Modeling of Network Formation with Conformation-Dependent Intramolecular Cross-Linking in Vinyl/Divinyl Copolymerization

A new polymerization model for network formation that takes into account conformation-dependent intramolecular cross-linking is proposed. The pendant double bonds present in an active polymer are distinguished by their graph distance from the active center. The conformation of the chain between the active center and the pendant double bonds is assumed to be Gaussian. The proposed model is applied to miniemulsion vinyl/divinyl copolymerization, where the three-dimensional (3D) size of the resulting network polymer can be measured. The simulations consider both conventional free-radical polymerization (FRP) and ideal living polymerizations. The model can explain one of key differences between FRP and living polymerization: in FRP, the pendant double bonds are consumed from the very beginning of polymerization, whereas in living polymerization, this behavior does not occur. A large number of small rings are formed by the intramolecular cross-linking, and the dimensions of network polymers formed are larger than those of randomly cross-linked homogeneous networks at the same cycle rank level. The model proposed here predicts a larger three-dimensional size than the model that does not distinguish pendant double bonds by their location. The present model challenges the development of size- and structure-dependent polymerization kinetics, aiming to overcome the limitations of classical chemical kinetics.