Novel polyhydrazides and polyoxadiazoles based on 1,3,4-thiadiazole moiety in the main chain with high thermal stability, good solubility, and notable antimicrobial activity

摘要

Polyoxadiazoles (PODs) and polyhydrazides (PHs) have wide potential applications; however, PODs are normally insoluble in organic solvents, do not melt, and do not express glass-transition temperature (T-g), and also PHs do not have high-temperature resistance. In this work, novel PHs based on 1,3,4-thiadiazole in the polymer main chain were synthesized by low-temperature polycondensation. New PODs were then obtained by cyclodehydration of the PHs. The thermal behavior, surface morphology, and crystalline structure were studied using differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy, and X-ray diffraction. In addition, the viscosity, solubility, UV-visible absorption, and antimicrobial activity were examined. The new polymers showed melting, T-g, high thermal stability, good solubility in polar aprotic solvents, and significant antimicrobial activities. The enhanced solubility may be attributed to the ability of thiadiazole moiety to form hydrogen bonding with the solvent molecules. Also, it can be concluded that introducing 1,3,4-thiadiazole and other bulky moieties like the oxadiazole ring into the polymer main chain encouraged more free volumes and weakened the chains packing; hence, the solubility was enhanced and T-g decreased without affecting the thermal stability. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47770.