Eur. Phys. J. E (2015) 38: 52
https://doi.org/10.1140/epje/i2015-15052-1

Regular Article

Effect of charge polydispersity and charge residence time on the dynamics of a micellar system

¹ Laboratoire de Physique théorique et appliquée, Université Sidi Mohamed Ben Abdellah, Faculté des Sciences, Dhar El Mahraz, BP 1796 Fes, Atlas, Morocco
² Laboratoire Charles Coulomb (L2C), UMR 5221 CNRS-Université de Montpellier, Montpellier, F-France

^* e-mail: luca.cipelletti@univ-montp2.fr

Received: 13 February 2015
Revised: 3 April 2015
Accepted: 16 April 2015
Published online: 16 June 2015

Abstract

We use dynamic light scattering to investigate the effects of charge polydispersity and charge residence time on the dynamics of a micellar system. While in the corresponding uncharged system only one exponential relaxation is observed, two relaxation modes are seen when charging the micelles by adding charged co-surfactant molecules with a long residence time. We attribute the existence of these two relaxation modes to the combined effect of size polydispersity and charge polydispersity, i.e. frozen fluctuations of the number of charges per micelle. Further support to this scenario is provided by control experiments on a similar charged system, but where the charge residence time is short compared to the time scales probed by dynamic light scattering. Here, charge polydispersity is effectively suppressed due to the rapid exchange of charged molecules between micelles and only one single relaxation mode is seen, thereby demonstrating the key role of frozen charge fluctuations in the complex dynamics of our micellar system.