AbstractA series of poly(hydrazooxalyl)s (2) is prepared by self polycondensation of oxalohydrazide (1a) and by polycondensation of various derivatives of oxalic acid with1aor hydrazine hydrate under a variety of reaction conditions. The molecular weights of the polymers were found to remain low. IR spectroscopy, X‐ray diffraction, and thermogravimetry were used to study the structure and thermal properties of the prepared polymers. The structure and properties of the polymers were found to depend largely on the monomers and the reaction conditions used in the synthesis, most polymers being partially cyclodehydrated and semicrystalline.2seems to possess an extended planar zigzag chain conformation similar to that of polyamides of aliphatic acids, although several crystalline modifications were observed for this polymer. It could also be enolized with strong bases and behaves like a polyelectrolyte in aqueous base solution