Effect of physical aging on the gas transport and sorption in PIM-1 membranes

Understanding of the properties over long time scales is a key requirement for the successful application of novel polymers as membrane materials. In this light, the physical aging of dense PIM-1 films with different previous histories was monitored for more than 4 years via parallel gas sorption and permeability measurements. The effect of aging on the individual transport parameters, permeability, solubility and diffusivity, was studied on alcohol treated membranes with high excess free volume. Thermal conditioning of these membranes led to accelerated aging and a reduction of the initial gas permeability and diffusivity of the membranes. A long-term CO2 sorption analysis showed aging affected the sorption kinetics much more than the total equilibrium sorption. This was confirmed by permeation studies with six different gases, showing that the reduction of the permeability coefficient of the samples as a function of time is almost entirely due to a reduction of the diffusion coefficient. A renewed alcohol treatment of the aged membrane led to significant rejuvenation of the membrane. To the best of our knowledge, this is the first systematic long term aging study on PIM-1 via simultaneous analysis of sorption and permeation kinetics. Mixed gas permeation measurements with a CO2/CH4 mixture and an N2/O2/CO2 mixture confirm the excellent permselective properties of the PIM-1 membranes even after long aging. [Display omitted] •The first systematic long-term aging study of PIM-1 membranes by independent sorption and permeation measurements.•Permeation and sorption studies both reveal that aging mainly affects the D coefficient and not the S coefficient.•A thermal treatment partially stabilizes the sample against further aging.•At sufficiently long time scales, the sample properties become almost independent on the previous history.•Mixed gas permeation experiments confirm excellent separation performance of an aged sample.