Caprolactone

Caprolactone, commonly referred to as ε-caprolactone, is a lactone—a cyclic ester—with a seven-membered ring that comprises six carbon atoms and one oxygen. The chemical formula is C6H10O2. It is the monomer used to prepare polycaprolactone (PCL), a biodegradable aliphatic polyester.

Industrial ε-caprolactone is typically produced by Baeyer–Villiger oxidation of cyclohexanone to ε-caprolactone, using peracids or peresters as oxidants. Alternative routes include lactonization of 6-hydroxyhexanoic acid derivatives or related precursors. In practice, the material is a colorless, low-volatility liquid at ambient conditions that is relatively hydrophobic and only slowly hydrolyzes in water.

In polymer chemistry, ε-caprolactone undergoes ring-opening polymerization under suitable catalysts or initiators to form polycaprolactone. The resulting polymer is biodegradable and biocompatible, with applications in medical devices, controlled drug release, tissue engineering scaffolds, and packaging. PCL properties—such as crystallinity, molecular weight, and degradation rate—can be tailored by polymerization method and copolymerization with other monomers.

Safety: ε-Caprolactone is a skin and eye irritant and should be handled with appropriate protective equipment. It should be stored away from moisture and heat. The compound can hydrolyze to 6-hydroxyhexanoic acid under hydrolytic conditions.

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