mPEG(750)-PCL(1k)-COOH is composed of two distinct polymers with different hydrophobicity, the hydrophilic PEG block and the hydrophobic polycaprolactone (PCL). The different hydrophobicity allows the polymer to self-assemble in water forming core-shell micelles with arrangement of PCL being shieled from the water by PEG. The core regions can be used as hydrophobic drugs reservoir in controlled release drug delivery. The carboxylic acid (COOH) can react with amino molecule via activation with HATU or EDC to form an amide bond. Reagent grade, for research purpose.