PCL(5k)-PEG(1k)-COOH is a monofunctional linear amphiphilic polymer with carboxylic acid (COOH) terminal for bioconjugation with amine in the presence of EDC or HATU. The polymer contains a hydrophobic block (polycaprolactone (PCL)) and hydrophilic block (PEG) which can self-assemble in water and be used to prepare nanoparticles for drug delivery. Reagent grade, for research purpose.