PCL(1k)-PEG(1k)-MAL is a thiol reactive amphiphilic polymer. The conjugation between maleimide and thiol forms a stable thioether bond. The polymer contains a hydrophobic block (polycaprolactone (PCL)) and a hydrophilic block (PEG) which can form micelles in water. This class of polymer can be used to prepare vesicle for drug delivery application. Reagent grade, for research purpose.