Some thermodynamic, kinetic, and mechanistic aspects of the ring-opening polymerization of 1,4-dioxan-2-one initiated by Al((OPr)-Pr-i)(3) in bulk

1,4-Dioxan-2-one (PDX) was polymerized in bulk by means of aluminum triisop ropoxide (Al((OPr)-Pr-i)(3)) as initiator. Thermodynamic parameters and cei ling temperature were determined from the temperature dependence of the mon omer conversion over the range from 60 to 150 degreesC. It highlights that the thermodynamic equilibrium monomer conversion depends strongly on the fi nal amorphous or crystalline state of poly(1,4-dioxan-2-one) (PPDX), at lea st below its melting temperature. The kinetics of the PDX polymerization fo r various monomer-to-Al((OPr)-Pr-i)(3) ratios at 80 degreesC is typically f irst order in both monomer and initiator and characterized by an absolute r ate constant of 0.08 L mol(-1) s(-1). Molecular weight increases regularly with monomer conversion and initial monomer-to-Al ratio, while polydispersi ty is kept quite narrow all along the polymerization (M-w/M-n < 1.3). Mecha nistic investigations proved that Al((OPr)-Pr-i)(3) is an efficient initiat or for promoting the ring-opening polymerization that proceeds through a co ordination-insertion mechanism with a selective rupture of the acyl-oxygen bond of the monomer.