Polykaprolacton

Polykaprolacton, commonly known as polycaprolactone (PCL), is a biodegradable aliphatic polyester produced by the ring-opening polymerization of the lactone epsilon-caprolactone. The repeating unit of the polymer is [-O-(CH2)5-CO-], and the molecule can reach high molecular weights depending on the polymerization method and initiator used. PCL is a semicrystalline polymer with a low glass transition temperature of about −60 to −65 °C and a melting temperature around 60 °C, which gives it a flexible, soft feel at room temperature. It is soluble in many organic solvents, including chloroform, dichloromethane, and THF, and exhibits relatively low intermolecular adhesion due to its surface properties.

Synthesis and processing: PCL is synthesized primarily by ring-opening polymerization of epsilon-caprolactone, using catalysts such as tin(II) octoate or metal alkoxides and various initiators to control molecular weight. Processing routes include bulk, solution, and melt polymerization, enabling fabrication into films, fibers, coatings, and molded parts. PCL can be blended with other polymers or copolymerized (for example with PLA or PTMC) to tailor degradation rates, mechanical properties, and processing characteristics.

Degradation and environmental aspects: PCL is biodegradable via hydrolysis of its ester bonds. Degradation in the environment or in vivo is influenced by molecular weight, crystallinity, temperature, pH, and enzymatic activity (e.g., lipases). In biological contexts, PCL tends to degrade slowly, allowing long-term performance for implants or drug-delivery systems.

Applications: Due to biocompatibility and easy processability, PCL is widely used in biomedical applications such as sutures, drug-delivery systems, and tissue engineering scaffolds. It is also employed in packaging, specialty polymers, coatings, and additive manufacturing, where it serves as a versatile filament for 3D printing.