PCL(4k)-PEG(2k)-RhB is a nanomicellar-forming block copolymer which can be used for nanoparticles formulation and delivery of biopharmaceutical drugs. The polymer is biocompatible and biodegradable via hydrolytic attack on the ester bonds. The rhodamine B can be used for labeling the nanoparticles and investigation of their biodistribution. Reagent grade, for research purpose.