Slow relaxation mode in concentrated oil-in-water microemulsions consisting of repulsive droplets.

Yoshiyuki Hattori (1) , Hideharu Ushiki (2) , Laurent Courbin (3) , Pascal Panizza (4)

1 Graduate School of Bio-applications and Systems Engineering
2 Faculty of Agriculture
3 SEAS - Harvard John A. Paulson School of Engineering and Applied Sciences
4 GMCM - Groupe matière condensée et matériaux

The present contribution reports on the observation of two diffusive relaxation modes in a concentrated microemulsion made of repulsive droplets. These two modes can be interpreted in the frame of Weissman's and Pusey's theoretical pioneering works. The fast mode is associated to the collective diffusion of droplets whereas the slow one corresponds to the relaxation of droplet concentration fluctuations associated with composition and/or size. We show that (i) repulsive interactions considerably slow down the latter and (ii) a generalized Stokes Einstein relationship between its coefficient of diffusion and the Newtonian viscosity of the solutions, similar to the Walden's rule for electrolytes, holds for concentrated microemulsion systems made of repulsive droplets.

Keywords: Structure of liquids; Diffusion and ionic conduction in liquids; Disperse systems; complex fluids

Domains: Materials Science [cond-mat.mtrl-sci]; Biophysics

Yoshiyuki Hattori, Hideharu Ushiki, Laurent Courbin, Pascal Panizza. Slow relaxation mode in concentrated oil-in-water microemulsions consisting of repulsive droplets.. Physical Review E : Statistical, Nonlinear, and Soft Matter Physics, 2007, 75 (2 Pt 1), pp.021504. ⟨10.1103/PHYSREVE.75.021504⟩. ⟨hal-00907961⟩