Development of Novel Multifunctional Cosmetic Raw Materials and Their Applications. II.^† Novel Emulsifying Method with Random Copolymer of Polyoxyethylene / Polyoxypropylene

Abstract

New multifunctional raw materials for cosmetics, polyoxyethylene (POE) /polyoxypropylene (POP) dimethylether [EPDME] were previously developed by the authors. The present study presents a novel emulsifying method by which ultrafine emulsions of particle size less than 100 nm can be easily prepared using EPDME. The equilibrium phase state of the water - oil - surfactant - EPDME was examinated using a phase diagram so as to clarify the underlying mechanism in the preparation of ultrafine emulsions and the results indicated the following: [1] a special microemulsion phase is formed in a region different from that of the normal microemulsion phase when oil, EPDME, surfactant and water are mixed in the proper proportions and [2] ultrafine emulsions form in a two-phase region (O + Wm) when the composite of the microemulsion phase is diluted with water. The chemical structure of EPDME is similar to that of the polyoxyethylene chain in polyoxyethylene nonionic surfactants. EPDME may thus be considered a hydrophilic co-surfactant and a special microemulsion phase is formed at high EPDME and polyoxyethylene nonionic surfactant. EPDME may possibly be distributed in the polyoxyethylene chain of the polyoxyethylene surfactant. When diluting this microemulsion phase, EPDME rapidly decreases in concentration and, in free form virtually unadsorbed onto the oil - water interface may diffuse in the bulk water phase from polyoxyethylene chains in surfactants. It would then follow that an ultrafine emulsion consisting only of nonionic surfactant and oil may form in excess.