Ellipsopermeation - On the interplay of swelling and permeation of polymers with intrisicmicroporosity

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Polymer membranes have demonstrated over the past decades to be very valuable assets in separating molecular gas mixtures such as air, natural gas, biogas, ammonia reactor off-gas and propylene from drying of polypropylene. Classically, only few polymers are used in such membranes; they all work according to the solution-diffusion mechanism combining a dissolution of the permeating gas into the membrane material and subsequent diffusion into the direction of lower chemical potential. Currently, a new class of polymers with exceptional inverse selective properties emerges for gas separation applications: Polymers with Intrinsic Microporosity (PIM). They have remarkable mixed gas permeation properties as (a) they are glassy and (b) they permeate the larger species selectively over small inert gas molecules. The latter is coined inverse-selective. Their transport mechanism in gas mixtures however is very little explored nor understood. We propose to perform first-of-a-kind permeation experiments on such PIMs with varying feed and permeate gas activity while measuring simultaneously the swelling behaviour of the PIMs with in-situ ellipsometry. Our unique experimental system allows for unprecedented experimental analysis of the transport behaviour under controlled vapor gradients. Also, the PIM experiments will be compared to the most ideal membrane material silicone rubber (PDMS). For the first time ever, the experimental results will give fundamental insight into mass transport details of swollen PDMS and PIM membranes while measuring simultaneously the swelling degree. This rigorous experimental approach will shed light on long standing question to what extend permeate and feed activity and its corresponding concentration gradient affects the underlying mass transport phenomena in an ideal material such as PDMS as well as much more complex materials such as polymers with intrinsic porosity.