(98d) Modeling Styrene Trimer and Tetramer Interactions

The major topic of this study is the fundamental interactions governing the formation and aggregation of substituted (carboxyl) polystyrene nanoparticles. In this work, the focus is on studying interactions between larger p-carboxyl fragments, specifically p-carboxyl styrene trimers. The p-carboxyl trimer structures and their relative and binding energies were determined by Monte Carlo/Simulated Annealing (MC/SA) calculations using the general effective fragment potential (EFP2) method and the Second Order Perturbation theory (MP2) method using the 6-31+G(d) basis set. All calculations were performed using the electronic structure code GAMESS. The p-carboxyl styrene tetramer isomers were also studied, but only the EFP2 calculations are presented here. Double hydrogen bonding was favored in most of the low energy isomers. Overall, these results confirmed the findings in the previous study on styrene dimers. The EFP2 method proved to be a reliable and cost efficient alternative to high order correlation methods like MP2.