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Auto-assemblage de copolymères à blocs acryliques en milieu apolaire: un exemple de verre colloïdal attractif

Abstract : Gradient ABA copolymers dissolved in an apolar solvent that is selective for the end-blocks selfassemble into core-shell micelles. The micellar solutions constitute an exquisite system to study glass formation in colloidal suspensions in the presence of short-range attractive interactions. The structure and the dynamics at equilibrium and under flow are investigated as a function of temperature and concentration using small-angle X-ray scattering, rheology, and light scattering. At low concentrations, solutions behave like hard sphere suspensions; the variations of the low-shear viscosity over a wide range of concentrations and temperatures can be rescaled on a universal curve. At higher concentrations, short range attractive forces come into play, which strongly influence glass formation. The viscous phase is separated from the glass phase by a viscoelastic liquid phase, which spans over a wide range of volume fractions. This phase has many similarities with a weak gel but it instantaneously solidifies when it is sheared above a critical stress. Shear-induced gelation in attractive micellar solutions is markedly different from shear-thickening in conventional colloidal suspensions and in shake-gels. The glasses that form at higher concentrations can be attractive or repulsive depending of the strength of the short-range attractive interactions, which can be tuned by changing the temperature. Repulsive glasses exhibit slow dynamics and aging phenomena usually associated with glassy dynamics.
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Submitted on : Monday, December 14, 2009 - 8:00:00 AM
Last modification on : Wednesday, October 14, 2020 - 3:43:20 AM
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  • HAL Id : pastel-00005588, version 1

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Nathalie Merlet-Lacroix. Auto-assemblage de copolymères à blocs acryliques en milieu apolaire: un exemple de verre colloïdal attractif. Sciences de l'ingénieur [physics]. Université Pierre et Marie Curie - Paris VI, 2008. Français. ⟨pastel-00005588⟩

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