Liquid–crystalline solutions of polyhydrazides and poly(amide‐ hydrazides) in sulfuric acids

Para‐linked aromatic polyhydrazides and poly(amide‐hydrazides) can be dissolved in sulfuric acid of about 100% concentration to form liquid–crystalline solutions, and if the solutions are not heated excessively, they are reasonably stable and can be spun into strong fibers. Similar results can be obtained in fluorosulfonic acid and its admixtures with sulfuric acid. Polyhydrazides and copolyhydrazides based on oxalyl, terephthaloyl, chloroterephthaloyl, and 2,5‐pyridinedioyl units and poly(amide–hydrazides) based in part on such intermediates as 4‐aminobenzhydrazide and terephthalic dihydrazide were examined for formation of optically anisotropic solutions. Polymers with high proportions of meta‐ and ortho‐linked ring units were highly soluble but did not yield liquid–crystalline solutions.