Surfactants functional benefits

Although the consumer products listed in Table 1 deliver a broad array of functional benefits, many of these products, by design or as a consequence of their use, make contact with the skin. Because surfactants exhibit surface activity, they interact with this living interface and produce various consequences some good, some bad, but rarely neutral. 

The ease by which the framework-forming surfactants can be removed from non-electrostatically-assembled mesostructures by low temperature solvent extraction without compromising the structural integrity of the materials is also of major benefit for the preparation of highly functionalized mesostructure derivatives. 

Synthetic surfactants are commonly used in shampoos, sometimes for reasons of cost and sometimes for performance. Non-ideal mixing in micelles can result when the repulsions between different surfactant head-groups are not uniform, such as when an anionic sulfonate is mixed with a non-ionic ethoxylate or when an anionic is mixed with a betaine. This causes the cmc of the mixture to be smaller than would be the case for ideal mixing, or for either surfactant alone. Such a reduction in cmc can be used to reduce the surfactant monomer concentration in a shampoo. This is an advantage since reducing the monomer concentration reduces the amount of eye and skin irritation experienced when the shampoo is used [904], Other synthetics offer other benefits. For example, some silicone surfactants can not only function as emulsifiers in hair and skin care products, but also act to improve feel, gloss, sheen, emolliency, conditioning and foam stabilization [905]. 

Co-solvents in metered dose inhalers were commonly used in CFG formulations to aid in drug solubilization. In HFA formulations, co-solvents continue this same function, but have additional benefits in the new systems, such as solubilization of other excipients. Vervaet and Byron discuss water solubility in the various propellants addressed here, where the addition of ethanol to the HFA system considerably increases the solubility of water (Vervaet and Byron, 1999). Likewise, ethanol was found to increase the solubility of several surfactants in HFA (Vervaet and Byron, 1999 Stein and Stefely, 2003). Suspension formulations using this technique (surfactant plus ethanol) must be made with caution however, as ethanol can also increase the solubility of the drug substance, potentially causing increased particle growth via Ostwald ripening. Nonetheless,... 

Another important class of nonionics are amine oxides, such as DMDAO (dimethyldodecyl amine oxide) and CAPAO (cocoamidopropyldimethyl amine oxide). This type of surfactant is nonionic at pH values above its pKa and cationic below that point. When functioning as a nonionic, amine oxides have many useful properties. They interact strongly with anionics which can result in performance benefits [17]. Amine oxides help to mitigate anionic surfactant irritation, act as foam stabilizers, and can also function to improve grease removal. 

The main function of the primary surfactants in a shampoo is to provide a cleaning benefit. Primary surfactants are also necessary for adequate foam and viscosity control. As stated above, levels of surfactant between 8 and 20% are generally employed in shampoos. These levels are chosen primarily to provide acceptable lather and viscosity, since many common soils, e.g., sebum, are adequately cleaned at lower surfactant concentrations. 

Polymerization offers an approach to making vesicle formulations suitable for appUcations. The maj or benefits of polymerization include increasing the chemical-mechanical strength of the vesicle architecture, and the potential for performing subsequently a variety of reactions to create a highly functionalized surface. The most common approach to polymerization in vesicles is to use polymerizable surfactants (Fig. 2a). The use of polymerizable surfactants is best described as the polymerization of vesicles or fixation of vesicles, and so is a synergistic template synthesis. Typically, unsaturated biological surfactants have been specificaUy synthesized for these types of polymerizations, and there are a number of excellent reviews of this subject [3-6]. 

Amine oxides, in their nonionic forms (depending on the pH), are best known for their functionality as secondary surfactants, since they enhance foam characteristics and provide thick, creamy, and more stable lather at moderate acidic pHs. They are also mild to skin and hair, and since the N-0 bond is highly polarized and exists in a protonated form at low pHs, they may provide some conditioning and antistatic benefits. 

The majority of silicone polymers/surfactants that are used in today s personal care industry are of the nonionic types. Since the derivatives of polysiloxanes could be ionic completely or partially, the properties exhibited by such compounds are different and therefore provide an entirely new range of properties and benefits. For example, cationic and amphoteric functional groups, because of increased substantivity on the hair surfaces and durable surface covering, provide antistatic effects. Polymethoxylsiloxanes modified with cationic and amphoteric groups provide both antistatic benefit as well as high gliding ability, which are very useful in personal care applications. ... 

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