Abstract
The water in oil (W/O) emulsion is a crucial cosmetic base that makes oily constituents efficiently spread on the skin surface to provide high emollience, high SPF and other features. Despite the functionality that they offer, W/O emulsions require technical improvement. The conventional W/O emulsifiers, which stabilize the W/O emulsion at the oil-water interface, tend to be dissolved as a mono-dispersed molecule in oil bulk due to the lack of lipophobicity, resulting in inefficient stabilization. For that reason, the W/O emulsion requires a considerable amount of W/O emulsifier as well as gelling agents that add undesirable sticky and greasy textures to the finished product. In the present study, we focused on amphiphiles with multiple hydroxyl groups that should render temperature insensitive large lipophobicity to the molecule. As a result, it was found that hyper internal phase W/O emulsions can be prepared with phytantriol (3, 7, 11, 15 - tetramethyl- 1, 2, 3 -hexadecanetriol) as an emulsifier. The emulsion showed excellent stability in spite of containing 97% aqueous substances with various oils such as non-polar, polar, and silicone oils. Innovative basic research findings regarding high internal phase O/W or W/O emulsions have been reported ; however, these emulsions are unsuitable for practical use due to insufficient stability derived from temperature-sensitive lipophobicity. Phytantriol is known to form an anomalous bicontinuous cubic liquid crystalline phase with water. To gain insight into the emulsification mechanism, extensive research has been conducted on the phase behavior of phytantriol in the presence of oil and water. Consequently, the emulsification mechanism of the present emulsion was revealed. Additionally, it was found that the present emulsion left a thin liquid crystalline film extended on the skin surface following evaporation of the solvents upon application. This technology provides important functionalities to emulsions such as high emollient effect and occlusive effect, as well as a preferable non-sticky, non-greasy texture, unobtainable through conventional technologies.
