Self-emulsification mixtures

M.G. Wakerly, C.W. Pouton, B.J. Meakin, and E.S. Morton Self emulsification of vegetable oil non-ionic mixtures a proposed mechanism of action. In Phenomena in Mixed Surf actant Systems. American Chemical Society, Washington, DC (1986). 

Figure 1. Effect of Binary Mixture Surfactant Concentration and Self-Emulsification Temperature on Emulsion Droplet Size for the Miglyol 812-Tagat TO System as Determined by Laser Diffraction. Bars Represent Standard Errors.

Wakerly, M.G., Pouton, C.W., Meakin, . J., and Morton, F.S. (1986). Self-emulsification of vegetable oil-nonionic surfactant mixtures A proposed mechanism of action. A.C.S. Symposium, 311, 242-255. 

Microemulsions are transparent systems of two immiscible fluids, stabilized by an interfacial film of surfactant or a mixture of surfactants, frequently in combination with a cosurfactant. These systems could be classified as water-in-oil, bicontinuous, or oil-in-water type depending on their microstructure, which is influenced by their physicochemical properties and the extent of their ingredients. - SMEDDSs form transparent microemulsions with a droplet size of less than 50 nm. Oil is the most important excipient in SMEDDSs because it can facilitate self-emulsification and increase the fraction of lipophilic drug transported through the intestinal lymphatic system, thereby increasing absorption from the gastrointestinal tract. Long-chain and medium-chain... 

While studying phase formation when surfactants - hydrocarbon oil mixtures (i.e. three component systems) were added to increasing amounts of water (i.e. forming four component systems) it was observed that those systems which initially developed large quantities of liquid crystalline phases later formed better, finer emulsions than those systems that initially consisted of isotropic phases. These observations and their association with the process of self emulsification or easy emulsion formation in the systems investigated are presented in this report. 

The effect of AB diblock size relative to the homopolymers on the compati-bilization of A/B homopolymer blends was examined using numerical self-consistent field theory (in two dimensions) by Israels et al. (1995). They found that the interfacial tension between homopolymers can only be reduced to zero if the blocks in the diblock are longer than the corresponding homopolymer. Short diblocks were observed to form multilamellar structures in the blend, whereas a microemulsion was formed when relatively long copolymers were added to the homopolymer mixture. These observations were compared to experiments on blends of PS/PMMA and symmetric PS-PMMA diblocks reported in the same paper. AFM was used to measure the contact angle of dewetted PS droplets on PMMA, and the reduction in the interfacial tension caused by addition of PS-PMMA diblocks was thereby determined. The experiments revealed that the interfacial tension was reduced to a very small value by addition of long diblocks, due to emulsification of the homopolymer by the diblock, in agreement with the theoretical expectation (Israels et al. 1995). 

Emulsions are formed by mixing two liquids, a process which creates discrete droplets in a continuous phase. During emulsification,by mechanical agitation for example, both liquids tend to form droplets resulting in a complex mixture of 0/W and W/0 emulsions. Which of the components forms the continuous phase depends on the emulsifier used since one of the types of droplet is unstable and coalesces. Therefore, there is a need to identify the continuous phase in emulsion systems not only in the final emulsion system, but also at short times after emulsion formation or even dining the emulsification process. The NMR self-diffusion method may easily distinguish the continuous and... 

Surface-Active Materials. The active defoamer components are necessarily surface active materials, but this ancillary category covers the surfactants that are often incorporated in the formulation for other effects such as emulsification or to enhance dispersion. Emulsifiers are essential in the common oil-in-water emulsion systems, but they are also required where mixtures of active liquid components are used. For example, specialized oil-in-oil emulsifiers are needed in defoamers based on silicone/polyether mixtures, oil-in-water emulsifiers are incorporated in some defoamers even when the final product contains no water. This is to promote emulsification (self-emulsifiable) or dispersion into aqueous foaming systems. These additives increase the speed of foam decay by promoting rapid dispersion of the defoamer throughout the foaming media. Examples of emulsifying agents used in defoamer compositions are fatty acid esters and metallic soaps of fatty acids fatty alcohols and sulfonates, sulfates, and sulfosuccinates sorbi-tan esters ethoxylated products such as ethoxylated octyl or nonylphenols and silicone-polyether copolymers. 

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