CORRELATIONS IN NONLINEAR FREE-RADICAL POLYMERIZATIONS - SUBSTITUTION EFFECT

Polymer networks are often formed under conditions for which the history of reaction is important, but nonetheless such nonequilibrium polymerizations may be properly described by statistical methods. This is illustrated for a free-radical polymerization of a diunsaturated monomer subject to first-shell substitution effect. The distinction between first and second double bond reacted leads to long-range correlations which result in coupled integral equations as recursions rather than algebraic relations. The proper consideration of the history of the reaction gives an exact statistical treatment of the evolution of DP(w) in the pregel regime, a treatment which is compared with various approximations which avoid the complicated mathematics at the cost of not properly maintaining the structural integrity of the polymer.