Effect of branching of cyclo-olefin copolymers and polycarbonate polymers on mechanical and optical properties: Ab initio and molecular simulation study

Mechanical and optical properties of branched cyclo-olefin copolymers (COC) and polycarbonate polymers (PC) were studied by molecular dynamics simulations and ab initio calculations. In addition, the effect of structural modifications of the polycarbonate on the optical properties was investigated by ab initio calculations. The branching of PC and COC chains was found to increase flexibility and processability of the polymers without significantly weakening the optical properties. The calculated bulk and Young's moduli were clearly lower for the branched polymers. Ab initio calculations of isotropic polarizabilities and refractive indexes were sensitive to the applied basis set and level of theory. The branching of PC and COC had a modest effect on the refractive indexes as compared with the effect of modifications of the polycarbonate backbone. The highest refractive index of the series was obtained when the backbone carbon atom of polycarbonate was replaced with sulphur atom. This observation is in agreement with experimental data.