Emulsifying potency of new amino acid-type surfactant (II): Stable water-in-oil (W/O) emulsions containing 85 wt% inner water phase

The ternary phase diagram for N-[3-lauryloxy-2-hydroxypropyl]-L-arginine L- glutamate (C12HEA-Glu), a new amino acid-type surfactant, /oleic acid (OA)/ water system was established. The liquid crystal and gel complex formations between C12HEA-Glu and OA were applied to a preparation of water-in-oil (W /O) emulsions. Stable W/O emulsions containing liquid paraffin (LP) as the oil and a mixture of C12HEA-Glu and OA as the emulsifier were formed. The p reparation of stable W/O emulsions containing 85 wt% water phase was also p ossible, in which water droplets would be polygonally transformed and close ly packed, since the maximum percentage of inner phase is 74% assuming unif ormly spherical droplets. Water droplets would be taken into the liquid cry stalline phase (or the gel complex) and the immovable water droplets would stabilize the W/O emulsion system. The viscosity of emulsions abruptly incr eased above the 75 wt% water phase (dispersed phase). The stability of W/O emulsions with a lower weight ratio of OA to C12HEA-Glu and a higher ratio of water phase was greater. This unusual phenomenon may be related to the f ormation of a liquid crystalline phase between C12HEA-Glu and OA, and the s tability of the liquid crystal at a lower ratio of oil (continuous phase). W/O and oil-in-water (O/W) emulsions containing LP were selectively prepare d using a mixture of C12HEA-Glu and OA since the desirable hydrophile-lipop hile balance (HLB) number for the emulsification was obtainable by mixing t he two emulsifiers.