RING-OPENING POLYMERIZATION OF EPSILON-CAPROLACTONE IN THE PRESENCE OF DICARBOXYLIC-ACIDS

The ring-opening polymerization of epsilon-caprolactone (epsilon-CL) h as been investigated in the presence of succinic acid in nitrogen atmo sphere at 225-degrees-C. Analysis of the resultant polymers suggests t hat the poly(epsilon-caprolactone) (PCL) obtained has two terminal car boxylic groups. VPO, H-1 NMR and titration are used to determine the n umber-average molecular weight of the PCL obtained at epsilon-CL to ac id 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 ep silon-CL to succinic acid except for low epsilon-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 become s predominant, and the molecular weight approaches the equilibrium val ue (M(e)BAR) due to the ratio of epsilon-CL to succinic acid in the fe ed.