| Abstract: | The ring-opening polymerization of ε-caprolactone (ε-CL) has been investigated in the presence of succinic acid in nitrogen atmosphere at 225°C. Analysis of the resultant polymers suggests that the poly(ε-caprolactone) (PCL) obtained has two terminal carboxylic groups. VPO, 1H NMR and titration are used to determine the number-average molecular weight of the PCL obtained at ε-CL to acid molar ratios of 4, 8, 12, 14, 16 and 20, respectively. It is found that the molecular weight of the PCL is not related to the ratio of ε-CL to succinic acid except for low ε-CL concentrations. At a molar ratio of 14, the molecular weight of PCL reaches a maximum at a reaction time of 3 h. Beyond 3 h the ester exchange reaction becomes predominant, and the molecular weight approaches the equilibrium value (M?e) due to the ratio of ε-CL to succinic acid in the feed. |
