Polyhydrazides based on 2,5-bis(4-carboxymethylene phenyl)-3,4-diphenyl thiophene

A series of polyhydrazides was synthesized from a novel dicarboxylic acid, 2,5-bis(4-carboxymethylene phenyl)-3,4-diphenyl thiophene (V) and or terephthalic acid and isophthaloyl or terephthaloyl dihydrazide by Yamazaki’s phosphorylation method using triphenyl phosphite as condensing agent. Polyhydrazides were characterized by IR spectroscopy solubility, viscosity, thermogravimetric analysis and X-ray diffraction studies.The polymers were obtained in quantitative yields. Polyhydrazides had viscosities in the range of 0.25–0.70 dL/g. The polymers derived from novel diacid (V) showed enhanced solubility than the polymers derived from terephthalic acid, which may be attributed to the presence to bulky pendant phenyl group and methylene spacer group in the polymer backbone. Polymers were soluble in most of the common aprotic polar solvents. Polyhydrazides showed considerable weight loss in the temperature range of 300–400 °C which is due to the cyclodehydration, leading to the formation of corresponding polyoxadiazoles. They showed Tmax in between 500 and 600 °C which is essentially the decomposition of the polyoxadiazoles. X-ray diffraction studies showed that polyhydrazides were amorphous in nature.