Eur. Phys. J. E 3, 45-53 (2000)
DOI: 10.1007/s101890070040

Ordering of urchin-like charged copolymer micelles: Electrostatic, packing and polyelectrolyte correlations

F. Muller¹, M. Delsanti², L. Auvray³, J. Yang⁴, Y.J. Chen⁴, J.W. Mays⁴, B. Demé⁵, M. Tirrell⁶ and P. Guenoun<sup>1

1</sup>  Service de Physique de l'Etat Condensé, CEA Saclay, F-91191 Gif-sur-Yvette Cedex, France
²  Service de Chimie Moléculaire, CEA Saclay, F-91191 Gif-sur-Yvette Cedex, France
³  Laboratoire Léon Brillouin, CEA Saclay, F-91191 Gif-sur-Yvette Cedex, France
⁴  Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL 35294, USA
⁵  Institut Laue-Langevin, BP 156, F-38042 Grenoble Cedex, France
⁶  Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA

muller@spec.saclay.cea.fr
guenoun@spec.saclay.cea.fr

(Received 8 October 1999)

Abstract
We report the results of small-angle neutron scattering (SANS) studies on aqueous solutions of spherical polyelectrolyte micelles formed by association of charged-neutral diblock copolymers. The neutral moieties are found to self-assemble into small dense spheres (cores of the micelles) whose sizes are independent of the polymer concentration c. In the dilute regime, c<c^*, where c^* is the overlap concentration of the micelles, the conformation of the charged groups, which form the corona of the micelles, is found to be extended. A liquid-like order is observed over a wide concentration range spanning from the dilute regime to the concentrated regime. For c>c^*, polyelectrolyte correlations appear at smaller spatial scales and coexist with the liquid-like order. These results suggest that for dense brushes, above c^*, the rod-like statistics of the charged chains begin to disappear due to contraction of corona arms or by interpenetration of coronae. For less dense brushes, the charged chains are found to be extended up to concentrations far above c^*, before the progressive development of polyelectrolyte correlations.

PACS
61.25.Hq - Macromolecular and polymer solutions; polymer melts; swelling.
83.70.Hq - Heterogeneous liquids: suspensions, dispersions, emulsions, pastes, slurries, foams, block copolymers, etc..
82.70.Dd - Colloids.

© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2000