Ronald Paul Gee

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 interfacial tension and particle size measurement of oil-in-water microemulsions resulting from a unique patented procedure to combine isotropic ternary mixtures with additional water. Transitory very low interfacial tensions against water were observed for mixtures along the aminosilicone-surfactant edge of the phase diagram. Inclusion of sufficient water in these mixtures produced clear compositions located in an isotropic 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 this isotropic region result in ultra-low interfacial tensions against water that pass through a minimum value with time, are at least an order of magnitude lower (<0.0001 mN m−1) than without associated water, and occur in a shorter period of time. The interfacial tensions of isotropic compositions that contain sufficient surfactant to stabilize a microemulsion could not be measured but are believed to be even lower and reached more rapidly. Surprisingly, compositions in this isotropic region yield silicone-in-water microemulsions on instantaneous dilution toward the water corner of the phase diagram. Gradual dilution of compositions in the isotropic region with water failed to produce such microemulsions and instead yielded opaque two or more phase mixtures. Oil-in-water microemulsions were easily made by quickly shaking an isotropic mixture in water to achieve mixing. By this technique, it is believed that mixing to disperse the aminosilicone polymer in the dilution water occurs in the same time period when ultra-low interfacial tensions are present. (In contrast, gradual dilution with water slowly changed the mixture composition until it was out of the isotropic region and entered a two-phase region where an opaque emulsion of much larger particle size formed.) Microemulsions with aminosilicone oil concentrations of 5, 10, 20, 30 and 40% were produced from the same isotropic mixture with essentially no variation in the particle size produced. The microemulsions made by this technique appear to be kinetically stable, remaining unchanged in particle size for years. They may be further diluted with water without any change in particle size and can be used in formulations much as with standard emulsions.