A rigid poly(amidehydrazide): Morphology and mechanical behavior

A wholly aromatic all-para oriented poly(amidehydrazide) has been prepared From N,N'-bis(4-aminobenzoyl)hydrazine and terephthaloyl dichloride by solu tion polycondensation. Films of the polymer were prepared by two processes, viz. a wet and a dry process, by using its solution in N,N-dimethylacetami de/LiCl. Optical anisotropy, surface morphology and tensile properties of t he films were studied. Polarizing optical microscopic study reveals that th e films prepared by the dry process have more pronounced birefringent chara cteristics and greater nematic order than the films prepared by the wet pro cess. The birefringent characteristics in the films become more and more pr ominent with increase in polymer inherent viscosity. Scanning electron micr oscopic study reveals that when the LiCl content in the polymer solution us ed 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 th e LlCl content is high (> 1 wt.-%), only the wet process produces films wit h smooth surface, whereas there are microvoids on the surface of the films prepared by the dry process. Regarding the tensile study, in general, the f ilms prepared by the dry process have higher strength and modulus, but lowe r elongation than the films prepared by the wet process due to a greater ex tent 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 i n the polymer inherent viscosity.