Superswollen Microemulsions Stabilized by Shear and Trapped by a Temperature Quench
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We studied the solubilization of oil in the C16E8/hexadecane/H2O system. Close to the phase inversion temperature (PIT), the system, at equilibrium, can form either homogeneous states (i.e., microemulsions) at high surfactant concentrations or three-phase states at lower concentrations. We show that, under gentle shear, at a line we named the clearing boundary (CB), located a few degrees below the PIT, the system is homogeneous regardless of the surfactant concentration. We relate this shift of the microemulsion boundary to shear-induced disruption of the asymmetric bicontinuous structure. Although this state quickly relaxes to equilibrium when shear is stopped, we show that is still possible to trap it into a metastable state through a temperature quench. This method is the sub-PIT emulsification that we described in a previous work (Roger et al. Langmuir 2010, 26, 3860-3867).