Properties of modified cyclo-olefin copolymers predicted by ab initio and molecular simulation techniques

Abstract

Mechanical, thermal and optical properties of modified cyclo-olefin copolymers COC were studied by molecular dynamics simulations and ab initio calculations. The COC chains were modified by substituting the norbornane rings with methyl groups and replacing ethane units with propane. A modified Dreiding 2.21 force field was developed for the molecular dynamics simulations. The bulk and Young’s moduli increased when the norbornane rings of COC were substituted with methyl groups and when the ethane units were replaced with propane. The highest glass transition temperature was obtained when the norbornane rings were substituted with methyl groups. Ab initio calculations of isotropic polarizability and refractive index were sensitive to the applied basis set and level of theory. Good agreement with available experimental data was obtained with the B3LYP/6-311G** method. Replacement of ethane units with propane lowered the refractive index significantly, whereas other structural modifications had practically no effect.