Surfactant formulations microstructure

With all these factors in mind, we have attempted to carry out the emulsions aspect of the investigations at the University of Florida Improved Oil Recovery Research Program (4,5). The emulsion systems contain TRS 10-410, isobutanol, sodium chloride, dodecane and water. Extensive physical property data and micro-structural studies of the aqueous surfactant formulations have been already reported by Vijayan et al. (6). Also, the structural aspects of the emulsions containing the same species with aqueous to oil ratio of 1 1 as well as various physical property data as a function of salt concentration have been reported by Vijayan et al. (7). A detailed study of the middle phases formed by the same surfactant formulation with dodecane oil with respect to microstructural changes and microemulsion (swollen micelle) phase inversion has been reported by Ramachandran et al. (8). 

Relatively, efficient microemulsion formulations, typically those with less than 20 wt% surfactant, differ significantly from non-ideal solutions in that they contain a distinct type of microstructure, i.e. topologically ordered oil and water domains coated by surfactant. The microstructures within microemulsions typically range from 3 to 100 nm in size, and fluctuate rapidly in time. As the oil-to-water ratio in microemulsion phases is increased, many experimental studies indicate that a continuous progression of microstructures is observed. At low concentrations of oil, droplets of oil, coated with surfactant, swim in a continuous water domain (an oil-in-water microemulsion). As the concentration of oil is increased, the spherical droplets form oblong and globular structures. At intermediate ratios of oil to water (near 50/50), a so-called bicontinuous structure of oil and water domains is observed (12). As a... 

Two main microemulsion microstructures have been identified droplet and biconti-nuous microemulsions (54-58). In the droplet type, the microemulsion phase consists of solubilized micelles reverse micelles for w/o systems and normal micelles for the o/w counterparts. In w/o microemulsions, spherical water drops are coated by a monomolecular film of surfactant, while in w/o microemulsions, the dispersed phase is oil. In contrast, bicontinuous microemulsions occur as a continuous network of aqueous domains enmeshed in a continuous network of oil, with the surfactant molecules occupying the oil/water boundaries. Microemulsion-based materials synthesis relies on the availability of surfactant/oil/aqueous phase formulations that give stable microemulsions (54-58). As can be seen from Table 2.2.1, a variety of surfactants have been used, as further detailed in Table 2.2.2 (16). Also, various oils have been utilized, including straight-chain alkanes (e.g., n-decane, /(-hexane),... 

Usually the surfactant concentration in ointments and creams is significantly lower than in surfactant gels. Ointments are non-aqueous preparations, whereas creams result from ointments by adding water. The microstructure of both ointments and creams may consist of liquid crystals, as long as a liquid crystalline network or matrix is formed by amphiphilic molecules. In a liquid crystalline matrix, it is easier to deform the system by shear such formulations show plastic and thixotropic flow behavior on shear. In comparison to systems with a crystalline matrix which are usually destroyed irreversibly by shear, those with a liquid crystalline matrix exhibit a short regeneration time of... 

Cetostearyl alcohol is used in cosmetics and topical pharmaceutical preparations. In topical pharmaceutical formulations, cetostearyl alcohol will increase the viscosity and impart body in both water-in-oil and oil-in-water emulsions. Cetostearyl alcohol will stablize an emulsion and also act as a co-emulsifier, thus decreasing the amount of surfactant required to form a stable emulsion. Cetostearyl alcohol is also used in the preparation of nonaqueous creams and sticks. Research articles have been published in which cetostearyl alcohol has been used to slow the dissolution of water-soluble drugs.In combination with surfactants, cetostearyl alcohol forms emulsions with very complex microstructures. These microstructures can include liquid crystals, lamellar structures, and gel phases. ... 

For phenohc foam production surfactants and blowing agents are added to aqueous resoles. The surfactant, also called the cell regulator, lowers the surfece tension of the resin formulation and provides an interfece between the non-polar blowing agent and the polar resin phase. Surfactants influence foam microstructure. 

A major application of oxide nanoparticles is fabrication of ceramics (including substrates) with dense microstructure. Synthesizing such particles from macroemulsions (as compared to microemulsions) adds the advantage of using only small quantities of surfactants in the formulations and keeping the system low in pollutants. Examples of such endeavors are discussed below. 

Surfactant is another key component in controlling the emulsion polymerization process, which plays an important role in formulating polymers that preserve microstructures of tunable topology and the length scale of the parent microemulsion template. [21]... 

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