PCL(5k)-PEG(3k)-N3 is a self-assembling block copolymer with polycaprolactone (PCL) as hydrophobic segment and PEG as hydrophilic block. The azide is reactive with cylooctyne (DBCO/BCN) via copper-free click chemistry or with terminal alkyne via Cu-catalyzed click chemistry. The polymer can be used to prepare nanoparticles for drug delivery. Reagent grade, for research purpose.