Hydrazine-based polyimides and model compounds

The reaction of hydrazine hydrate with aromatic anhydrides may give either N-amino imides or cyclohydrazides. The conditions that favor the formation of N-aminoimides, in which the imide contains respectively a 5- and 6-membered ring, are discussed. These compounds may be reacted with aromatic anhydrides to give N-N-linked imides. The properties of a number of model compounds and polymers are described, and it is shown that those compounds which have alternating 5- and 6-membered imide rings give the maximum oxidative stability in air at 400°C.