CONTRIBUTION OF SHORT-RANGE INTRAMOLECULAR INTERACTIONS TO LOCAL CHAIN DYNAMICS

The effect of short-range intramolecular interactions on the probabili ty distribution of conformational transitions between rotamers in poly mers are examined by both numerical (Brownian dynamics simulations) an d analytical (dynamic rotational isomeric state) methods. Simulations show, in agreement with analytical results, that the time-dependent co nditional probability distributions of pair rotations are strongly aff ected by the interdependence of bond torsions. The latter are mainly i nduced by second order interactions, i.e. those occurring between pair s of atoms separated by four bonds. Comparison of numerical and analyt ical results demonstrates that the dynamic rotational isomeric state t heory satisfactorily reproduces the stochastics of local conformationa l transitions observed in simulations. The average number of rotameric jumps occurring during a given time interval increases due to the int erdependence of bond torsional states in polyethylene-like chains. Thi s feature is manifested by an increase in the number of coupled transi tions, favoring in particular gauche pair annihilations and correlated transitions among third neighboring bonds along the chain.