PCL(3k)-PEG(1k)-Thiol is a nanomicellar-forming block copolymer which can be used for nanoparticles formulation and delivery of biopharmaceutical drugs. The polymer is biocompatible and biodegradable via hydrolytic attack on the ester bonds. The thiol group is reactive with maleimide to form a stable thioether linkage. Reagent grade, for research purpose.