Caprolacton

Caprolacton, or ε-caprolactone, is a cyclic ester (lactone) with a seven-membered ring formed by six carbon atoms and one oxygen. It is the monomer used to produce polycaprolactone (PCL), a biodegradable aliphatic polyester with wide use in industry and medicine. The ring structure gives caprolacton reactive properties that enable ring-opening polymerization to form long polymer chains.

Caprolacton is typically a colorless liquid at room temperature. It polymerizes by ring-opening polymerization to yield polycaprolactone. The polymerization is commonly catalyzed by metal-based catalysts, such as tin(II) octoate, which allow control over molecular weight and polymer architecture. The resulting PCL is semi-crystalline, with a low glass transition temperature (about −60°C) and a melting point near 60°C, contributing to its flexibility at ambient conditions.

Polycaprolactone is biocompatible and biodegradable, hydrolyzing its ester linkages in physiological environments to non-toxic products such as 6-hydroxycaproic acid. These properties, along with its processing versatility, make PCL suitable for medical devices, sutures, controlled drug delivery, and tissue engineering scaffolds, as well as biodegradable packaging and blends with other polymers to tune mechanical properties and degradation rates.

In research and industry, caprolacton and its polymers are explored for renewably sourced plastics, copolymerization with other lactones or monomers, and applications requiring a balance of elasticity, biocompatibility, and biodegradability.