Abstract

Inverse water–in–oil microemulsions are suspensions of spherical droplets of water coated by a monolayer of surfactant molecules, immersed in oil. We have studied WAD (water/AOT/decane, where AOT denotes sodium–bis–di–ethyl–sulfosuccinate) microemulsions far from critical points and near the percolative transition from electrically insulating to electrically conducting. The AOT molecules have a bulky tail and a small head so that the coating film has a spontaneous curvature toward water. Owing to this reason, water droplets are quite stable and, from 10 to 50°C, a large one– phase region, called L₂ phase extends in the ternary phase triangle from the decane corner into the middle of the phase diagram. A percolation line is found in this region. We have observed optical nonlinearity near the percolation line and far from the one–phase two– phase boundary line. In this point, the material turbidity is very low and the material appears to be suitable for several nonlinear optical devices.

© 2003 Optical Society of America