Synthesis of polydihydropyridazinones from bis(3-benzoylpropionic acids) and aromatic dihydrazines

A new class of polydihydropyridazinones has been synthesized by the solution cyclopolycondensation in m-cresol of 4,4′-oxy- and 4,4′-ethylenebis(3-benzoylpropionic acids) with aromatic dihydrazines such as bis(4-hydrazinophenyl) sulfone and bis(4-hydrazinophenyl)methane. The polymers having inherent viscosities of 0.2–0.4 were highly soluble in a wide range of solvents including m-cresol, N,N-dimethylacetamide, and pyridine. Thermogravimetric analysis of the polydihydropyridazinones showed initial weight losses commencing at 290–350°C in both air and nitrogen.