Self‐regulating polycondensations. IV. Ordered oxadiazole‐imide copolymers

Ordered oxadiazole‐imide copolymers are prepared from simple aminobenzhydrazide monomers by a step‐wise reaction which begins with the condensation of a diacid chloride to produce in situ a diamine containing hydrazide linkages. The in situ diamine is then reacted with a dianhydride to yield an ordered hydrazide‐amic‐acid copolymer; this precursor is converted by heating to the ordered heterocycle copolymer. Polymers prepared via this manner are identical in properties to those obtained by the reaction of a dianhydride with a diamine containing hydrazide linkages preformed by a straight forward synthesis from a dinitro precursor. Fibers spun from the soluble precursor polymers were converted via cyclodehydration to thermally stable fibers. Another polyoxadiazole‐imide was produced in similar fashion; e.g., an aminobenzhydrazide was reacted with the acid chloride of trimellitic anhydride to yield an in situ AB monomer which was polymerized to yield a precursor polyhydrazide‐amic‐acid, which in turn was converted by cyclodehydration to an AB type polyoxadiazole‐imide. Additional examples are cited of the formation of polymers from the in situ intermediates produced by the “self‐regulating” reaction of aminobenzhydrazides with acid chlorides followed by polycondensation with difunctional monomers.