Lipase-Catalyzed Selective Synthesis and Micellization of Poly(ethylene glycol)-block-poly(ε-caprolactone) Copolymer Possessing a Carboxylic Acid Group at the PEG Chain End

A novel poly(ethylene glycol)- block -poly(ε-caprolactone) (PEG- b -PCL) copolymer possessing a carboxylic acid group at the PEG chain end was prepared by the one-pot lipase-catalyzed polymerization of ε-CL using an α-carboxylic acid-ω-hydroxy-PEG as a macroinitiator. This synthetic approach is remarkable because it dose not require tedious chemical routes such as end-functional group changing steps and protection-deprotection steps. The PEG- b -PCL copolymer spontaneously forms a polymeric micelle with a size of 35.3 nm and a narrow polydispersity index (μ 2 /Γ 2 =0.15) in aqueous media. Furthermore, the PEG- b -PCL micelles had a negative zeta potential due to the existence of the reactive carboxylic acid groups on the surface of the PEG- b -PCL micelles, indicating that the carboxylic acid end-functionalized PEG- b -PCL copolymer was successfully prepared. Therefore, this reactive PEG- b -PCL micelle may have potential uses in the field of drug delivery systems as a targetable drug carrier.