In this study, we grafted water-soluble biocompatible polymer, poly(N-(2-hydroxypropyl)methacrylamide) (PHPMA), onto the surface of multi-walled carbon nanotubes (MWNTs). The reversible addition-fragmentation chain transfer (RAFT) agents, dithioesters, were successfully immobilized onto the surface of MWNTs first, PHPMA chains were then subsequently grafted onto MWNTs via RAFT polymerization by using dithioesters immobilized on MWNTs as RAFT agent. FTIR, XPS, H-1 NMR, Raman and TGA were used to characterize the resulting products and to determine the content of water-soluble PHPMA chains in the product. The MWNTs grafted with PHPMA chains have good solubility in distilled water, PBS buffer, and methanol. TEM images of the samples provide direct evidence for the formation of a nanostructure that MWNTs coated with polymer layer. (c) 2006 Wiley Periodicals, Inc.