Synthesis of soluble and thermally stable polyimide from new diamine bearing N-[4-(9H-carbazol-9-yl)phenyl] formamide pendent group

A new aromatic diamine monomer, N-(4-(9H-carbazol-9-yl)phenyl)-3,5-diaminobenzamide, was successfully prepared in four steps using carbazole as starting material and polymerized with three aromatic tetracaboxylic acid dianhydrides via the conventional two-stage synthesis including the polyaddition and chemical cyclodehydration to produce a series of the aromatic polyimides. The polyimides were characterized by FT-IR, ¹H NMR, and ¹³C NMR spectroscopy, differential scanning calorimetric (DSC) and thermo gravimetric analysis (TGA) analysis. The polyimides with inherent viscosities in the range of 0.38–0.46 dL/g showed excellent solubility in various solvents such as N-methyl-2-pyrrolidinone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), pyridine and dioxane. DSC showed the glass transition temperatures (T_g) in the range of 277–288 °C. TGA showed that all polymers were stable, with 10% weights loss recorded above 524 °C in air atmosphere. Preliminary tests on films of the polyimides indicate that the materials are brittle.