Two new phenyl- and naphthyl-substituted rigid-rod aromatic dicarboxylic acid monomers, 2,2'-diphenylbiphenyl-4,4-dicarboxylic acid (4) and 2,2'-di(1-naphthyl)biphenyl-4,4'-dicarboxylic acid (5), were synthesized by the Suzuki coupling reaction of 2,2'-diiodobiphenyl-4,4'-dicarboxylic acid dimethyl ester with benzeneboronic acid and naphthaleneboronic acid, respectively, followed by alkaline hydrolysis of the ester groups. Four new polyhydrazides were prepared from the dicarboxy'lic acids 4 and 5 with terephthalic dihydrazide (TPH) and isophthalic dihydrazide (IPH), respectively, via the Yamazaki phosphorylation reaction. These polyhydrazides were amorphous and readily soluble in many organic solvents. Differential scanning calorimetry (DSC) indicated that these hydrazide polymers had glass transition temperatures in the range of 187-234 degrees C and could be thermally cyclodehydrated into the corresponding oxadiazole polymers in the range of 300-400 degrees C. The resulting poly(1,3,4-oxadiazole)s exhibited T-g's in the range of 252-283 degrees C, 10% weight-loss temperature in excess of 470 degrees C, and char yield at 800 degrees C in nitrogen higher than 54%. These organo-soluble polyhydrazides and poly(1,3,4-oxadiazole)s exhibited UV-Vis absorption maximum at 262-296 and 264-342 nm in NMP solution, and their photoluminescence spectra showed maximum bands around 414-445 and 404-453 nm, respectively, with quantum yield up to 38%. The electron-transporting properties were examined by electrochemical methods. Cyclic voltammograms of the poly(1,3,4-oxadiazole) films cast onto an indium-tin oxide (ITO)-coated glass substrate exhibited reversible reduction redox with E-onset at -1.37 to -1.57 V versus Ag/AgCl in dry NN-dimethylformamide solution. (c) 2006 Wiley Periodicals, Inc.