mPEG(1k)-PCL(5k)-COOH is an amphiphile block copolymer with carboxylic acid terminal group which can react with amine in the presence of HATU or EDC to form a stable amide linkage. The hydrophobic and hydrophilic segments of this copolymer are made of polycaprolactone (PCL) and polyethylene glycol (PEG), respectively. The biodegradable polymer can form micelles in aqueous media which can be used to entrap or encapsulate drugs. Reagent grade, for research purpose.