Network Polymers Formed Under Nonideal Conditions.

Abstract

Abstract : Formation of polymer networks are discussed under nonideal conditions. The work accomplished falls into three categories: 1) probability models for determining molecular weight relations and network parameters, 2) study of epoxy systems, and 3) study of vinyl-divinyl systems. The general theoretical work on probability models has comprised the following: a) the crosslinking of chains with arbitrary length and site distribution, b) A3 and B2 step polymerization with cycles, and c) anionic, network-forming systems. Several nonidealities in epoxy systems have been and are being analyzed. Substitution effects and secondary reactions in epoxy-amine systems have been characterized and incorporated into a branching theory, and good agreement with experimental results obtained. Another problem in these systems is the effect of vitrification, so the variation of Tg with conversion has been studied for DGEBA-DDM and epoxy-novolac systems. In vinyl/divinyl systems, the formation of loops and the reduction in pendant double bond reactivity have been studied. A kinetic model was developed to predict the conversion of pendant double bonds to crosslinks and cycles, that information being employed in a branching theory. Good viscosity correlations were obtained. Further theoretical studies of cyclization were initiated as groundwork for systems for which cyclization may play an even larger role (e.g. in the formation of microgels).