The aim of this work is the kinetic and thermodynamic study (by differential scanning calorimetry (DSC) and proton nuclear magnetic resonance (H-1-NMR)) of the polymerization of epsilon-caprolactone initiated by ammonium decamolybdate. By. means of isothermal kinetics, enthalpies of reaction in the range 150-160 degrees C, as well as constant rates of polymerization (using an nth-order kinetics function model), were determined. From an Arrhenius plot, activation energy (E-a = 85.3 kJ/mol) and preexponential factor (A = 1.78 x 10(8) min(-1)) were estimated. Using dynamic methods, crystallization and melting temperatures for the polymer obtained in situ were derived. Kinetic data for polymerization (obtained by H-1-NMR) were fitted to 13 different model reaction functions. It was found that power law equations represent better the conversion versus time plots for this system. On the basis of experimental facts, a coordination-insertion mechanism involving molybdenum(V) species is proposed. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 2288-2295, 2010