CH-π Interactions as the Driving Force for Silicone-Based Nanocomposites with Exceptional Properties†

Among the various issues pertaining to the use of composite polymeric materials based on nanoparticles, the dispersion of the nanofillers in the matrix and the nature of the fillerpolymer interface are central. In many cases, poor dispersion results in agglomeration or phase separation, leading to a dramatic loss of the materials properties. To overcome this problem, a number of strategies have been developed with various degrees of success. They usually come at a high price, due to the necessity of modifying the surface state of the filler. Here, we report on novel carbon nanotubes-reinforced poly(dimethyl)siloxane nanocomposites and surprisingly, for which the use of “self pure” multiwall carbon nanotubes, i.e., without any surface functionalization or specific surface treatment, turns out to be the most efficient approach to impart new key-properties to the silicone matrix. Viscometric, rheological and theoretical studies have been performed that demonstrate the remarkable potential of dispersing a very tiny amount of “self pure” carbon nanotubes in silicone, paving the way to unexpected applications, e.g., in the field of fire endurance. Very interestingly, only tiny amounts of MWCNTs are required: usually less than 0.5 wt %. Those properties all rely on the nature of the nanotube-silicone interface interactions, which are dominated by additive CH-p interactions between the methyl groups of the polymer and the nanotube surface. Polydimethylsiloxane (PDMS) is the most common silicone elastomer owing to its ease of fabrication and advantageous chemical/physical properties, such as low surface energy, low glass transition temperature and high chain mobility. [1] Currently, to compensate for their poor mechanical properties, silicone materials have to be reinforced by incorporation of particulate materials, silica being the most commonly used filler. To date, the in situ filling process, where silica is generated into the elastomeric matrix, is the most efficient way to fill PDMS materials. [2] However, this reinforcement still re