Topology and Mechanical Properties of Polymer Networks Formed Under Free Radical and Atom Transfer Radical Polymerizations

We present results of a study combining reactive Monte Carlo with coarse-grained molecular dynamics simulations to compare the kinetic evolution, topology, and mechanical properties of polymer networks synthesized by free radical (FRP) and atom transfer radical (ATRP) polymerizations. In both reaction schemes, the polymer networks were assumed to be formed by the bulk copolymerization of mono- and di-vinyl monomers, and the concentration of crosslinkers was varied. We analyzed the network topology to determine the distributions of strands, dangling chains, and primary and higher order loops. We find that, at a specified crosslinker concentration, FRP results in networks with more elastically effective strands, less dangling chains and fewer primary loops compared to ATRP. Through analysis of the true stress-elongation responses obtained from molecular dynamics simulations, we demonstrate that networks synthesized by FRP are stiffer and less extensible than their ATRP counterparts. Our results demonstrate the impact of the copolymerization mechanisms on the topology and mechanical properties of polymer networks.