Formation of polyphenylene films on metal electrodes by electrochemical reduction of benzenediazonium salts

It is possible to form micrometer thick polyphenylene (PP) films by electrochemical reduction of benzenediazonium tetrafluoroborate on metals in acetonitrile. The electrochemical behavior of the PP film is characterized by different electrochemical transient methods and is surprisingly different from that observed with other diazonium salts. The films are analyzed by IR and time-of-flight secondary ion mass spectroscopies; their thickness and conductivity are also characterized. Because they are conductive, these micrometer thick films can be further derivatized by electrochemical reduction of other diazonium salts, for example, nitrophenyl or bromophenyl diazonium salts. Copper can also be deposited on the top of the PP film. The behavior of redox probes on PP films is discussed as well as the origin of this increased conductivity. A simple model for the reaction kinetics of electrografting is presented.