DOI: 10.1209/epl/i2001-00359-2


Europhys. Lett., 55 (6) , pp. 887-893 (2001)

Ring-driven shear thickening in wormlike micelles?

M. E. Cates¹ and S. J. Candau<sup>2

1</sup>  Department of Physics and Astronomy, University of Edinburgh, Kings Buildings Mayfield Road, Edinburgh EH9 3JZ, Scotland, UK
²  Laboratoire de Dynamiques des Fluides Complexes, UMR7506 Université Louis Pasteur - 4 rue Blaise Pascal, F-67070 Strasbourg, France

(Received 11 May 2001; accepted in final form 6 July 2001)

Abstract
The shear-thickening behaviour of wormlike micelles, at concentrations just below "overlap" , remains unexplained. In some cases, it has recently been confirmed that very slow relaxations must be present even in the quiescent state -for example, the shear-thickening properties can depend on earlier thermal cycling. We present a speculative scenario based on the presence, just below the (apparent) overlap threshold, of large rings whose linking and delinking kinetics control the shear-thickening process. Equilibration between rings and open chains in turn controls the slow relaxations.

PACS
82.70.Uv - Surfactants, micellar solutions, vesicles, lamellae, amphiphilic systems (hydrophilic and hydrophobic systems).
83.60.Pq - Time-dependent structure (thixotropy, rheopexy).
83.10.Tv - Structural and phase changes.


© EDP Sciences 2001