Eur. Phys. J. B 3, 59-72 (1998)
https://doi.org/10.1007/s100510050284

Identification of flow mechanisms for a soft crystal

¹ Groupe Dynamique des Phases Condensées, Unité Mixte de Recherche CNRS/Université Montpellier II n° 5581, 34095 Montpellier Cedex 05, France
² Groupe Dynamique des Phases Condensées, Unité Mixte de Recherche CNRS/Université Montpellier II n° 5581, 34095 Montpellier Cedex 05, France European Synchrotron Facility, BP 220, 38043 Grenoble, France Institut Laue Langevin, BP 156, 38043 Grenoble, France

Corresponding authors: ^a molino@gdpc.univ-montp2.fr - ^b porte@gdpc.univ-montp2.fr

Received: 7 July 1997
Revised: 16 January 1998
Accepted: 5 March 1998
Published online: 15 May 1998

Abstract

We study the behavior under flow of soft spherical micelles forming a fcc phase at high volume fraction. Due to the size (300 Å) of the elementary objects, the structure can be investigated through X-rays and neutron scattering, at rest and under flow in a Couette cell. Using scattering in two perpendicular directions, different mechanisms of flow are identified. At intermediate shear (around 100 s^-1) the system exhibits the so called layer sliding mechanism where two dimensional hexagonal compact planes of spheres align themselves with the Couette cell walls. At lower shear rate, the fcc structure is locally preserved, and the flow is mediated by defects between crystallites. At high shear rate, we observe the melting of the structure and a liquid-like structure factor. Moreover, we were able to use the existence of the layer sliding regime to generate a fcc monocrystal by annealing the satcking faults between the decorrelated planes created by the layer sliding.