In this work, we present a surface functionalization procedure of only two overall steps for several conductive and nonconductive materials based on the spontaneous surface grafting of a remarkable coupling agent, p-phenylenebis(diazonium) cation (PPBD). We thoroughly characterize the thin films produced with this technique using voltammetry, UVvisible and infrared spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. Materials that can be modified include ordinary soda-lime glass, indium tin oxide (ITO), gold, glassy carbon, and a commercial screen-printed carbon paste electrode. Grafting of PPBD occurs through a solvent-dependent pathway, yielding a polyphenylene film in acetonitrile (Scheme 1) and a thick poly(azobenzene) film in water. (Scheme 2) The solvolytic polymerization of PPBD with water is an unusual reaction which to the best of our knowledge has not been previously reported, although McCreery et al. have described the role of azo coupling in surface thin film growth while the DIAP procedure of Palacin et al. is similar in using a diazonium decomposition reaction to anchor a polymer film.