(38b) Precursor Effects on the Structure and Properties of Polymer Networks Synthesized Using Molecular Dynamics

The effects of precursor topology on the formation, structure and mechanical properties of polymer networks are studied using coarse-grained molecular models. Three different sets of precursors are designed in a way that in the ideal limit of complete conversion they would lead to an identical network structure. Molecular dynamics is then used to virtually synthesize crosslinked polymers from these precursors and the resulting material structures and properties are compared. Little difference is observed in commonly examined properties including the radial distribution function, macroscopic statistics of network connectivity, and glass transition behaviors. The elastic modulus of the final network however depends strongly on the precursor topology. The total number of elastic strands in the network is found to correlate strongly with the elastic modulus for most of the network formation process, except at the highly-crosslinked limit where substantial discrepancy is observed between networks from different precursors. Although these final networks contain a similar level of structural defects, the choice of precursor has substantial impact on the spatial distribution of the defects, which explains the precursor dependence of their elastic modulus. Our results indicate that the choice of precursor should be an important consideration in constructing molecular models for crosslinked polymers. It also provides insights into the experimental design of such materials.