A fascinating nanoobject, diblock polymer brushes with a hard core of multiwalled carbon nanotubes (MWNTs) and a relatively soft shell of poly(methylmethacrylate)-block-polystyrene (PMMA-b-PS), was easily constructed by in situ reversible addition fragmentation chain transfer polymerization (RAFT) of methylmethacrylate followed by styrene (St) on the modified convex surfaces of MWNTs (MWNT-PMMA). The structure and morphology of the hybrid nanomaterials were characterized by FTIR, TEM, SEM, NMR, DSC and TGA. The results showed that both styrene and acrylate type monomers can be easily initiated and then propagated on the MWNT sidewalls via the in situ RAFT approach, and the length of the PS blocks increases with increasing St:MWNT-PMMA weight feed ratio. (c) 2006 Elsevier Ltd. All rights reserved.