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Élastomères siloxanes à liens dynamiques

Abstract : The polysiloxane elastomers are thermosets, chemically cross-linked, that can neither be reshaped, transferred on a support different from their original one nor recyclable. In order to overcome these limitations, siloxane elastomer vitrimers have been developed, the vitrimers being materials able to be reshaped, repaired and welded thanks to catalyzed and thermo-activated associative exchange reactions occurring within the network. In a first approach, we studied the trans-siloxanation, the intrinsic exchange reaction of living siloxanes, catalyzed by the silanolate anion SiO-. Nevertheless, this living nature leads to equilibrium between the network and cycles, that can evaporate upon heating and cause the depolymerisation of the network by intramolecular trans-siloxanation. The living elastomers are thus not vitrimer since their connectivity is continuously modified. However, we have shown that the addition of caesium carbonate accelerates the exchange reaction and allows the welding of two joints with at least one living. In the second approach, the vitrimer behaviour relies on imine dynamic bonds introduced into a non living network (no silanolate anion). As this bond is exchangeable but also dissociable under soft conditions, imine siloxane elastomers can not only be reshaped and but also recycled. Finally, the introduction of silica charges improves the mechanical properties without altering the vitrimer properties.
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Submitted on : Saturday, November 10, 2018 - 1:02:22 AM
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  • HAL Id : tel-01918184, version 1

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Fanny Angot. Élastomères siloxanes à liens dynamiques. Chimie-Physique [physics.chem-ph]. Université Pierre et Marie Curie - Paris VI, 2016. Français. ⟨NNT : 2016PA066699⟩. ⟨tel-01918184⟩

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