Synthesis and characterization of 1,3,4‐thiadiazole‐containing polyazomethines and copolyazomethines

Abstract

AbstractNovel 1,3,4‐thiadiazole‐containing polyazomethines and copolyazomethines were synthesized by the solution polycondensation, in m‐cresol at 25°C, of aromatic dialdehydes, isophthalaldehyde and terephthalaldehyde, with 2,5‐bis (m‐aminophenyl)‐1,3,4‐thiadiazole (BMAT) and with BMAT and aromatic diamines, bis (4‐aminophenyl) ether and 1,5‐diaminonaphthalene, respectively. These polymers were tan yellow to yellow in color and had reduced viscosities up to 0.32 dL/g in concentrated sulfuric acid and electric conductivity as high as 10−9−10−11 S cm−1 at 25°C. All the polymers were insoluble in common organic solvents but dissolved completely in concentrated sulfuric acid and formic acid. However, they were readily hydrolyzed in concentrated sulfuric acid. X‐ray diffraction diagrams showed that the crystallinity of polyazomethines were low, but copolyazomethines were highly crystalline. These azomethine polymers are highly thermally and thermooxidativelly stable and exhibited no appreciable decomposition up to 400°C in both air and nitrogen atmospheres. Doping with iodine dramatically raised the conductivity and produced the dark brown‐ to completely black‐colored semiconductive polymers with a maximum conductivity of the order of 10−5 S cm−1. Electronic spectra of the undoped polymers indicated a large bathochromic shift of the π−π* absorption band (310 nm) due to CN bonds of BMAT. This result suggests that π‐electrons of the polymers are extensively delocalized along the main chain.