Contribution to the alkali catalyzed polymerization of ε-caprolactam

Analysis of sodium catalyzed ϵ-caprolactam polymers indicate that after very short polymerization times ϵ-caprolactam and its cyclic oligomers are already in equilibrium with the amide groups in the polymeric chains.

Potentiometric titration experiments provide conclusive evidence that at least after dissolution of the polymer in benzylacohol at higher temperatures only carboxyl groups (neutralized by sodium) and amino groups are present, in amounts equivalent to the number of sodium atoms used as a catalyst.

The course of melt viscosity with polymerization time is explained by a redistribution of chain lengths, a process much slower than the attainment of equilibrium between chains and rings.