OIL-IN-WATER MICROEMULSIONS FROM ASSOCIATION STRUCTURES OF SURFACTANT, WATER AND AMINOSILICONE POLYMER OIL

The interaction of an aminosilicone polymer oil, a nonionic surfactant and water was examined by ternary phase diagram, spinning drop interf acial tension and particle size measurement of oil-in-water microemuls ions resulting from a unique patented procedure to combine isotropic t ernary mixtures with additional water. Transitory very low interfacial tensions against water were observed for mixtures along the aminosili cone-surfactant edge of the phase diagram. Inclusion of sufficient wat er in these mixtures produced clear compositions located in an isotrop ic region. It is believed that the isotropic region is an association complex, possibly inverse micellar, involving hydrogen bonding between water, ether oxygen atoms of the nonionic surfactant and amino groups of the aminosilicone polymer. Oil-surfactant-water compositions in th is isotropic region result in ultra-low interfacial tensions against w ater that pass through a minimum value with time, are at least an orde r of magnitude lower (< 0.0001 mN m(-1)) than without associated water , and occur in a shorter period of time. The interfacial tensions of i sotropic compositions that contain sufficient surfactant to stabilize a microemulsion could not be measured but are believed to be even lowe r and reached more rapidly. Surprisingly, compositions in this isotrop ic region yield silicone-in-water microemulsions on instantaneous dilu tion toward the water corner of the phase diagram. Gradual dilution of compositions in the isotropic region with water failed to produce suc h microemulsions and instead yielded opaque two or more phase mixtures . Oil-in-water microemulsions were easily made by quickly shaking an i sotropic mixture in water to achieve mixing. By this technique, it is believed that mixing to disperse the aminosilicone polymer in the dilu tion water occurs in the same time period when ultra-low interfacial t ensions are present. (In contrast, gradual dilution with water slowly changed the mixture composition until it was out of the isotropic regi on and entered a two-phase region where an opaque emulsion of much lar ger particle size formed.) Microemulsions with aminosilicone oil conce ntrations of 5, 10, 20, 30 and 40% were produced from the same isotrop ic mixture with essentially no variation in the particle size produced . The microemulsions made by this technique appear to be kinetically s table, remaining unchanged in particle size for years. They may be fur ther diluted with water without any change in particle size and can be used in formulations much as with standard emulsions. (C) 1998 Elsevi er Science B.V.