GPC analysis of polymer network formation .1. Bifunctional siloxane monomer crosslinker system

The size distribution of polymer clusters in the pre-gel state was investigated as a function of the conversion by gel permeation chromatography (GPC) in order to elucidate the process of polysiloxane network formation. Polysiloxane networks were synthesized by hydrosilylation between a bifunctional monomer and a tri- or tetrafunctional crosslinker. Experimental chromatograms for the pre-gel system were compared with a theoretical one based on the distribution for the mean-square radius of gyration ((S-2)) Of polymer clusters predicted by the Flory-Stockmayer theory and the Gaussian chain statistics. Experimental chromatograms at high conversion showed a longer tailed distribution in the large (S-2) region compared with a theoretical one. A comparison of experimental chromatograms with theoretical ones suggests the structure of a precursor network in which branched clusters are linearly linked.