Thermally cross-linked diaminophenylindane (DAPI) containing polyimides for membrane based gas separations. (14th January 2019)

• Record Type: Journal Article
• Authors: Dose, Michelle E.; Chwatko, Malgorzata; Hubacek, Ivo; Lynd, Nathaniel A.; Paul, Donald R.; Freeman, Benny D.
• Is Part Of: Polymer. Volume 161(2019)
• Page Start: 16
• Page End: 26
• Publication Date: 2019-01-14
• Subjects: Diaminophenylindane (DAPI) -- Polyimides -- Thermal decarboxylation -- Cross-linking -- Pure gas permeability; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2018.11.050
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: This study aims to expand structure-property relationships of diaminophenylindane (DAPI)-containing polyimides and the influence of thermal cross-linking on gas transport properties of such materials. A polyimide synthesized from hexafluoroisopropylidene diphthalic anhydride (6FDA), DAPI, and diaminobenzoic acid (DABA) in a molar ratio of 0.5/0.33/0.17, 6FDA0.5 -DAPI0.33 /DABA0.17, was crosslinked by thermal decarboxylation. After cross-linking, pure gas permeability of 6FDA0.5 -DAPI0.33 /DABA0.17 increased with increased cross-linking time; gas permeability increased by about 30% after cross-linking at 353 °C for 40 min. This increase in permeability correlated with an increase in d-spacing measured by wide angle x-ray scattering, suggesting an increase in inter-chain spacing upon cross-linking. Minimal changes in O2 /N2 and N2 /CH4 selectivities occurred with increased thermal cross-linking time for 6FDA0.5 -DAPI0.33 /DABA0.17 . However, CO2 /CH4 and C2 H4 /C2 H6 pure gas selectivities increased with thermal treatment, suggesting a potential narrowing of free volume distribution. Graphical abstract: Highlights: A polyimide containing 6FDA, DAPI, and DABA, 6FDA-DAPI/DABA, was synthesized and characterized. 6FDA-DAPI/DABA was cross-linked above its Tg by thermal decarboxylation. Cross-linking increased d-spacing, and permeability increased by 30%. C2 H4 /C2 H6 and CO2 /CH4 ideal selectivities increased with cross-linking.