Cyclic poly(e-caprolactone) synthesized by combination of ring-opening polymerization with ring-closing metathesis, ring closing enyne metathesis, or "click" reaction

This article described the synthesis of cyclic poly(ε-caprolactone) (PCL) via ring-closing metathesis (RCM), ring closing enyne metathesis (RCEM), and "click" reaction of different difunctional linear PCL. Linear PCL precursors were prepared by ring-opening polymerization (ROP) of ε-caprolactone in bulk using 10-undecen-l-ol or propargyl alcohol as the initiator, followed by reacting with corresponding acyl chloride containing vinyl or azido end group. The subsequent end-to-end intramolecular coupling reactions were performed under high dilution conditions. The suecessful transformation of linear PCL precursor to cyclic PCL was confirmed by Gel permeation chromatography, ¹H NMR, and Fourier transform infrared measurements.