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Modification of membranes to improve gas separation properties has been of considerable interest. Crosslinking is one route to modify membranes, but such studies need to be performed on thin membranes to quantify the impact of such modifications at thicknesses relevant to industrial membranes. In this study, the influences of UV irradiation and physical aging on O2 and N2 gas permeation properties...
Gas transport and mechanical properties are reported for a series of copolyimides and their corresponding thermally rearranged (TR) analogs. Random copolyimides of APAF/HAB-6FDA with various compositions were synthesized via chemical imidization from 2,2′-bis (3-amino-4-hydroxyphenyl)-hexafluoropropane (APAF), 3,3′-dihydroxy-4,4′-diaminobiphenyl (HAB), and 2,2′-bis-(3,4-dicarboxy-phenyl) hexafluoropropane...
Isomeric polyhydroxyimides based on 3,3′-diamino-4,4′-dihydroxybiphenyl (m-HAB) or 3,3′-dihydroxy-4,4′-diaminobiphenyl (p-HAB) with 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) were prepared via an ester-acid monomer. The polyhydroxyimides were then acetylated using acetic anhydride to change the ortho-functional groups on the polymer chains. These ortho-functional polyimides were...
Amorphous, high glass transition, crosslinkable poly(arylene ether)s for gas purification membranes have been synthesized. The polymers include a moiety capable of several oxidation reactions and UV crosslinking. Structural identification was confirmed by 1 H NMR and IR spectroscopy and molecular weights were determined by SEC. Two oxidation reactions of the polymers were identified, one by...
Thermal rearrangement of polyimides with ortho-position groups to polybenzoxazoles and related structures has been of recent interest for producing gas separation membranes. This study explores the influence of synthesis route and ortho-position functional group on the thermal rearrangement process and the fractional free volume of thermally rearranged (TR) polymers produced from polyimides derived...
The initiating system consisting of AlCl 3 with dialkyl ether such as di-n-butyl ether or diisopropyl ether has been successfully developed for providing a cost-effective process of synthesis of highly reactive polyisobutylenes (HRPIBs) with large proportion of exo-olefin end groups up to 93 mol% at temperatures ranging from −20 to +20 °C. The above dialkyl ethers played very important roles...
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