ABOUT DEFECTS IN NETWORKS MADE BY END-LINKING

We studied polydimethylsiloxane networks prepared by end-linking in th e bulk. Neutron scattering and scanning light-scattering experiments i ndicate that the networks swollen with a ''good solvent'' exhibit rath er strong spatial fluctuations of polymer concentration, which are nea rly frozen-in. We attribute this effect to the presence of ''defects'' in the network structure, which is consistent with the results of hig h frequency rheology measurements, performed on dry networks. The spec trum of static fluctuations appears to be more sensitive to a change i n the length of the precusor chains than to the proportion of dangling chains. We propose to explain this result by describing some of the n etwork non-uniformities as fluctuations in the size of the shortest cl osed circuits along the network. Copyright (C) 1996 Published by Elsev ier Science Ltd.