Eight novel polyhydrazides (PHa4-h3) were prepared from the reaction of two novel diacids, 5-(2-(6-methyl pyridine-2-yl)-1,3-dioxo isoindoline-6-carboxamido) isophthalic acid (3) and 5-(2-(4-methyl pyridine-2-yl)-1,3-dioxo isoindoline-6-carboxamido) isophthalic acid (4), with four dihydrazides by interfacial polycondensation. These polymers have moderate inherent viscosities (0.12-0.17 dL/g) and are readily soluble in polar aprotic solvents. They start to decompose (T-10%) above 187 degrees C and display glass transition temperatures in the range of 130.3-156.3 degrees C. All polymers could be thermally converted into the corresponding polyoxadiazole approximately in the region of 250 degrees C, as evidenced by the DSC thermograms. All of the above polymers were fully characterized by FT-IR and (HNMR)-H-1 spectroscopy, TGA, DSC, and inherent viscosity measurement.