Glass transition temperature and chain flexibility of ethylene-norbornene copolymers from molecular dynamics simulations

Model chains of ethylene-norborene copolymers were built up using the resutls of C-13 NMR spectral analysis of copolymer samples synthesized with metallocene-based catalysts. Our models satistically reproduce the microstructure, composition, and tacticity of the copolymer chains of experimental samples. They were used to test of MD simulations are suitable to investigate the relationships between microstructure and macroscopic properties. In particular, MD simulations were applied to calculate the glass transition temperature and to study the chain flexibility by the analysis glass transition temperature and to study the chain flexibility by the analysis of ACF of specific virtual bonds. Plots of specific volume versus temperature computed for models of four copolymer samples having different microstructures and norbornene contents yield T-g values in good agreement with experiments. Moreover, comparison of the ACFs provides some qualitative indications about the relationship between chain stereochemistry and T-g.