About “defects” in networks made by end-linking

Abstract

We studied polydimethylsiloxane networks prepared by end-linking in the bulk. Neutron scattering and scanning light-scattering experiments indicate that the networks swollen with a “good solvent” exhibit rather strong spatial fluctuations of polymer concentration, which are nearly frozen-in. We attribute this effect to the presence of “defects” in the network structure, which is consistent with the results of high frequency rheology measurements, performed on dry networks. The spectrum of static fluctuations appears to be more sensitive to a change in the length of the precusor chains than to the proportion of dangling chains. We propose to explain this result by describing some of the network non-uniformities as fluctuations in the size of the shortest closed circuits along the network.