Synthesis and properties of organosoluble polyimides based on 4,4′‐bis(4‐amino‐2‐trifluoromethylphenoxy)benzophenone

Abstract

AbstractA novel, fluorinated diamine monomer with the ether–ketone group, 4,4′‐bis(4‐amino‐2‐trifluoromethylphenoxy)benzophenone (2), was prepared through the nucleophilic substitution reaction of 2‐chloro‐5‐nitrobenzotrifluoride and 4,4′‐dihydroxybenzophenone in the presence of potassium carbonate, followed by catalytic reduction with hydrazine and Pd/C. Flourinated polyimides (PIs) 5a–f and copolyimides (co‐PIs) 5c/a–f were synthesized from 2 and various commercial aromatic dianhydrides via thermal or chemical imidization. PIs 5a–f had inherent viscosities ranging from 0.72 to 1.22 dL/g. Besides the chemical imidization of 5c(C), the 5(C) series were soluble in amide‐type solvents and even in less polar solvents, but PIs 5a–f prepared via thermal imidization were insoluble. PI films 5a–f exhibited tensile strengths ranging from 92 to 112 MPa, elongations at break from 8 to 15%, and initial moduli from 2.0 to 2.1 GPa. The glass‐transition temperatures of the 5 series were in the range of 232–278 °C, and the 10% weight‐loss temperatures were above 535 °C, with more than a 50% char yield at 800 °C in nitrogen. In comparison of the PI 5 series with the analogous non‐fluorinated PIs 6 series based on 4,4′‐bis(4‐aminophenoxy)benzophenone, the 5 series revealed better solubility, lower color intensity, dielectric constant, and moisture absorption. Their PI films had cutoff wavelengths between 370 and 410 nm, b* values ranging from 9.6 to 58.3, dielectric constants of 3.05–3.64 (1 MHz), with moisture absorption in the range of 0.08–0.38 wt %. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 222–236, 2004