Synthetic 6FDA‐ODA copolyimide membranes for gas separation and pervaporation: Correlation of separation properties with diamine monomers

Abstract

Copolyimides were synthesized from 4,4 0 -(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 4-aminophenyl ether (ODA) with 4-aminophenyl sulfone (DDS), 4,4 0 -methylenedianiline (MDA), 4,4 0 -bis(3-aminophenoxy)diphenyl sulfone (BADS), 4,4 0 -bis(3-aminophenoxy) benzophenone (BABP), and 2,6-bis(3-aminophenoxyl) benzonitrile (DABN) as the third monomer. Surface free energies and interfacial free energies were calculated for comparison of the membrane hydrophilicity. Gas permeation was carried out with N 2 , O 2 , H 2 , He, and CO 2 , and the moiety contributions to membrane selectivity were calculated. DDS and BADS moieties contribute negatively to the selectivities toward O 2 /N 2 , H 2 /N 2 , and He/N 2 , and the DABN moiety is favorable for improving CO 2 /N 2 selectivity. Water permeation and dehydration of isopropanol were performed, and the linear moiety contribution method was applied to study the effects of the monomer structures on the temperature and feed concentration dependencies of the permeation flux. The steric effects of DDS and BADS moieties, as well as the interactions of BABP and DABN moieties with water, account for the differences in pervaporation properties of the membranes. POLYM. ENG. SCI., 48:795-805, 1 GPU ¼ 7.5 Â 10 12 m 3 (STP) m À2 s À1 Pa À1 .Ideal separation factor a i/j for the gas pair i and j can be calculated from Eq. 2: Pervaporation ExperimentsPure water permeation was conducted at 30, 40, 50, and 608C continuously, followed by dehydration of isopropanol. The feed water content was kept at $20 wt%, while temperatures were controlled at 30-608C. Then the

Prediction of gas permeability coefficients of copolyimides by group contribution methods

“…The other parameters such as residual solvent and membrane or dense/film preparation procedure also influence the polymer structure and hence their permeability coefficients. In some studies, the permeability unit was reported as GPU; in order to convert it to Barrer, GPU was multiplied with the average film thickness [30][31][32]. However, the thickness of the selective layer is not known with high accuracy in case of asymmetric membranes, so this will also bring another source of error.…”

NH2-MIL-53(Al) and NH2-MIL-101(Al) in sulfur-containing copolyimide mixed matrix membranes for gas separation

“…For pure polymer, absorption bands at 1785, 1718, 1351 and 719 cm -1 corresponded to asymmetric and symmetric C=O stretching, C-N stretching and imide five-ring deformation [25]. Besides, the signal at 1327 cm -1 was related to the asymmetric stretching of SO2 [35]. In the case of pure MOFs, NH2-MIL-53(Al) and NH2-MIL-101(Al) bands at 3504 and 3391 cm -1 and the shoulder at 1624 cm -1 corresponded to the asymmetric and symmetric amine stretching and the N-H scissoring vibration, thus confirming the presence of amino groups in the framework [20,24].…”

Using iron (III) acetylacetonate as both a cross-linker and micropore former to develop polyimide membranes with enhanced gas separation performance

“…One glassy polymer of interest is polyimide containing 4,4 -(hexafluoroisopropylidene) diphthalic anhydride (6FDA) [8][9][10][11][12][13][14][15][16]. It consists of bulky CF 3 groups that reduce chain packing and increase chain stiffness due to steric hindrance.…”