Synthesis, characterization, and comparison of properties of novel fluorinated poly(imide siloxane) copolymers

Four new poly(imide siloxane) copolymers were prepared by a one-pot solution imidization method at a reaction temperature of 180 degrees C in ortho-dichlorobenzene as a solvent. The polymers were made through the reaction of 0-diphthaleic anhydride with four different diamines-4,4'bis(p-aminophenoxy-3,3"-trifluoromethyl) terphenyl, 4,4'bis(3"-trifluoromethyl-p-aminobiphenyl ether)biphenyl, 2,6-bis(3'-trifluoromethyl-p-aminobiphenyl ether)pyridine, and 2,5-bis(3'-trifluoromethyl-p-aminobiphenylether)thiopene- and aminopropyl-terminated poly- dimethylsiloxane as a comonomer. The polymers were named 1a, 1b, 1c, and 1d, respectively. The synthesized polymers showed good solubility in different organic solvents. The resulting polymers were well characterized with gel permeation chromatography, IR, and NMR techniques. H-1-NMR indicated that the siloxane loading was about 36%, although 40 wt % was attempted. Si-29-NMR confirmed that the low siloxane incorporation was due to a disproportionation reaction of the siloxane chain that resulted in a lowering of the siloxane block length. The films of these polymers showed low water absorption of 0.02% and a low dielectric constant of 2.38 at 1 MHz. These polyimides showed good thermal stability with decomposition temperatures (5% weight loss) up to 460 degrees C in nitrogen. Transparent, thin films of these poly (imide siloxane)s exhibited tensile strengths up to 30 MPa and elongations at break up to 103%, which depended on the structure of the repeating unit. The rheological properties showed ease of processability for these polymers with no change in the melt viscosity with the temperature. (c) 2007 Wiley Periodicals, Inc.