Percolation transition in water–AOT–decane microemulsion investigated by transient grating measurement

Abstract

We report results from a heterodyne-detected transient grating experiment on a three-component microemulsion system, consisting of water–AOT–decane. We studied the microemulsion characterized by a water-to-AOT ratio of X=40.8 and a volume fraction φ =0.50, in a temperature range around the percolation threshold. The measurements have been performed with two exchanged momenta q≈ 1 and 2μ m⁻¹, corresponding to sound frequencies around 200 and 420 MHz. The measured sound velocities show small but significant evidence of the percolation transition in the temperature domain.

Acknowledgments

The research has been performed at LENS. We thank Riccardo Ballerini for the accurate mechanical realizations, and Mauro Giuntini and Marco De Pas for providing their continuous assistance in the set-up of the electronics. We thank P. Baglioni and M. Ambrosi for AOT purification. This work was also supported by EC grant N.RII3-CT-2003-506350, by CRS-INFM-Soft Matter (CNR) and by MIUR-COFIN-2005 grant N. 2005023141-003.