PCL(3k)-PEG(5k)-COOH is a monofunctional amphiphile polymer which can form micelles in water. The polymer contains a hydrophobic polycaprolactone (PCL) block and hydrophilic PEG block which can be used to prepare nanoparticles for drug delivery. The carboxylic acid (COOH) is reactive with amine in the presence of activator, such as HATU or EDC. Reagent grade, for research purpose.