Cylindrical and Branched Micelles at Low Temperature: A Rheological Study

Abstract

We investigate the consequence of decreasing the temperature on the rheological behavior of the cylindrical and branched micelles of the ternary system of DDAB (dodecyldimethylammonium bromide)/STDC (sodium taurodeoxycholate)/water system. An isotropic cylindrical micelle-to-hexagonal liquid crystalline phase is optically (as a birefringence) and rheologically (gel like) detected on the STDC rich part at 6°C. On the other hand, branched micellar solution does not show any birefringence upon decreasing the temperature; however, it mainly exhibits disordered-ordered transition under shear. Such transition is more pronounced as the DDAB concentration increases as a consequence of the decrease in the curvature, and hence a sponge phase formation at low temperature.

Keywords:

• Bile salt
• branched micelles
• shear rheology
• surfactant solutions

Acknowledgments

This work was supported by MIUR (Ministero dell'Istruzione e dell'Università). PRIN-project 2006, “Biocompatible Soft Matter Made by Surfactants and Macromolecules.”

Notes

Current address for M. Youssry: Université de Bordeaux, IMS Laboratory, Talence, France.