Intramolecular Conformational Potentials

The previously developed theory for treating the kinematics of polymers in dense media (Bahar, I.; Erman, B.; Monnerie, L. Macromolecules 1992, 25, 6309, 6315) is extended to include the influence of internal conformational energy barriers on the mechanism of motion. The method is based on the solution of a constrained equation of motion in the presence of dissipative forces due to friction. Successive solution of the equation for incremental changes in bond torsional angles up to completing one isomeric jump yields the optimal configurational rearrangements of chains of known original structure in response to bond isomerization. By repeating the method for an ensemble of Monte Carlo chains with different original conformations, the type and extent of coupling between dihedral angles, the correlation length involved in local conformational transitions, and the effective activation energies operating on a wide spectrum of viscous environments are determined as a function of the relative strength of intraand intermolecular effects. Comparison of results with those of Brownian dynamics simulations supports the adoption of the present model as a computationally efficient approach for investigating the kinematics of local motions in polymers.