EFFECTS OF FILM THICKNESS ON DENSITY AND GAS PERMEATION PARAMETERS OFGLASSY-POLYMERS

Dense films of poly(vinyltrimethyl silane) (PVTMS) and poly(trimethyls ilyl norbornene) (PTMSNB) having different thicknesses in the range l = 5-150 mu m were cast from hydrocarbon solutions. It was shown that a density is inversely proportional to the film thickness. The followin g equation holds for the density rho: l/rho = l/rho, - b/l. Permeabili ty and diffusion coefficients were determined using the time lag metho d in respect to different gases. For all the gases, diffusion coeffici ents decrease when film thickness decreases and film density increases . A correlation of diffusion coefficients with fractional foe volume w ere demonstrated. On the other hand, permeability coefficients are nea rly independent of the thickness and density. Possible mechanisms of t his behavior are discussed.