Induction periods in the polymerization of lactams initiated with carboxylic acids in an anhydrous medium

Abstract

The polymerizations of capro-, enantho-, capryl- and laurolactam were investigated. It was found that polymerization initiated with aliphatic carboxylic acids proceeds prevailingly via addition of the lactam group to the carboxyl group. In the case of capro-, enantho- and capryllactam, addition of the lactam group to the forming primary amino groups also becomes operative with increasing extent of polymerization. Determination of the content of free initiator during caprolactam polymerization showed that incorporation of the initiator ended approximately at the end of the induction period. The induction period of caprolactam polymerization initiated with lauric or caproic acid is longer than for N-caproyl-6-aminocaproic acid as initiator. The acceleration of polymerization is due to the fact that addition of the first caprolactam molecule to the initiating carboxylic acid proceeds considerably more slowly than addition of the second and further molecules. © 1974.