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Theses

Bioinspired photonic cellulose films

Abstract : Cellulose nanocrystals are bio-sourced rod-like nanoparticles showing a remarkable iridescent optical response owing to their ability to self-assemble into cholesteric liquid crystalline phases above a threshold concentration. In the literature, 100% cellulose films and composite materials capable of impressive colour responses have been prepared respectively from aqueous suspensions by controlled drying and/or using organic and inorganic precursors. In this PhD work, we prepare materials from polymerisable cholesteric suspensions with the aim of developing a photonic optical response for arange of composite materials, including flexible and stimulable ones. In that extent, cellulose nanocrystals are compatibilised with organic apolar solvents and monomers using the steric stabilisation of a surfactant. The modification of colloidal interactions in apolar suspensions reduces the cholesteric pitch compared to aqueous suspensions, leading to an optical response at high angles of incidence already in suspension. The optical response in suspension is tuned by the control of the orientation of the cholesteric helices by electric (reorientation and unwinding) and magnetic (alignment) fields before being locked into polymer composites. The retention of the cholesteric assembly of fillers and their field-aligned orientation preserves an iridescent optical response in the composites that is characterised in detail by angular-resolved spectroscopy. In a complementary approach, cellulose and composite films are prepared by drying an organic solvent CNC suspension to yield a slight iridescent optical response in reflection at normal incidence.
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https://tel.archives-ouvertes.fr/tel-03484314
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Submitted on : Friday, December 17, 2021 - 1:02:15 AM
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Axel Fouques. Bioinspired photonic cellulose films. Polymers. Université Grenoble Alpes [2020-..], 2020. English. ⟨NNT : 2020GRALV044⟩. ⟨tel-03484314⟩

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