PCL(3k)-PEG(5k)-Thiol is a biodegradable block copolymer with hydrophobic polycaprolactone (PCL) and hydrophilic PEG. The polymer can be used for formulation of nanomicellar for sustained drug delivery. The terminal hydroxyl (OH) can be used for further derivatization while the terminal thiol can react with maleimide to form a stable thioether bond. Reagent grade, for research purpose.