Homo- and copolymers of styrene and 4-vinylpyridine prepared by a nitroxide-mediated "living" free-radical method were grafted onto carbon black (CB) by trapping of radicals formed by the dissociation of the radical-capped polymers. The structural characteristics of the polymers and the composites were investigated by using Fourier transformed infrared spectra, nuclear magnetic resonance spectra, thermal gravimetric analysis, scanning electron microscopy and gel permeation chromotography. The composites were dip-coated on interdigitated electrodes to prepare thin film gas sensors, and their electrical responses towards methanol vapor were investigated at room temperature. It was found that the composites exhibited linear and reversible electrical responses towards methanol vapor in the range of 1000-20,000 ppm (R-2 = 0.999), and the sensitivities are highly dependent on the structure of the polymers, the content of CB and the dispersion of CB in the composites. (c) 2007 Elsevier Ltd. All rights reserved.