Contribution of Short-Range Intramolecular Interactions to Local Chain Dynamics

The effect of short-range intramolecular interactions on the probability distribution of conformational transitions between rotamers in polymers are examined by both numerical (Brownian dynamics simulations) and analytical (dynamic rotational isomeric state) methods. Simulations show, in agreement with analytical results, that the time-dependent conditional probability distributions of pair rotations are strongly affected by the interdependence of bond torsions. The latter are mainly induced by second order interactions, i.e. those occurring between pairs of atoms separated by four bonds. Comparison of numerical and analytical results demonstrates that the dynamic rotational isomeric state theory satisfactorily reproduces the stochastics of local conformational transitions observed in simulations. The average number of rotameric jumps occurring during a given time interval increases due to the interdependence of bond torsional states in polyethylene-like chains. This feature is manifested by an increase in the number of coupled transitions, favoring in particular gauche pair annihilations and correlated transitions among third neighboring bonds along the chain.