Lipase-catalyzed selective transformation of polycaprolactone into cyclic dicaprolactone and its repolymerization in supercritical carbon dioxide

The lipase-catalyzed selective transformation of poly(ε-caprolactone) (PCL) into dicaprolactone (DCL: 1,8-dioxacyclotetradecane-2,9-dione) and the repolymerization of DCL in supercritical carbon dioxide (scCO₂) were carried out for the establishment of a sustainable green polymer chemistry for PCL. PCL with a number-average molecular weight of M _n = 110 000 was selectively transformed into repolymerizable cyclic DCL in 90% yield using immobilized Candida antarctica lipase (lipase CA) in scCO₂ fluid by compression to 18 MPa in the presence of a small amount of water at 40 °C. The DCL obtained such was readily polymerized by lipase CA in scCO₂ to produce a PCL with an M _n of 33 000 after 6 h.

Concept of sustainable chemical recycling of PCL using an enzyme.