Effect of α-tocopherol on the properties of microemulsions stabilized by the ionic surfactants

The properties of oil-in-water (o/w), bicontinuous (bc) and water-in-oil (w/o) microemulsions which were formed by the anionic (sodium dodecyl sulfate - SDS) and cationic (cetyltrimethylammonium bromide - CTAB) surfactants were investigated at the α-tocopherol (vitamin E) concentration ranging from 0.01 to 0.25 wt%. Hydrodynamic diameter increased in the o/w systems and decreased in the w/o systems with the increasing content of alcohol. Generally, the CTAB aggregates were bigger than those of SDS. The microemulsions stabilized by the cationic surfactant were more polydispersive than those stabilized by the anionic one. The concentration of the alcohol affected the values of electrolytic conductivity as well as the electrophoretic mobility. The addition of vitamin E to the microemulsions slightly influenced their properties. The effect of α-tocopherol was the most significant for the systems having a low content of alcohol as a co-surfactant. Thus, the presence of vitamin E raised the electrophoretic mobility of the microemulsion droplets. This effect was stronger in the microemulsion stabilized by SDS.