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Polyhydrazides and poly(amide-hydrazide)s having inherent viscosities of 0.31–1.17 dL g-1 were prepared from two ether-naphthalene-dicarboxylic acids, 4,4’-(1,5-naphthalenedioxy)dibenzoic acid (1,5-NDA) and 4,4’-(2,3-naphthalenedioxy)dibenzoic acid (2,3-NDA) with terephthalic dihydrazide, isophthalic dihydrazide, and p-aminobenzhydrazide via the phosphorylation polycondensation reaction. Except for one example, the hydrazide polymers were essentially amorphous and readily soluble in polar organic solvents such as N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc). They could be cast into transparent, flexible, and tough films with good mechanical strengths from solution in DMAc. These hydrazide polymers exhibited glass-transition temperatures (Tgs) in the range 179–190 °C and could be thermally cyclodehydrated into the corresponding poly(1,3,4-oxadiazole)s and poly(amide-1,3,4-oxadiazole)s in the solid state at elevated temperatures. The oxadiazole polymers had Tgs of 228–242 °C (by differential scanning calorimetry) and 10% weight loss temperatures above 500 °C, as revealed by thermogravimetric analysis in nitrogen or in air.

A New Class of Aromatic Poly(1,3,4-oxadiazole)s and Poly(amide-1,3,4-oxadiazole)s Containing (Naphthalenedioxy)diphenylene Groups