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

在过去的几十年里，聚合物膜被证明是从聚丙烯干燥中分离空气、天然气、沼气、氨反应器尾气和丙烯等分子气体混合物的非常有价值的资产。传统上，这种膜中使用的聚合物很少；它们都是根据溶液-扩散机制工作的，该机制结合了渗透气体到膜材料中的溶解，然后扩散到化学势较低的方向。目前，一类具有优异逆选择性能的新型聚合物出现在气体分离应用中：具有固有微孔率(PIM)的聚合物。它们具有显著的混合气体渗透性能，因为(A)它们是玻璃状的，(B)它们通过小的惰性气体分子选择性地渗透到较大的物种中。后者被称为逆向选择。然而，它们在气体混合物中的传输机制却很少被探索或了解。我们建议对不同进料和渗透气体活度的PIM进行第一次渗透实验，同时用原位椭偏仪测量PIM的溶胀行为。我们独特的实验系统允许对受控蒸气梯度下的传输行为进行前所未有的实验分析。此外，PIM实验还将与最理想的膜材料硅橡胶(PDMS)进行比较。实验结果首次对溶胀的PDMS和PIM膜的传质细节有了基本的了解，同时测量了膜的溶胀度。这种严格的实验方法将揭示长期存在的问题，即渗透和进料活性及其相应的浓度梯度在多大程度上影响理想材料(如PDMS)以及更复杂的材料(如具有固有孔隙率的聚合物)中的潜在质量传输现象。

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.