Effect of salinity on the ultrasonic absorption and flow birefringence of microemulsions

E. Hirsch , F. Debeauvais , F. Candau , Jérôme Lang , R. Zana

The behaviour of microemulsions made of toluene, brine, sodium dodecylsulfate and butanol has been investigated as a function of salinity by means of ultrasonic absorption and flow birefringence techniques. As the salinity is increased in the system, phase transitions from Winsor I → Winsor III and Winsor III → Winsor II occur at S1 = 5.5 and S2 = 8 g NaCl/100 g water respectively. At both S1 and S2 salinities, the flow birefringence exhibits a divergence which demonstrates the existence of a large orientational order in/or between microemulsion droplets. Anomalous absorption effects occur only in the vicinity of S2 for which critical behaviour of the elastic and quasi-elastic light-scattering and percolation of electrical conductivity have been observed. These effects have been attributed to a coupling between the sound waves and the droplet merging-breakdown equilibria. In the range between S1 and S2 both flow birefringence and ultrasonic absorption data suggest a peculiar structure of the middle phase microemulsion.

Mots clés: electrical conductivity of electrolytic liquids; emulsions; flow birefringence; light scattering; molecular orientation; phase equilibrium; ultrasonic absorption

Domaines: Articles anciens

E. Hirsch, F. Debeauvais, F. Candau, Jérôme Lang, R. Zana. Effect of salinity on the ultrasonic absorption and flow birefringence of microemulsions. Journal de Physique, 1984, 45 (2), pp.257-263. ⟨10.1051/jphys:01984004502025700⟩. ⟨jpa-00209751⟩