Ordering Phenomena in Surfactant Systems: From Micellar Solutions to Gel and Crystalline Phases

摘要

The phase behavior of surfactant systems is investigated using alkyltrimethylammonium bromide surfactants with different alkyl chain lengths (dodecyl-, tetradecyl-, hexadecyl- and octadecyl) as model substances. The transitions between micellar solution, gel-phase and crystalline phase are characterized by the combination of Raman spectroscopy and small angle neutron scattering. It is demonstrated that in systems with small surfactant molecules the aqueous solution crystallizes directly on cooling to form hydrated crystals while an intermediate gel phase is observed in long chain systems. The cross-over is found for the hexadecyl- compound where the gel phase appears only at high concentrations.