1,4-Dioxan-2-one (PDX) was polymerized in bulk by means of aluminum triisopropoxide (Al(OiPr)3) as initiator. Thermodynamic parameters and ceiling temperature were determined from the temperature dependence of the monomer conversion over the range from 60 to 150 °C. It highlights that the thermodynamic equilibrium monomer conversion depends strongly on the final amorphous or crystalline state of poly(1,4-dioxan-2-one) (PPDX), at least below its melting temperature. The kinetics of the PDX polymerization for various monomer-to-Al(OiPr)3 ratios at 80 °C is typically first order in both monomer and initiator and characterized by an absolute rate constant of 0.08 L mol-1 s-1. Molecular weight increases regularly with monomer conversion and initial monomer-to-Al ratio, while polydispersity is kept quite narrow all along the polymerization (Mw/Mn < 1.3). Mechanistic investigations proved that Al(OiPr)3 is an efficient initiator for promoting the ring-opening polymerization that proceeds through a coordination-insertion mechanism with a selective rupture of the acyl-oxygen bond of the monomer.