Geometric and electronic structure of alkane/benzene, ethylbenzene/benzene, and alkane/ethylbenzene complexes: Towards the characterization of polymer alloy composites

As a first step towards the theoretical investigation of polymer alloy composites formed by the dispersion of carbon black particles throughout a polyethylene/polystyrene blend, we discuss here the results of ab initio Hartree-Fock quantum-chemical calculations, including correlation effects via second-order Møller-Plesset perturbation theory, on small model systems. These are chosen to simulate the various interfaces that appear in the composites: the interfaces between the polymers and the graphitic surface of carbon black are modeled by the complexes formed by benzene (taken as the substrate) with methane, ethane, propane, and ethylbenzene while the polymer/polymer interface is modeled by the propane/ethylbenzene system. The functionalization of the benzene substrate with hydroxyl, amine, carboxylic, or quinoid groups is also investigated in order to determine the influence of such moieties that can be present on the carbon surface. Our main goal by studying these model systems is to characterize the primary binding interaction sites and to evaluate the energies involved in the bonding; our results can also serve as a reference for molecular mechanics calculations on more extended systems.