Synthesis of high molecular weight nylon 6 by anionic polymerization of ε-caprolactam. Formation of cyclic oligomers

Abstract

The formation of cyclic oligomers in the process of the anionic polymerization of ε-caprolactam was studied. Cyclic oligomer contents increased with chain initiator concentration and decrease in catalyst concentration. Cyclic dimer content was much higher than that of cyclic hexamer to cyclic hexamer and sensitively influenced by the concentrations of catalyst and chain initiator in comparison with cyclic trimer to cyclic hexamer. A mechanism is proposed in which cyclic dimer is peculiarly formed at the acyl-lactam terminal group.