The in situ synthesis of the nano-assemblies of the high molecular weight ferrocene-containing block copolymer of poly(ethylene glycol)-block-poly(4-vinylbenzyl ferrocenecarboxylate) (PEG-b-PVFC) via dispersion reversible addition-fragmentation chain transfer (RAFT) polymerization was discussed. Taking the advantage of the accelerated polymerization rate of the dispersion RAFT polymerization, the nano-objects of the well-defined PEG-b-PVFC diblock copolymer with the polymerization degree (DP) of the ferrocene-containing PVFC block up to 300 were prepared. It was found that the morphology of the PEG-b-PVFC diblock copolymer nano-assemblies was dependent on the DP of the PEG and PVFC blocks, and nano-spheres favorably formed in the case of the long PEG block and vesicles containing a thick and porous membrane were formed in the case of the short PEG block and long PVFC block, respectively. Our results demonstrate that the dispersion RAFT polymerization is an effective way to prepare the high molecular weight ferrocene-containing block copolymer with interesting morphologies. (C) 2015 Wiley Periodicals, Inc.