PCL(10k)-PEG(3k)-NH2 is a block copolymer which is reactive with an NHS ester to form a covalent amide bond. The polymer can self-assemble in water with polycaprolactone (PCL) core and PEG shell arrangement. The core regions can serve as reservoir for hydrophobic drugs while the shell regions not only provide protection from degradation (enzymatic or hydrolysis) but also enables a stealth behavior for successful in vivo translation of nanomedicine. Reagent grade, for research purpose.