Enzymatic ring opening polymerization of ω-pentadecalactone using supercritical carbon dioxide

Abstract

ω-pentadecalactone, a cyclic macrolactone can be polymerized by enzymatic ring opening polymerization (e-ROP). The resulting polyester, poly(ω-pentadecalactone) has mechanical and biocompatibility properties that make it desirable for biomedical uses, especially for bone and cartilage tissue regeneration. Conventional synthesis of poly(ω-pentadecalactone) involves acid or metal catalysts and organic solvents such as toluene that can leave toxic residuals in obtained material. In this work, e-ROP of ω-pentadecalactone was performed using supercritical carbon dioxide (scCO2) as solvent, a co-solvent and Novozym 435 lipase as catalyst. Different polymerization conditions were tested to obtain high molecular weight polyesters. Reactions conducted using only scCO2 as solvent showed yields around 60wt% and molecular weights up to 33,000g/mol. Higher molecular weights were obtained when a co-solvent was used. The results also showed a strong influence of water content on enzyme and monomer concentration in reaction medium over the final polymer molecular weight and reaction yield.