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(epsilon-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 epsilon-CL using an alpha-carboxylic acid-omega-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 (mu(2)/Gamma(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.