PCL(1k)-PEG(3k)-NH2 has terminal amine which can react readily with an active NHS ester or with a carboxylic acid in the presence of HATU/EDC. The polymer contains both hydrophobic (PCL) and hydrophilic (PEG) blocks. It can self-assemble in water to form nanoparticles/micelles which can be used to encapsulate biopharmaceutical drugs. Reagent grade, for research purpose.