Titre de la dissertation: »Tailoring of novel benzoxazine-based elastomeric matrices incorporating carbon nanotubes for innovative broad-range piezoresistive pressure sensors »

Promoteur: Monsieur David Beljonne et Leila Bonnaud

Résumé de la dissertation: Flexible and stretchable pressure sensors are gaining growing attention in numerous applications, namely in robotic artificial intelligence, personal electronic devices and industrial production. The development of such devices and, in particular, of electronic skin, is key to the interfacing between human bodies and the outside world. To mimic the tactile sensing properties of natural skin, one should develop large arrays of sensing elements, each one acting as an independent pressure detector supported on a flexible and stretchable substrate. In this context, there is an increasing demand for the development of innovative materials with electro-responsive and elastomeric behavior. In this work, the potential of benzoxazine networks as the central platform for the matrix formulation was investigated.Polybenzoxazines are an important class of phenolic resins. They are attracting much attention and interest from both academic and industrial research groups because they simultaneously combine the easy handling and processing of epoxy resins with the high thermal resistance of bis-maleimide and phenolic resins. Despite its interesting features, benzoxazine chemistry has been almost exclusively dedicated to the preparation of thermoset materials with the widest possible glassy zone, leading to brittle materials. While some studies have focused on the development of benzoxazine resins with combined flexibility, ductility, and high glass transition temperature (Tg), not much effort has been reported yet on the use of a benzoxazine motif to prepare elastomers. Indeed, elastomers are generally used to bring high flexibility and stretchability to pressure sensors. The work presented in this thesis is part of a large-scale effort to develop an innovative generation of patterned coatings based on benzoxazine matrices incorporating electrically conductive 2D layers for wide-range pressure sensing applications. Two approaches have been followed. First, we report on the design of novel trifunctional benzoxazine precursors based on tris(3-aminopropyl)amine and phenol reagents. These precursors have been successfully synthesized and copolymerized with polyetheramines of different lengths to tune the thermomechanical properties of the resulting networks. Second, new benzoxazine precursors based on amine-terminated PDMS polymers were also synthesized and evaluated. These benzoxazine systems were then filled with multi-walled carbon nanotubes in order to turn them into electrically-conductive thermoset elastomeric resins. The resulting networks exhibit high sensitivity to pressure by transducing the resistance change of the device into an electrical signal when applying external force (piezo-resistivity). Overall, this thesis highlights the advantages of employing benzoxazine resins combined with carbon nanotubes to achieve efficient and high-sensitivity piezo-resistive pressure sensors.