458190 Polymer Gas Separation Membranes with Tailorable Ultrafine Microporosity and Physical Aging Enhanced Transport Propertie
Ruilan Guo* (firstname.lastname@example.org), Jennifer Wiegand, Shuangjiang Luo, Ashish Kushwaha
Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556-5637
Polymer membranes with well-defined microporosity are highly desired for gas separations, wherein high microporosity enables fast gas transport while the finely tuned pore size distribution regulates selective transport. Central to a successful microporous gas separation membranes are the microcavity size distribution and their long term durability, i.e., resistance to physical aging. We report here a new series of microporous polyheteroarylenes containing shape-persistent iptycene-based building blocks in the backbone structures, several of which show superior gas separation performance outperforming the permeability-selectivity tradeoff upper bounds. Particularly, it is found that the intrinsic microporosity defined by the shape of the iptycene units offers unique opportunity to tailor the microcavity architecture in the membranes, which leads to well-defined yet tailorable bimodal microcavity size distribution. This paper will first focus on the discussions of how to exquisitely tailor the architecture of the microcavities in these iptycene-containing condensation polymers via modifying substituent groups, varying linkage geometry, adjusting backbone rigidity, or varying monomers combination to produce microporous polymer membranes to meet various gas separation needs. The synthesis and membrane properties of these new iptycene-containing polyheteroarylenes will be presented in details. Then the discussions will focus on the study of physical aging behavior of these microporous iptycene-containing membranes. Notably, unlike other reported microporous polymers that are susceptible to physical aging, all the iptycene-containing microporous polymers recently developed in our laboratory show superior resistance to physical aging. In particular, some of the aged membrane samples showed physical aging enhanced separation performance which manifests in marked increases in both gas permeabilities and ideal selectivities for several gas pairs. Microstructure analyses suggest that local chain relaxation in iptycene-polymers facilitates the formation of ultrafine microcavities leading to improved gas transport. The fundamental relationship between the microporous architecture and macroscopic transport properties will be elucidated to provide guidance in new membrane design.