Preparation and Characterization of Functional Compounds Encapsulated Microemulsion with Nonionic Surfactants

Influence of hydrophobic chain lengths of surfactant, co-surfactant, oil and different surfactant to co-surfactant ratios on phase behavior of Tween/alcohol/alkane/H2O was investigated with pseudo-ternary phase diagrams. The total areas of the microemulsion (ME) regions were determined. The largest ME region was formed when the ratio of surfactant: co-surfactant was 2 : 1 (w/w). The capacity for formation of MEs increased with an increase of hydrophobic chain length of the Tween, which was opposite to the trend for alkane (oil). N-butanol formed the largest ME region among the alcohols tested as co-surfactants. Sub-ME phases were identified by conductivity measurements. O/W MEs were observed when the water content was higher than 62 - 68%. The O/W sub-phase regions had significantly lower particle sizes and viscosities than either the W/O or bi-continuous sub-phases.