Polymerization of lactams, 94 - Formation of cyclic oligomers in anionic polymerization of 6-hexanelactam

HPLC analysis of the methanol-extractable fractions of polymers was used to study the formation of cyclic oligomers during the non-activated anionic p olymerization of 6-hexanelactam initiated by sodium or magnesium salt of 6- hexanelactam and ethylmagnesium bromide at 190 degrees C. It was demonstrat ed that the nature of the counterion of the substance which initiates the a nionic polymerization has a crucial effect on the mechanism of the formatio n of the cyclic oligomers. It was proved that in the course of the 6-hexane lactam polymerization in presence of magnesium compounds, the cyclic oligom er formation is distinctly slower, as compared to the sodium 6-hexanelactam -initiated polymerization.