Synthesis and properties of polyimides based on an ether ketone diamine, 4,4′-bis(4-aminophenoxy)benzophenone

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) Va-f(H), Va-f(C) and copolyimides (CO-PI) Vb-d/m(e-f) were synthesized from II and six kinds of commercial aromatic dianhydrides (IIIa-f) via thermal or chemical imidization method. Poly(amic acid) (IVa-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,V-f(C) and (co-PI(Q) 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 Va-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 degreesC, and the temperatures of 10% weight loss (T-10) were above 529 degreesC and their residues more than 50% at 800 degreesC 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%.