Hexa-armed star block copolymers, s-[poly(L-lactide)-b-poly(styrene-co-N-acryloxysuccinimide)](6) (s-[PLLA-b-poly(St-co-NAS)](6)) with triphenylene core have been successively prepared by the combination of ring-opening polymerization and atom transfer radical copolymerization, and they were used in the self-assembly in tetrahydrofuran, and the micelles with triphenylene core and PLLA as inner layer as well as poly(St-co-NAS) as shell were formed. After shell was cross-linked, PLLA was hydrolyzed in aqueous NaOH solution, the hollow spheres were formed. The structures, molecular weight and polydispersity index of the polymers were characterized by their H-1 NMR and FT-IR spectra, as well as GPC. Their morphologies were studied by TEM. The influence factors on the formation of various morphologies are under investigation. (c) 2005 Elsevier Ltd. All rights reserved.