ABSTRACT
The success of gas separation processes based on polymeric permselective membranes ultimately depends on the gas transport properties of the polymeric membrane material. The rate of gas permeation through a membrane is determined by the permeability coefficient, which is the product of physically more fundamental thermodynamic and kinetic parameters: solubility coefficient, diffusivity coefficient. Sorption and diffusion parameters are most commonly measured by means of simple sorption or permeation experiments. The permeability coefficient of simple weakly sorbed gases in rubbery polymers usually remains sensibly constant in the pressure range typically employed in practice. In glassy polymers, on the basis of the simple dual mode sorption and transport models, the treatment of plasticization is immediately applicable to the dissolved penetrant molecules. The dual mode mixed gas transport treatment is immediately applicable to polymeric media containing permanent specific sorption sites. The chapter also focuses on modeling the dependence of gas permeability and selectivity properties on polymer structure at the molecular level.
