PCL(4k)-PEG(5k)-SPDP is a monofunctional block copolymer with terminal SPDP ester which is reactive thiol (SH). The copolymer consists of hydrophobic polycaprolactone (PCL) and hydrophilic PEG block which can self-assemble in water to form micelles used for controlled release drug delivery. Reagent grade, for research purpose.