PCL(5k)-PEG(3k)-MAL is a monofunctional amphiphile block copolymer with maleimide terminal which can react with thiol/cysteine via formation of a stable thioether bond. The polymer consists of hydrophobic polycaprolactone (PCL) and hydrophilic PEG. It can be used to encapsulate hydrophobic drugs for targeted drug delivery. Reagent grade, for research purpose.