Adiabatic polymerization of ε‐caprolactam in presence of lithium chloride, 1. Thermodynamic and Kinetic aspects

The activated anionic polymerization of ε‐caprolactam in presence of LiCl (up to 10 wt.‐%) is studied under quasi‐adiabatic conditions. The temperature increase of the system, after proper corrections for the heat exchange with the surroundings, allows to evaluate the enthalpies of polymerization δHp and to correlate their variations with the specific interactions of LiCl with monomer and polymer. The sharp decrease of −δHp as function of LiCl content is attributed to the stabilizing effect of the ion‐dipole interactions, which is higher for the monomer‐salt pair than for the polymer‐salt mixture. The initial rates of polymerization are enhanced by a few percents of added LiCl, with a maximum at about 3 wt.‐%. The relative influence of various physical factors on the polymerization kinetics and thermodynamics is discussed.