the concentration polydispersity 〈δφ2〉s/φ2 is related to the macroscopic osmotic and elastic properties of the gel. An expression is derived for the dependence of 〈δφ2〉s/φ2 on swelling. Good agreement is found with previously reported small-angle neutron scattering measurements in randomly cross-linked polyvinyl acetate and end-linked polydimethyl siloxane networks swollen in toluene.