PCL(3k)-PEG(2k)-SPDP is reactive with thiol to form a disulfide linkage. The block copolymer is amphiphilic which can self-assemble in water to form core-shell nanoparticles/micelles. The core regions contains polycaprolactone (PCL) which can be used to entrap or encapsulate hydrophobic drugs. Reagent grade, for research purpose.