Compounds with two or more groups that are insoluble in each other are called amphiphilic materials. The presence of these groups makes the surface of the molecule active.
Surface-active materials are important because they alter surface tension, a necessary first step in providing wetting, spreading, emulsification, detergency and cosmetic beauty. The use of surfactants in aqueous formulations is the most well-known example of surfactant use. A less popular use of surfactants is to modify oils to reduce surface tension, thereby improving spreadability, wetting and gelling. The use of correctly selected amphiphilic silicone molecules can allow one to replace traditional silicone compounds (including D5 and fluids) with natural oils, esters and other products with green profiles. This process is called “silicone greening.”
The physical chemistry of most cosmetic formulations is so complex that a detailed analysis of what happens to the surface during product application is sufficient to a chemically advanced level. The reason for this is that the preparation is a complex combination of ingredients including water, oil, surfactants, antimicrobials, salts and many other ingredients. All formulas contain surface tension regulators, which are essential prerequisites for wetting, emulsification, foaming and detergency. The interaction of all the various components is a controlling property of the formulation and not the properties of the various components alone or neatly in the solvent. We have addressed the interactions between (a) anionic and cationic surfactant 1, (b) anionic and amphoteric surfactant 2, and (c) anionic and cationic gemini surfactants; all of these are aqueous systems. This article will explore oil-based systems and the synergistic interactions between alkylsiloxanes and oils.
