POXINAR Membrane Family for Gas Separation

Abstract

Poly­(oxindolylidene arylene)­s (POXINARs), a family polymers with high performance in terms of thermal stability properties and with ether-bond-free aromatic backbones alternating with bulky, torsion resistant oxindolylidene fragments, have been synthesized by superacid catalyzed polyhydroxyalkylation, and their useful physical properties have been assessed to determine their performance as gas separation membranes. The room temperature synthesis allows a variety of fully soluble, high-molecular-weight polymers in a single pot “click” reaction. These polymers can form flexible and transparent films, and they possess high glass transition temperatures (>500 °C); high decomposition temperatures (ranging from 500 to 524 °C); and FFVs (0.130–0.194) comparable to those reported for the polysulfone, polycarbonate, and polyarylate families. However, their selectivity–permeability combinations are very attractive because some fall close to the 2008 upper-bound limits. Membranes made from isatin and 9,9-dimethyl-9H-fluorene (2aD) display P(O2) = 15.4 Barrer for the O2/N2 gas pair and an O2/N2 selectivity of 6.4, whereas for the H2/CH4 gas pair, they display P(H2) = 170 Barrer and a H2/CH4 selectivity of 77.

Multication Cross-Linked Poly(p-terphenyl isatin) Anion Exchange Membranes for Fuel Cells: Effect of Cross-Linker Length on Membrane Performance

“…Common commercial nonfluorine-based backbones mainly include poly­(2,6-dimethyl-1,4-phenyleneoxide) (PPO), − poly­(ether ether ketone) (PEEK), , and polysulfone (PSF). , However, when the main chain contains electron-withdrawing groups, it significantly reduces the alkali resistance of the membranes. − Therefore, it is crucial to develop polymer backbones free of ether bonds for AEM materials. As displayed in Scheme a, among the possible designs for ether-bond-free backbones, superacid-catalyzed polymerization has been employed as an efficient method to fabricate poly­(arylene)-based AEMs. − Yan et al developed a series of poly­(aryl piperidinium) membranes for AEMFCs; these rigid, high-molecular-weight backbones display good alkaline stability after 2000 h in 1 M KOH at 100 °C. Recently, Zhu et al reported novel poly­(isatin biphenyl) AEMs grafted with different side-chain cations.…”

One-Step, Room Temperature Synthesis of Well-Defined, Organo-Soluble Multifunctional Aromatic Polyimides

“…The superacid-catalyzed nonstoichiometric step polymerization of aromatic hydrocarbons with carbonyl compounds (polyhydroxyalkylation) is a relatively new and very efficient synthetic technique. ,− A remarkable feature of this method is the presence of the highly reactive intermediate carbinol formed after the first hydroxyalkylation step. Even more interesting is the fact that a 10–40% excess of the carbonyl compound significantly increases the polymer molecular weight and decreases the macrocycle fraction .…”

“…The methodology has been applied to synthesize polymers (e.g., poly­(aryl piperidinium, poly­(oxindolebiphenylylene), etc.) for the preparation of gas separation membranes, , fuel cells, − and ultra- and nanofiltration. − Inspired by these promising results we have extended the application of superacid-catalyzed polyhydroxyalkylation for the synthesis of wholly aromatic PIs.…”

Mixed Matrix Membranes Based on Fluoropolymers with m- and p-Terphenyl Fragments for Gas Separation Applications

“…In this study, the developed polymeric membranes and MMMs did not display a clear tendency to fracture; this is mainly due to its high thermostability with no significant weight loss below 500 °C (under air) as observed in thermogravimetric analysis (TGA) studies (Figure and Table S1), and glass-transition temperatures were not detected before its decomposition temperature. This behavior is analogous to that of similar polymers. ,− On the other hand, the obtained MMMs withstood harsh conditions during solvent evaporation (up to 200 °C, when NMP was used as a solvent) and gas transport measurements where pressures up to 2 bar were employed. This depicts the good thermal and mechanical stabilities, at least under the conditions studied, of the obtained MMMs.…”