Mechanical properties of carbon nanotube-PMMA based hybrid coatings: the importance of surface chemistry

The poor miscibility of carbon nanotubes (CNTs) in common organic solvents and organic monomers requires their modification by suitable functional (reactive or not) groups prior to their incorporation in thermoplastic polymers. We studied the influence of the functionalization of the surface of CNTs on their miscibility in poly(methyl methacrylate), following two main strategies: (i) the covalent grafting of hydrolyzable Si(OEt)(3) groups on oxidized CNTs and (ii) the non-covalent adsorption of a polycation on pristine CNTs, allowing for further reactions by the sol-gel process. The mechanical properties of CNT/polymer-based nanocomposite thin films were studied using the nanoindentation technique. The hardness and the elastic indentation modulus were found to improve using modified CNTs, with more sensitivity observed on the elastic response.