Relationship between Surface Energy and Gas Permeability of Polymer Films and Gas Separation Membranes

The specific free surface energy has been determined by the contact angle measurements for thin films of glassy polymers and dense membranes based on rubbery polymers. The obtained surface energy values have been compared with the coefficient of gas permeability towards nitrogen for the membranes based on investigated polymers. Regardless of the relaxation state of the polymers, linear correlation dependences have been found between the logarithm of the gas permeability coefficient and the nonpolar (dispersive) component of the surface energy of the films (membranes). For the films of glassy polymers, two parallel correlation dependences with close values of the slope tangent have been revealed. For the films of rubbery polymers, these dependences have been individual for each class of the substances. The slope tangents of the correlation dependences for glassy and rubbery polymers are opposite in sign, which is probably due to the difference in their relaxation states and, accordingly, the different nature of the free volume of these types of polymers. For the films based on poly[1-(trimethylsilyl)-1-propyne], the influence of the sample history on the value of the nonpolar component of the surface energy and gas permeability coefficient has been shown. The obtained results allow us to assume that the dispersive component of the surface energy of polymer films and dense polymer membranes can serve as a parameter for comparative evaluation of their gas permeability, and the contact angle measurements make it possible to trace the influence of the history on their surface and bulk properties.