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°C in ortho ‐dichlorobenzene as a solvent. The polymers were made through the reaction of o ‐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. 1 H‐NMR indicated that the siloxane loading was about 36%, although 40 wt % was attempted. 29 Si‐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°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. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008