Investigation of Local Motions in Polymers by the Dynamic Rotational Isomeric State Model

The internal dynamics of a short sequence in a chain is studied according to the dynamic isomeric state scheme. Conformational transitions with dynamic pair correlations are considered. Resistance to dynamic rearrangements resulting from environmental effects and constraints operating at the ends of a sequence is incorporated into the calculation scheme. Calculations for a short sequence in a polyethylene chain showed that pair correlations do not significantly affect the orientational relaxation of a vector affixed to a bond of the sequence. Contribution from constraints, on the other hand, is dominant and slows down the orientational motions.