Kinetic Studies of the Ring-Opening Bulk Polymerization of ε-Caprolactone Using a Novel Tin(II) Alkoxide Initiator

Abstract

A novel initiator, tin(II) hexoxide, has been synthesized for use in the bulk ring-opening polymerization of ε-caprolactone at 140 °C and the kinetics studied using dilatometry. The effectiveness of the new initiator was compared alongside that of the corresponding conventional system, tin(II) octoate / 1-hexanol. The results showed that tin(II) hexoxide, although effective, took time to dissolve in the monomer due to its molecular aggregation, leading to a prolonged induction period. Despite this, first-order kinetics, a high conversion (>90%) and a polycaprolactone (PCL) molecular weight sufficiently high for melt processing were obtained. The small-scale melt spinning of PCL monofilament fibers and the effect of off-line drawing on their tensile properties is also briefly described. This work highlights the potential for the further development of more soluble tin(II) alkoxides for use as initiators which can offer greater reaction control in cyclic ester polymerization.