The solvent-free multi-walled carbon nanotubes (MWNTs) nanofluids are obtained through acid-base reaction and hydrogen bond roles with hyperbranched poly(amine-ester) (HPAE). MWNTs content is 16.8 wt%. The functionalized MWNTs exhibit liquid-like behavior in absence of solvent at room temperature. Correspondingly, the dense surface coverage is one modifying molecule per 30 carbon atoms on the surface of MWNTs. The functionalized MWNTs are soluble in good solvent of HPAE, but insoluble in non-solvent of HPAE. Their dispersibility, high thermal stability and ability to flow at room temperature make them attractive as lubricants, plasticizers and film-forming precursors. (C) 2009 Elsevier Ltd. All rights reserved.