Abstract
The sequential melt-solid ring-opening polymerization of glycolide was innovated and identified in order to produce high molecular weight poly(glycolic acid) (PGA), which was expected to be applicable for industrial mass production. This method as a typical procedure was carried out by using SnCl2·2H2O and 1-dodecanol as catalyst and initiator respectively at 170°C. The obtained polymer was characterized as a well-defined PGA structure by NMR and DSC, it was evaluated by SEC as having the weight average molecular weight (Mw) of 280,000 and the distribution (Mw/Mn) of 2.0. The polymer especially from the Mw was clarified to be at least comparable to the polymers reported in the previous literature or to the commercially available suture material. The polymerization rate constants (kap) were measured, and the activation energy of kap was calculated to be 110±3 kJ/mol at temperatures between 140°C and 170°C. The polymerization rate depended on the concentration of catalyst. The alcohol as initiator enhanced the polymerization rate as compared with H2O. The initiator provided the chemical structure of -COOH or -COOR at the polymer end group and its concentrations determined the molecular weight (Mw) of PGA. The polymerization temperature also influenced the Mw control of PGA.
