A QUANTITATIVE THEORY OF LINEAR-CHAIN POLYMER DYNAMICS IN THE MELT - IV - COMPARISON WITH EXPERIMENTAL DIFFUSION CONSTANT DATA

The results of a recently presented theory for polymer dynamics are co mpared with experimental diffusion constant data for polyethylene, pol y (ethylene oxide), and poly (dimethyl siloxane) polymer melts. The mo lecular weight dependence of the self-diffusion constants for these sy stems is investigated. The various constants that appear in the theory are optimized using theoretical analysis and published results from c omputer simulations. The only adjustable parameters for each system ar e the friction coefficients for lateral and reptative motions. It is f ound that the same ratio of the monomer friction coefficients for late ral and reptative motions can be employed for all three experimental s ystems and for the two computer simulation systems considered. This is reasonable, since all these systems have fairly simple monomer units without large side groups. This leaves the monomer friction coefficien t for lateral motions as the only system-dependent adjustable paramete r in these calculations. Excellent agreement is found between the pred ictions of the theory and the experimental data. (C) 1998 American Ins titute of Physics.