Synthesis and characterization of novel 1,3,4‐oxadiazole‐ or 1,3,4‐thiadiazole‐containing wholly conjugated polyazomethines

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Abstract
A series of thermally stable and semiconducting polyazomethines containing 1,3,4‐oxadiazole or 1,3,4‐thiadiazole ring in the polymer backbone were synthesized by the simple solution poly‐condensation of dialdehydes with the preformed nuclei with aromatic diamines under mild conditions. To elucidate the structure and also structure‐property relationships of the polymers, model compounds were prepared under the same reaction conditions. These polyazomethines having a wholly conjugated system were yellow powders and had reduced viscosities up to 0.38 dL/g in concentrated sulfuric acid and electric conductivity as high as 10−11 S cm−1 at room temperature. Thermogravimetry showed that all the polymers were heat resistant up to around 400°C, in both air and nitrogen atmospheres. Their completely black colored charge‐transfer complexes were prepared by iodine‐doping of the polymers. The room temperature conductivity of the polymers was found to be markedly increased up to the orders of 10−6–10−7 S cm−1 upon doping. The highest value attained was 4.8 x 10−6 S cm−1. Comparison of electronic spectra of the polymers with those of the model compounds indicated the π‐electrons in the polymers are extensively delocalized along the polymer main chain.