PCL(2k)-PEG(5k)-NHS is a linear monofunctional block copolymer. The active ester group can react with an amine to form a covalent amide bond. The block copolymer consists of polycaprolactone (PCL) hydrophobic block attached to PEG hydrophilic block. It can be used to prepare micellar nanoparticles for drug delivery. Reagent grade, for research purpose.