Eur. Phys. J. E 6, 109-115 (2001)

Counterion distribution in a spherical charged sparse brush

F. Muller¹, P. Fontaine², M. Delsanti³, L. Belloni³, J. Yang⁴, Y.J. Chen^{4, 5}, J.W. Mays⁴, P. Lesieur², 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  Laboratoire pour l'Utilisation du Rayonnement Electromagnétique, Centre Universitaire Paris-Sud, bât. 209D, BP 34, 91898 Orsay Cedex, France
³  Service de Chimie Moléculaire, CEA Saclay, F-91191 Gif-sur-Yvette Cedex, France
⁴  Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL 35294, USA
⁵  Exxon Chemical Co., Baytown, TX 77522, USA
⁶  Departments of Chemical Engineering and of Materials, University of California, Santa Barbara, CA 93106, USA

guenoun@drecam.saclay.cea.fr

(Received 14 February 2001 and Received in final form 2 May 2001)

Abstract
The counterion distribution within a spherical polyelectrolyte sparse brush was measured by small-angle X-ray scattering using contrast variation with different counterions by means of ion dialysis. The brush was made by self-association of charged diblock copolymers. Thanks to the contrast variation method, we were able to separate the signal due to the monomers and the signal due to the counterions. At a small length scale, it is demonstrated that the system behaves as independent charged rods whose counterion distribution follows the Poisson-Boltzmann model.

PACS
83.80.Uv - Block copolymers.
82.35.Rs - Polyelectrolytes.
61.10.Eq - X-ray scattering (including small-angle scattering).


© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001