Ladderlike polysilsesquioxanes (LPSs) containing chloromethylphenyl groups were synthesized from (p-chloromethyl)phenyltrimethoxysilane under basic conditions. Functionalized multiwalled carbon nanotubes (MWNTCOOH) were prepared by the acid treatment of pristine multiwalled carbon nanotubes (MWNTs). MWNTCOOH was reacted with LPS to prepare LPS-grafted MWNTs via ester linkages. The functionalization of MWNTs with LPS significantly altered the surface roughness of the MWNTs; there was a significant increase in the diameter of the MWNTs. The LPS-grafted MWNTs had a 10-20 nm thickness along the outer walls according to the functionalization of the MWNTs with LPS. An advantage of the hybrid LPS-grafted MWNTs was shown as improved thermal behavior. The composition, thermal properties, and surface morphology of the LPS-grafted MWNTs were studied by Fourier transform infrared spectroscopy, thermogravimetric analysis, energy-dispersive spectroscopy, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012