Diffusion of gas molecules in the polystyrene matrix

Abstract

We have studied the diffusion of gas molecules mside an amorphous polystyrene matrix. The diffusion constant of several gases at T = 450 K in polystyrene was computed. Particular attention was given to CO 2 for terroeratures between 300 and 800 K. The temperature dependence of the diffusion constant and the relationship between the diffusion constant and the diameter of the gas molecule were analysed. We further examined the motion of the gas molecules on the short time scale not readily accessible to experimental observation. Here we used the cage overlap function which gives information on the typical cage sizes and distribution times. On the short time scale the gas molecules show a hopping behaviour The distribution of the time period between hopping events, the distance between the cages and the size of the cages in the polystyrene matrix in the presence of guest molecules were calculated. Through the analyzing, we gel a clearer picture from the behaviour of gas molecules on short time scale in the polymer matrix.