The poly(N-vinylcarbazole)-grafted MWNTs (MWNT-PVK) hybrid materials were synthesized in the presence of S-1-Dodecyl-S'-(alpha, alpha'-dimethyl-e-acetic acid) trithiocarbonate (DDAT)-covalently functionalized multiwalled carbon nanotubes (MWNTDDAT) as reversible addition-fragmentation chain transfer (RAFT) agent. Incorporation of the PVK moieties onto the MWNTs surface can considerably improve the solubility and processability of MWNTs. For all MWNT-PVK hybrid materials, they are soluble in some common organic solvents such as toluene, THF, chloroform, DMF and others. In contrast to the UV/Vis spectrum of DDAT-PVK, which was synthesized by use of DDAT as RAFT agent under the same synthetic condition, in the visible region, the absorption spectrum of MWNT-PVK exhibited a typical electronic absorption characteristics of solubilized carbon nanotubes, in which the ab- sorbance decreases gradually in the range of 350-600 nm. At the same level of linear transmission the MWNT-PVK with 79.2% PVK moieties in the material structure possesses best optical limiting performance in comparison with the other MWNT-PVK composites, MWNTs and C60. The significant NLO responses manifest the MWNT-PVK materials suitable candidate for viable optical limiting devices. Light scattering, originating from the thermalinduced microplasmas and/or microbubbles, is responsible for the optical limiting. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3161-3168, 2010