Flexible paper@carbon nanotube@polypyrrole composites: The combined pivotal roles of diazonium chemistry and sonochemical polymerization

Cellulosic paper has drawn much attention in the recent years owing to its availability and remarkable physicochemical and mechanical properties that make it ideal support for new technologies. Combining cellulosic paper and conductive materials such as inherently conductive polymers and/or carbon nanotubes not only contributes to the composite science and technology sector but also to the development of new electronic applications. In this context, we have investigated new surface and interface chemical and sonochemical strategies in view of preparing robust conductive, electrochemical active paper sheets by sequential deposition of diazonium-modified multiwalled carbon nanotubes (CNTs) and in situ sonochemical synthesis of polypyrrole. Towards this end, CNTs were modified with amino-and sulfonatebenzenediazonium salts via in situ diazonium generation process in HBF4 acid aqueous solution. The diazonium functionalization helped to easily disperse the CNTs in water and on the paper surface to provide a platform for sonochemical (US) synthesis of polypyrrole. The functionalized CNTs were characterized by Raman, XPS and SEM. The 1 h sonochemical film synthesis provided the best electrochemical behavior compared to the traditional chemical (Ch) route. The SEM analysis of the Paper@CNT@PPy, showed that the CNTs were coated uniformely with PPy forming a network of thicker core/shell CNT/polypyrrole nancomposite wires. Polypyrrole small particles topping the CNT/PPy-coated paper are densely packed and evenly distributed on the paper. These characteristics control the final physicochemical properties of the composite paper electrodes.