PCL(5k)-PEG(1k)-Thiol has a terminal thiol which is reactive with maleimide via thioether linkage formation or with SPDP via disulfide bond formation. The amphiphile polymer contains a hydrophilic PEG block and a hydrophobic polycaprolactone (PCL) block. Upon dispersion in water, the polymer can self-assemble to form micelles and can be used to encapsulate hydrophobic drugs. This polymer can be used to prepare drug-loaded nanoparticles for controlled release drug delivery. Reagent grade, for research purpose.