Abstract
Novel diamine monomers, 2,6-bis(3'-trifluoromethyl-p-aminobiphenyl ether)pyridine (TABP) and 2,5- bis(3'-trifluoromethyl-p-aminobiphenyl ether)thiophene (TABT) have been synthesized, which lead to a number of novel fluorinated polyimides by thermal imidization routes when reacted with different commercially available dianhydrides like pyromellitic dianhydride (PMDA), benzophenone tetracarboxylic acid dianhydride (BTDA) or 2,2-bis(3,4- dicarboxyphenyl) hexafluoropropane (6FDA). The polyimides ABTP/6FDA and ABTT/6FDA are soluble in several organic solvents such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc) and tetrahydrofuran (THF). The polyimide ABTP/PMDA is only soluble in N- methylpyrollidone (NMP) whereas ABTT/PMDA is insoluble in all solvents. The polyimides ABTP/6FDA (2c) and ABTT/6FDA (3c) exhibited number-average molecular weight 32 940 (polydispersity index (PDI), 1.97) and 24 760 (PDI, 1.87) respectively. These polyimide films have low water absorption rate 0.3-0.9% and low dielectric constant 2.92-3.29 at 1 MHz. These polyimides showed very high thermal stability even up to 532 °C for 5% weight loss in synthetic air and glass transition temperature up to 287 °C (by DSC) in nitrogen. All polyimides formed tough transparent films, with tensile strength up to 115 MPa, a modulus of elasticity up to 2.91 GPa and elongation at break up to 12% depending upon the exact repeating unit structure.
Published Version
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