Abstract
Molecular diffusivities in polymeric system are important dynamic properties for design of gas barrier/vapor permeation membranes. The number of combination between polymers, penetants, and temperature is quite huge, and diffusivity prediction model in polymeric system is highly required. In order to attain the prediction model that can estimate molecular diffusivity in polymer by using only single component parameters and not using any adjustable parameter, microscopic viewpoint of molecular diffusive motion has been considered. Concretely, microscopic molecular collisions with adjacent molecules have been introduced into the existent free volume model as shell-like free volume around a penetrant molecule. As a result, a diffusivity prediction model in polymer matrices has been achieved for the first time. The required parameters for the predictive calculation are free volume, molecular surface area, and molecular volume of each single component, and in this study, they are calculated using viscoelastic property, semi-empirical quantum chemical calculation, and group contribution method respectively. The predictive ability of the model with the parameters is found to be moderately good.
