Synthesis and properties of fluorinated polyimides. 3. Derived from novel 1,3-bis[3′-trifluoromethyl-4′(4″-amino benzoxy) benzyl] benzene and 4,4-bis[3′-trifluoromethyl-4′(4-amino benzoxy) benzyl] biphenyl

Abstract

Novel diamine monomers, 1,3-bis[3′-trifluoromethyl-4′(4″-amino benzoxy) benzyl] benzene (IV) and 4,4-bis[3′-trifluoromethyl-4′(4-amino benzoxy) benzyl] biphenyl (V) have been synthesized. These monomers lead to several novel fluorinated polyimides on reaction with different commercially available dianhydrides like pyromellatic dianhydride (PMDA), benzophenone tetracarboxylic acid dianhydride (BTDA) or 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane (6FDA). The polyimides prepared from above two monomers on reaction with 6FDA are soluble in several organic solvents such as N, N-dimethyl formamide (DMF), N, N-dimethyl acetamide (DMAc) and tetrahydrofuran (THF). The polyimides prepared from PMDA/IV is soluble in DMF and N-methyl pyrollidone (NMP) on heating, whereas V/PMDA is insoluble in all solvents. BTDA/IV polyimide is also soluble in NMP, DMF and DMAc. These polyimide films have low water absorption rate 0.2–0.7% and low dielectric constant 2.74–3.2 at 1 MHz. These polyimides showed very high thermal stability even up to 531 °C for 5% weight loss in synthetic air and glass transition temperature up to 316 °C (by DSC) in nitrogen. All polyimides formed tough transparent films, with tensile strength up to 148 MPa, a modulus of elasticity up to 2.6 GPa and elongation at break up to 31% depending upon the exact repeating unit structure.