The kinetics of anionic polymerization of ε-caprolactam initiated by alkali metal lactamates

The kinetics of anionic polymerization of e-caprolactam initiated by alkali metal (K, Na, and Li) lactamates were studied in the 135-160°C range. Based on these data and on the conductometric measurements of the polymerization systems, the chain growth was established to occur at free lactam anions and contact ion pairs. The propagation constants k p - and k p ± , the equilibrium constants of proton exchange K e , and the activation parameters of the process were determined. It was shown that k p - is independent of the counterion nature, whereas k p ± varies in the series K + > Na + > Li + . An equation describing the process rate, which is valid up to equilibrium conversions, was deduced. In deducing, variations in the concentration of reaction centers due to side reactions like Claisen condensation or crystallization of the polycaproamide formed were taken into account