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 m̄_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 m̄_n of 33 000 after 6 h.