Gas Permeation Properties, Physical Aging, and Its Mitigation in High Free Volume Glassy Polymers

Abstract

Hundreds of polymers have been evaluated as membrane materials for gas separations, but fewer than 10 have made it into current commercial applications, mainly due to the effects of physical aging and plasticization. Efforts to overcome these two problems are a significant focus in gas separation membrane research, in conjunction with improving membrane separation performance to surpass the Robeson upper bounds of selectivity versus permeability for commercially important gas pairs. While there has been extensive research, ranging from manipulating the chemistry of existing polymers (e.g., thermally rearranged or cross-linked polyimides) to synthesizing new polymers such as polymers of intrinsic microporosity (PIMs), there have been three major oversights that this review addresses: (1) the need to compare the approaches to achieving the best performance in order to identify their effectiveness in improving gas transport properties and in mitigating aging, (2) a common standardized aging protocol that allows rapid determination of the success (or not) of these approaches, and (3) standard techniques that can be used to characterize aging and plasticization across all studies to enable them to be robustly and equally compared. In this review, we also provide our perspectives on a few key aspects of research related to high free volume polymer membranes: (1) the importance of Robeson plots for membrane aging studies, (2) eliminating thermal history, (3) measurement and reporting of gas permeability and aging rate, (4) aging and storing conditions, and (5) promising approaches to mitigate aging.

Sulfonated Microporous Polymer Membranes with Fast and Selective Ion Transport for Electrochemical Energy Conversion and Storage

“…Recent development of microporous polymers,s uch as polymers of intrinsic microporosity (PIMs), provides an ew platform for designing ion-exchange membranes with molecularly defined pore structures and size-exclusion function that enable fast and selective ion transport. [8] Previous work on ion transport PIMs has been focused on PIM-1 and application in organic solvent electrolytes. [9] In addition, we reported anew generation of anion-exchange membranes derived from Tr çger base-containing PIMs, [10] and demonstrated the fast transport of hydroxide and chloride anions through the subnanometer cavities within the positively charged polymer membranes.R ecent work also demonstrated that hydroxide exchange membranes and ionomers prepared from rigid backbones present improved ionic conductivity as well as high stability.…”

Molecular‐Sieving Membrane by Partitioning the Channels in Ultrafiltration Membrane by In Situ Polymerization

“…and polymers, have attracted extensive attention . Despite the fact that great achievements have been made, these membranes still suffer from phase segregation and low durability stemming from sliding of the linear polymer chains …”

Crosslinking of addition copolymers from tricyclononenes bearing (CH3)3Si‐ and (C2H5O)3Si‐groups as a modification of membrane gas separation materials

“…For a long time, polydimethylsiloxane was one of the most gas permeable polymer . Later, glassy nanoporous Si‐substituted polymers like polynorbornenes , PIMs , and polyalkynes were synthesized that were found to be much more permeable than polysiloxanes. Furthermore, these new polymers unexpectedly displayed a salient feature for glassy polymers—the solubility‐controlled permeation of hydrocarbons .…”