Thermotropic liquid crystalline poly (hydrazone-ether)s containing thiadiazole moiety in the main chain

A new homologous series of thermotropic liquid crystalline poly(hydrazone-ether)s based on the 1,3,4-thiadiazole moiety in the main chain was synthesized by solution polycondensation of various diformyl-alpha,omega-diphenoxyalkanes with 2,5-bis(mercaptoacetic hydrazide)-1,3,4-thiadiazole. The inherent viscosity of the polymers was prepared in the range of 0.39-0.76 dl g(-1). The phase behaviour of these polymers was studied by differential scanning calorimetry, optical polarizing microscopy using a heated stage, and thermogravimetric analysis. Almost all the polymers exhibited thermotropic liquid crystalline properties. In most cases, the mesophase extends to 335degreesC, where thermal decomposition prevents further observation. Methoxy substituents on the benzene ring of these polymers lower the transition temperature significantly. (C) 2004 Society of Chemical Industry.