4,4＇-(1,4-Phenylenedioxy)dibenzoic acid as well as the 2-methyl-, 2-tert-butyl-, or 2-phenyl-substituted derivatives of this dicarboxylic acid were synthesized in two main steps from p-fluorobenzonitrile and hydroquinone or its methyl-, tert-butyl-, or phenyl-substituted derivatives. Polyhydrazides and poly(amide-hydrazide)s were prepared from these bis(ether benzoic acid)s or their diacyl chlorides with terephthalic dihydrazide, isophthalic dihydraside, or p-aminobenzoyl hydrazide by means of the phosphorylation reaction or low-temperature solution polycondensation. Most of the hydrazide polymers and copolymers are amorphous and readily soluble in various polar solvents such as N-methyl-2-pyrrolidone (NMP) and dimethyl sulfoxide. They could be solution-cast into transparent, flexible, and tough films. These polyhydrazides and poly(amide-hydrazide)s had T(g)s in the range of 167-237 degrees C and could be thermally cyclodehydrated into the corresponding poly(1,3,4-oxadliazole)s and poly(amide-1,3,4-oxadiazole)s approximately in the region of 250-350 degrees C, as evidenced by the DSC thermograms. All the tert-butyl-substituted oxadiazole polymers and those derived from isophthalic dihydrazide were organic soluble. The thermally converted oxadiazole polymers exhibited T(g)s in the range of 208-243 degrees C and did not show significant weight loss before 450 degrees C either in nitrogen or in air.