Kinetic Gelation Modeling: Kinetics of Cross-Linking Polymerization

Abstract

A kinetic gelation model that simulates free-radical network polymerization on a lattice with a stochastic kinetic approach to enable real time calculation was used to assess how initiation rate and primary cyclization affect the overall kinetics of polymerization of difunctional monomers. Changes that cause a more uniform distribution of reacted siteshigher initiation rate or less primary cyclizationincrease the accessibility of free radicals to functional groups, lower the fraction of trapped radicals, and consequently raise the apparent propagation rate constant. On the other hand, the final conversion, determined by kinetic chain length at a given initiator concentration, drops when termination becomes more severe such as under higher initiation rate or when radical trapping worsens such as under enhanced cyclization. In addition, the model simulates the contribution of pendant functional groups to the formation of different structures. The higher the radical concentration brought by higher initiation rate or by less preferred primary cyclization, the lower the fraction of pendant functional groups to form primary cycles and the higher the fractions of pendant functional groups to form cross-links and secondary cycles.