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- 저자 : J.G. de la Campa (검색결과 2 건)
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Comesana-Gandara, B.,Hernandez, A.,de la Campa, J.G.,de Abajo, J.,Lozano, A.E.,Lee, Y.M. Elsevier Scientific Pub. Co 2015 Journal of membrane science Vol.493 No.-
Ortho-hydroxypolyimides (HPIs) undergo thermal rearrangement processes in a solid state at high temperatures to produce thermally rearranged polybenzoxazoles (TR-PBOs), which are promising materials for gas separation membranes due to their exceptional permeability-selectivity performance. The strong dependence between the structure of HPIs and the final properties of the TR-PBOs and the high cost of the HPI precursors are considered excellent reasons for their continued study. In this work, a set of low-cost HPIs were synthetized via the reaction of 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) with 2,4-diaminophenol dihydrochloride (DAP-Cl) and 4,6-diaminoresorcinol dihydrochloride (DAR-Cl). The polyimide made from 6FDA and m-phenylene diamine (MPD) was also obtained for comparison purposes. The polyimide precursors and the corresponding TR-PBOs, which were tested as films, were thoroughly characterized. The glass transition temperature of these precursor polyimides was shown to be a function of the number of hydroxyl groups such that the lowest value corresponded to the polyimide from MPD and the highest value corresponded to that derived from DAR. The conversion rate of HPIs to PBO at different processing temperatures was determined, and the highest conversion rate matched the DAP derived polyimide. With respect to their gas separation properties after thermal treatment at 450<SUP>o</SUP>C, these HPIs gave rise to TR-PBOs with very high permeability and satisfactory permselectivity values for several gas pairs.
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R.M. Huertas,E.M. Maya,J. de Abajo,J.G. de la Campa 한국고분자학회 2011 Macromolecular Research Vol.19 No.8
A series of copolyimides containing carboxylic acid groups have been prepared from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and two diamines, 2,4,6-trimethyl-1,3-phenylenediamine and bis(4-amino-3-isopropyl-5-methylphenyl)methane. Carboxylic acid groups were introduced using 3,5-diaminobenzoic acid (DABA) as a comonomer in different proportions in both series of polyimides. The polymers were fully characterized using spectroscopic and thermal analysis techniques. The gas permeation properties of the polymer films were investigated and the results were explained mainly by anhydride formation, which depended not only on the -COOH content, flexibility, and structure of the polymer chain but also on the thermal treatment of the membrane. Copolyimides with the lowest DABA content of both series showed the best permeation properties, particularly the copolyimide that contained 25% of acid units, which showed O_2, N_2, CH_4, and CO_2 permeability coefficients close to 40, 10, 7, and 145 barrers, respectively. The gas separation properties were evaluated using three different casting solvents, N-methylpyrrolidinone, tetrahydrofuran, and acetone. At the initial stage, large differences in permeability coefficients were obtained for each copolyimide. On the other hand, after 1,000 h aging at room temperature,the membranes of each series showed similar permeability coefficients.
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