Reaction mechanism of the alternating copolymerization of aziridines with cyclic imides

Abstract The copolymerizations of N‐substituted aziridines and cyclic imide were studied. N‐Ethylsuccinimide copolymerized with ethylenimine, but N‐ethylethylenimine did not copolymerize with succinimide and N‐ethylsuccinimide without catalyst. The effect of additives on the copolymerization of ethylenimine with succinimide and that of N‐ethylethylenimine with succinimide and N‐ethylsuccinimide was also examined. The rate of copolymerization of ethylenimine with succinimide was accelerated by the addition of N‐acetylethylenimine or water. The copolymerization of N‐ethylethylenimine with succinimide was initiated only by water, but N‐ethylethylenimine did not copolymerize with N‐ethylsuccinimide in the presence of water. Gas evolved on heating the copolymer of ethylenimine and succinimide was analyzed and confirmed to be ammonia. On the basis of these results the reaction mechanisms of the copolymerization of ethylenimine with succinimide or N‐ethylsuccinimide and of N‐ethylethylenimine with succinimide initiated by water are discussed.