Synthesis of polyamide-pyrazolones from 2,2′-disubstituted bis(4-ethoxymethylene-5-oxazolone) and aromatic dihydrazines

A new class of polyamide-pyrazolones was synthesized by the vinylogous nucleophilic substitution polymerization, which was followed by rearrangement, from 2,2′-p-phenylenebis(4-ethoxymethylene-5-oxazolone) and aromatic dihydrazines. Solution polymerization was carried out in polar aprotic solvents under mild conditions to yield polymers having inherent viscosities in the range of 0.5–1.2 quantitatively. The polymer derived from bis(4-hydrazinophenyl) sulfone was readily soluble in strongly polar solvents, while that from bis(4-hydrazinophenyl)methane was partially soluble or swelled in these solvents. The polyamide-pyrazolones which are presumed to contain some intermediate oxazolone structure showed a low level of thermal stability.