mPEG(5k)-PCL(3k)-COOH is a linear amphipathic polymer with carboxyl terminal which can react with amine via activation with HATU or EDC. The hydrophobic polycaprolactone (PCL) is biodegradable via hydrolytic attack on the ester bonds. The self-assembling polymer forms micelles which can be used to entrap hydrophobic drugs for nanomedicine. Reagent grade, for research purpose.