The interdiffusion of solvent into polymer melt using molecular dynamics and Monte Carlo simulation techniques was investigated. The diffusion constants as function of solvent concentration were determined using the Darken equation. The Fickian diffusion behavior was also observed for absorption into polymer melt. The concentration profile of solvent fit an error function derived from Fick's second law for constant diffusivity. The diffusivity was independent of time and equal to the self-diffusion constant in the dilute solvent limit.

Molecular Dynamics Simulation of Solvent-Polymer Interdiffusion: Fickian Diffusion. Tsige, M., Grest, G.S.: Journal of Chemical Physics, 2004, 120[6], 2989-95