Modification of Free Volume due to Rigidness of Polymeric Matrix and Effects on Gas Transport Properties

Gas barrier properties of polymeric membranes with different rigidness of their matrix where studied by gas phase permeation measurements. Gas transport results in membranes made of epoxy resin with different cross linking densities and epoxy resin with dispersed few layer graphene fillers were discussed and compared in the framework of the free volume theory of diffusion. Transport in cellulose membranes was found to occur in the diffusion configurational regime. The physical description of the transport properties was based on positron annihilation lifetime spectroscopy measurements which allowed to evaluate experimentally the fractional free volume in epoxy resin membranes and the size of rigid elongated cavities in cellulose thin films.