In electrochemical surface grafting of bisdiazonium salts, it is has generally been found that the resulting thin films are polymeric and composed of a variety of chemical linkages including azo-coupled units and bonds formed by direct arylation of an aromatic ring by an aryl radical. In the present study, we see a distinctly different pattern of reactivity on oxide surfaces as opposed to glassy carbon and gold. The latter substrates, which have both been demonstrated to directly react with aryl diazonium groups, are rapidly coated by PPBD as measured by ferrocene grafting and voltammetry (Figures and) giving a diazonium-bearing thin film which is strongly bound to the substrate. This process likely takes place through radical arylation steps to yield a phenylene film bound through a direct Ar-surface bond as represented in Scheme 1.