Synthesis of fully conjugated aromatic polyazomethine from AB‐type monomer using soluble precursor method

Abstract

AbstractA new AB‐type monomer, N,N‐bistrimethylsilylated p‐aminobenz‐aldehyde diethyl acetal was prepared via three steps from p‐bromoaniline as a starting material. The two‐stage polymerization involving a soluble precursor polymer process gave a poly(p‐phenylenevinylene)‐type polyazomethine, poly(1,4‐phenylene‐nitrilomethylidyne). The first stage of polymerization was carried out in tetrahydrofuran or hexamethylphosphoramide containing water at room temperature. In the second stage, the polymer was thermally converted into the final polyazomethine by heating over 300°C to form a free‐standing film. The film was reddish brown and insoluble in common organic solvents. The investigation of the first‐stage products by means of MALDI‐TOF mass spectroscopy proved the oligomers with 4‐11 repeating units per molecule. From the 1H‐NMR analysis of the model reaction, the polymerization mechanism was found to be a stepwise polycondensation of 4‐diethoxymethylaniline which was formed by removal of two silyl groups of the monomer.