Synthesis and Properties of Polyimides Based on an Ether Ketone Diamine, 4,4'-Bis(4-aminophenoxy)benzophenone

Abstract

A diamime monomer with ether-ketone group, 4,4'-Bis(4-aminophenoxy)benzophenone (II) was prepared through the nucleophilic substitution reaction of 1-chloro-4-nitrobenzene with 4,4'-Dihydroxybenzophenone in the presence of potassium carbonate in N,N-dimethylformamide, followed by catalytic reduction with hydrazine and Pd/C. Polyimides (PI) V _a−f (H), V _a−f (C) and copolyimides (co-PI) V _{b−d/m(e−f)} were synthesized from II and six kinds of commercial aromatic dianhydrides (III _a−f )via thermal or chemical imidization method. Poly(amic acid) (IV _a−f )had inherent viscosities range from 0.81 to 0.98 dL/g. PI of thermal imidization method was showed poor solubility even sulfuric acid. But PI of chemical imidization method V _e,f (C) and (co-PI(C)) could be dissolved. The reason is that the ketone group of poly(amic acid) segments linked with the terminal amino group of polymer chains during thermal imidization. PI films V _a−f (H) had tensile strengths of 101–118 MPa, elongations to break of 11–32%, and initial moduli of 2.1–2.8 GPa. The glass transition temperatures of V series were in the range of 252–278 °C, and the temperatures of 10% weight loss (T ₁₀) were above 529 °C and their residues more than 50% at 800 °C in nitrogen. V series also measured the color, dielectric constants and moisture absorptions. Their films had cutoff wavelengths between 378–421 nm, b ^* values ranging from 16.4 to 77.1, dielectric constants of 3.47–3.85 (1 MHz), and moisture absorptions in the range of 0.31–0.46 wt%.