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Interaction et structure de copolymères neutres-chargés dissymétriques en solution aqueuse

Abstract : In a selective solvent such as water, neutral-charged diblock copolymers exhibit a variety of different self-assembled structures such as spheres, cylinders or bilayers. Asymmetric fully charged- neutral diblock copolymers made of a long and fully charged moiety (polyelectrolyte) and of a short neutral moiety (hydrophobic) are expected to form spherical micelles in water, composed of a small dense core (association of the neutral blocks) where the polyelectrolyte blocks emerge forming a large spherical charged corona (spherical polyelectrolyte brush). The structure and the interactions of such spherical micelles are investigated in a large range of copolymer concentrations C (from dilute to concentrated regime) and as a function of the added salt concentration Cs. Using light scattering and small angle neutron scattering, it is shown the influence of C and Cs on the micelle structure (core shape, number of chains per micelle and conformation of the polyelectrolyte blocks). In particular, it is demonstrated that the charged corona has a very extended conformation (urchin-like) in dilute regime both by the average density profile and the fluctuating profile (local statistics). Moreover, a liquid-like order (electrostatic and packing interactions between the micelles) is observed from dilute to concentrated regime. However, in concentrated regime, polyelectrolyte correlations appear at small spatial scales and coexist with the previous order. The counterion distribution within the corona is checked by small angle x-ray scattering using contrast variation method (different counterions by means of ion dialysis). In the case of sparse coronae (low aggregation number) it is demonstrated that the system behaves as independent charged rods whose counterion distribution follows the Poisson-Boltzmann model. The case of denser coronae is also discussed. Finally, we have studied the critical micellar concentration of the copolymers by capillary electrophoresis as a new and effective tool. Such experiments raise the question about the equilibrium of self-assembled neutral-charged diblock copolymer solutions.
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https://tel.archives-ouvertes.fr/tel-00001847
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Submitted on : Monday, October 21, 2002 - 4:03:57 PM
Last modification on : Wednesday, September 12, 2018 - 2:14:13 PM
Long-term archiving on: : Friday, April 2, 2010 - 8:01:23 PM

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  • HAL Id : tel-00001847, version 1

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François Muller. Interaction et structure de copolymères neutres-chargés dissymétriques en solution aqueuse. Analyse de données, Statistiques et Probabilités [physics.data-an]. Université de la Rochelle, 2000. Français. ⟨tel-00001847⟩

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