Synthesis and properties of fluorinated polyimides.: 1.: Derived from novel 4,4"-bis(aminophenoxy)-3,3"-trifluoromethyl terphenyl

A new diamine monomer, 4,4"-bis(aminophenoxy)-3,3"-trifluoromethyl terphenyl (ATFT) was synthesized that led to a number of novel fluorinated polyimides by solution as well as thermal imidization routes when reacted with different commercially available dianhydrides like pyromellatic dianhydride (PMDA), benzophenone tetracarboxylic acid dianhydride (BTDA), or 2,2-bis(3,4-dicarboxyphenyl) hexafluorpropane (6FDA). The polyimides ATFT/BTDA and ATFT/6FDA derived from both routes were soluble in several organic solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide. The polyimide ATFT/PMDA was only soluble in N-methylpyrollidone. The polyimide films had low water absorption of 0.3-0.7%, low dielectric constants of 2.72-3.3 at 1 Hz, refractive indices of 1.594-1.647 at 589.3 nm, and optical transparency >85%. These polyimides showed very high thermal stability with decomposition temperatures (5% weight loss) up to 532 degreesC in air and good isothermal stability; only 7% weight loss occurred at 400 degreesC after 7 h, and less than 0.6% weight loss was observed at 315 degreesC for 5 h. Transparent thin films of these polyimides exhibited tensile strengths up to 112 MPa, a modulus of elasticity up to 3.05 GPa, and elongation at break up to 21% depending on the repeating unit structure. (C) 2002 Wiley Periodicals, Inc.