Alpha-tocopherol in CTAB/NaCl systems - The light scattering studies

The light scattering techniques - laser Doppler electrophoresis (LDE) and dynamic light scattering method (DLS) - were applied to characterize properties of the cetyltrimethylammonium bromide (CTAB) micellar solutions in the presence of α-tocopherol (vitamin E) and NaCl at 25 °C. The surfactant concentration changed from 2 mM to 25 mM and the molar ratio of vitamin E to CTAB was in the range 0.01-0.18. It was found that the incorporation of α-tocopherol molecules into the palisade layer of CTAB micelles increases the ionization degree of mixed aggregates even at 0.5 M NaCl. At the same time it does not cause a significant increase of the mixed micelle sizes (the number of CTAB molecules in the aggregates). The observed increase of surface electrical charge of micelles in the presence of vitamin E leads to an increase of their electrophoretic mobility. A small size of the mixed micelles (about 5.0 and 6.0 nm at 0.15 and 0.50 M NaCl, respectively) points at full solubilisation of the active substance. This effect can be useful for elaboration of bioactive substance carriers in the micellar systems in the presence of electrolyte.