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RESEARCH PRODUCT

United Atom Force Field for Molecular Dynamics Simulations of 1,4-Polybutadiene Based on Quantum Chemistry Calculations on Model Molecules

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We present a united atom force field for simulations of 1,4-polybutadiene based on ab initio quantum chemistry calculations on model molecules. The geometries and energies of conformers and rotational energy barriers in model alkenes and dienes have been determined from high-level quantum chemistry calculations. A rotational isomeric state (RIS) model for 1,4-polybutadiene based on the conformer geometries and energies of the model molecules has been derived. The characteristic ratio and its temperature dependence for cis-1,4-polybutadiene and trans-1,4-polybutadiene, and the characteristic ratio of a random copolymer of cis and trans units, as predicted by the RIS model, are in good agreement with experimental values, thereby supporting the accuracy of the quantum chemistry calculations. Torsional potentials for the united atom force field have been parametrized to reproduce the quantum chemistry conformer energies and rotational energy barriers for rotations about the C(sp2)−C(sp2), C(sp2)−C(sp3), and C...