Development of Novel Cosmetic Base Using Sterol Surfactant. II. Solubilizing of Sparingly Soluble Ultraviolet Ray Absorbers

The study explored the use of sterol surfactants, which have a bulky planar structure, to solubilize sparingly soluble ultraviolet ray absorbers effectively. It was found that these surfactants could create a unique microemulsion different from other surfactants, featuring a rigid core with solubilized compounds between hydrophobic moieties, surrounded by a polyoxyethylene chain to prevent self-aggregation. NMR analysis indicated that a polyoxyethylene/polyoxypropylene random copolymer dimethyl ether fit into narrow gaps between the surfactant's hydrophobic moieties, enhancing the solubilization of ultraviolet ray absorbers.