The time evolution of the pair distribution function of polymeric systems

Summary

The stress tensor of a polymeric system, solution or melt, is the sum of “single molecule” terms which may be expressed as integrals involving the distribution function in the phase space of a single molecule and “intermolecular” terms which involve the distribution function in the configuration space of pairs of molecules. The evaluation of the single molecule terms is usually based on the solution of the “diffusion” equation in the configuration space of a single molecule. In the present development, an analogous “diffusion” equation in the configuration space of a pair of molecules is developed. The development is based on a generalization of the “time-smoothing” ideas introduced by Kirkwood. Expressions are obtained for the various friction coefficients as time correlation functions.