Relaxation phenomena in dense glassy polymer membranes

Dense polymeric films can be used as permeation-selective barriers which change the composition of a fluid by differences in solubility and/or diffusivity of fluid components in the membrane material. In general glassy polymers show rather high selectivities, but usually in combination with low fluxes. Since membrane fluxes are inversely proportional to the selective barrier thickness, membranes are made as thin as possible. For pervaporation membranes the approach to prepare thin membranes failed with respect to the selectivity of the membrane. In literature membrane selectivities were reported to decrease with decreasing membrane thickness. Furthermore the membrane preparation procedure by drying a polymer solution cast on a suitable support influences the selective permeation.