A rigid poly(amidehydrazide): Morphology and mechanical behavior

Abstract

A wholly aromatic all-para oriented poly(amidehydrazide) has been prepared from N,N'-bis(4-aminobenzoyl)hydrazine and terephthaloyl dichloride by solution polycondensation. Films of the polymer were prepared by two processes, viz. a wet and a dry process, by using its solution in N,N-dimethylacet-amide/LiCl. Optical anisotropy, surface morphology and tensile properties of the films were studied. Polarizing optical microscopic study reveals that the films prepared by the dry process have more pronounced birefringent characteristics and greater nematic order than the films prepared by the wet process. The birefringent characteristics in the films become more and more prominent with increase in polymer inherent viscosity. Scanning electron microscopic study reveals that when the LiCI content in the polymer solution used for the film casting is low (1 wt.-%), the corresponding films, prepared either by the wet or by the dry process, have smooth surfaces. But when the LiCI content is high (>I wt.-%), only the wet process produces films with smooth surface, whereas there are microvoids on the surface of the films prepared by the dry process. Regarding the tensile study, in general, the films prepared by the dry process have higher strength and modulus, but lower elongation than the films prepared by the wet process due to a greater extent of retention of orientation in the films prepared by the dry process. The strength and modulus of the films are found to increase with increase in the polymer inherent viscosity.