An amphiphilic star block copolymer (star-PCL-b-PEG) based on dendritic poly(ether-amide)(DPEA) was prepared through ring opening polymerization of εcaprolactone (CL) with a DPEA-OH dendrimer as an initiator

then coupling with isocyanate terminated linear polyethylene glycol(PEG-NCO).The molecular structure was verified by FT-IR

1H-NMR and GPC.The polymer could form micellelike nanoparticles due to its amphiphilic characteristics.The aggregates of star-PCL-b-PEG in aqueous media were fabricated by dropping deionized water into block copolymer solutions in common solvents.The micellar characteristics of star-PCL-b-PEG in water were similar to those of “crew-cut" aggregates. The star-PCL-b-PEG block copolymer was investigated by fluorescence spectroscopy

dynamic light scattering(DLS) and transmission electron microscopy(TEM).The critical micelle concentration (CMC) was determined by a fluorescence technique to be 1.623 mg/L.The hydrodynamic radius of micelles was measured to be 86.2 nm or 224.6 nm at different concentrations by DLS，and the polydispersity index(PDI) was estimated to be 0.115 and 0.197

respectively

showing that the particle size was relatively widely distributed at the higher concentration.As the concentration of copolymer increased

the more hydrophobic PCL segments easily aggregated with each other due to the hydrophobic interaction.Therefore

the polymer particles were formed from a lot of molecules. The morphology of star-PCL-b-PEG “crewcut" aggregates was studied directly by TEM

and various morphologies of crew-cut micelle-like aggregates were observed under various conditions by changing the nature of common solvents

the initial copolymer concentration and the water content. The multiple morphologies

including spheres

robs and vesicles were obtained.It was found that spheres and robs were obtained from the star-PCL-b-PEG solutions with THF as the common solvent

while vesicles were obtained from the copolymer solutions with DMF as the common solvent.