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Silicone supramoléculaire : un nouveau concept permettant l'auto-cicatrisation

Abstract : Autonomous self-healable (without external stimulus) silicones exhibit too low mechanical properties restricting their use in industry. The aim of this study was to overcome this limitation. We focused our work on segmented PDMS-urea copolymers made of soft (SS) and hard segments (HS). First the investigation of the relationship between the bis-urea chemical structure and the macroscopic properties was made. Results shown that, the symmetry of HS governs materials rigidity. Moreover, with a too symmetrical HS, the material does not exhibit self-healing abilities. We have developed a new concept improving the healing efficiency of these materials. The idea was to add to the formulation of these silicone thermoplastics a macromolecular chain stopper. The new additive creates a defect in the supramolecular assembly which leads to smaller and more dynamic H-bonding clusters and hence a faster healing kinetic. Unlike plasticizers, this additive deteriorates the tensile modulus only marginally. We therefore report a stress at break recovery of 90% after 24 hours at room temperature for a PDMS-urea copolymer with a tensile modulus of 1MPa. The concept was also extented to a commercial thermoplastic (GENIOMER80). Finally, our last challenge was to manage the balance between rigidity and chains dynamics allowing self-healable materials with good mechanical properties. In this context we have synthesized new matrixes with higher HS percentage and additives with stickers with higher cohesive energy. These new syntheses have led to an improvement of the rigidity limit reachable by the autonomous self-healable silicones (3MPa).
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Léo Simonin. Silicone supramoléculaire : un nouveau concept permettant l'auto-cicatrisation. Matériaux. Sorbonne Université, 2018. Français. ⟨NNT : 2018SORUS149⟩. ⟨tel-02337508⟩

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