Penetrant diffusion in frozen polymer matrices: A finite-size scaling study of free volume percolation

Abstract

The diffusion of penetrant particles in frozen polymer matrices is investigated by means of Monte Carlo simulations of the bond fluctuation model. By applying finite-size scaling to data obtained from very large systems it is demonstrated that the diffusion process takes place on a percolating free volume cluster describable by a correlated site percolation model which falls into the same universality class as random percolation. The diverging correlation length entails a pronounced dependence of the diffusion constant on the size of the simulated system. It is shown that this dependence is appreciable for a wide range of parameters around the transition. \textcopyright{} 1996 The American Physical Society.