Synthesis and characterization of 6FDA/3,5-diamino-2,4,6-trimethylbenzenesulfonic acid-derived polyimide for gas separation applications

Abstract A sulfonic acid-functionalized trimethyl-substituted polyimide was synthesized by reacting 4,4?-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 3,5-diamino-2,4,6-trimethylbenzenesulfonic acid (TrMSA). The properties of 6FDA-TrMSA were compared to the related 6FDA-derived analogues made from 2,4,6-trimethylbenzene-1,3-diamine (6FDA-TrMPD) 3,5-diamino-2,4,6-trimethylbenzene benzoic (6FDA-TrMCA). Compared 6FDA-TrMPD 6FDA-TrMCA, functionalization resulted in significantly lower surface area, reduced fractional free volume, tighter chain d-spacing. Consequently, displayed gas permeabilities with a commensurate increase permeability-based gas-pair selectivities. enhanced CO2/CH4 selectivity caused exclusively higher diffusion selectivity, which promoted strong hydrogen bonding induced SO3H functionalization. Permeation experiments 1:1 CO2-CH4 mixture revealed occurrence competitive sorption effects (depressing CO2 permeability) CO2-induced polymer matrix plasticization, enhancing CH4 permeability. At ~20 atm total pressure, showed permeability ~15 Barrer an equimolar mixed-gas 55, are ~2-fold performance values than those state-of-the-art used for industrial scale natural sweetening, i.e., cellulose triacetate.