English: Ring-opening polymerization of ε-caprolactone, the main pathway to produce polycaprolactone as reviewed by Wim Thielemans and Marianne Labet in 2009. This file was made with ChemBioDraw Ultra 14. The digital object identifier of the reference is https://dx.doi.org/10.1039/b820162p. This image is intended to replace the original one (File:Pcl_synthesis.png) made by Berserker79 and Achim Raschka. Per the electronic supplementary information (available without subscription), heat is not always necessary.