The functionalized multi-walled carbon nanotubes (MWNT) had been prepared by free radical reaction with vinyltriethoxysilane. Polydimethylsiloxane (PDMS)based poly(urea urethane) (PUU) was also synthesized. PUU was further end-capped with aminopropyltriethoxysilane (A-silane), or with phenyltrimethoxysilane (P-silane). Fourier transform infrared (FTIR), Raman spectra and thermogravimetric analysis (TGA) confirmed the functionalization of MWNT. The M-n and M-w of PUU were 85,123 and 235,876 g/mol, respectively. Both A-silane end-capped PUU and P-silane end-capped PUU showed improved dispersion of MWNT compared with that of PUU and MWNT. Moreover, the reduced discrepancy of surface electrical resistance of the two sides of the MWNT/PUU nanocomposite film was found due to the homogeneous dispersion of MWNT. The microwave absorption and tensile strength of MWNT/PUU were also improved by the well dispersion of MWNT in PUU matrix. (c) 2006 Wiley Periodicals, Inc.