The influence of intramolecular chain dynamics on the diffusion of small penetrants in semicrystalline aromatic polymers

A recently developed molecular model for diffusion in dense aromatic polyme rs, which attempts to explain penetrant jump frequencies in terms of phenyl ring partial flips, is investigated via molecular simulation. The model po lymer system under consideration in this paper corresponds to the interfaci al domains generated by the lateral chain invariant (LCI) grain boundaries between crystallites of a stiff chain polyamide, poly(p-phenylene terephtha lamide) (PPTA), and the low molecular weight penetrant selected for study i s water. Fully atomistic constraint molecular dynamics simulations are cond ucted with interatomic and intramolecular interactions described by the DRE IDING potential [S. L. Mayo, B. D. Olafson, and W. A. Goddard III, J. Phys. Chem. 94, 8897 (1990).] The coupling of the diffusive motion of water with the local polymer chain dynamics is examined at two temperatures and over a range of grain boundary densities. (C) 1999 American Institute of Physics . [S0021-9606(99)50722-8].