Surfactants used in cosmetic formulations

This section, which is by no means exhaustive, will deal with the following topics (i) Surfactants used in cosmetic formulations, (il) Interaction forces between particles or droplets in a dispersion and their combination, (iil) Description of stability in terms of the interaction forces, (iv) Self-assembly structures and their role in stabilization, skin feel, moisturization and delivery of actives, (v) Use of polymeric surfactants for stabilization of nanoemulsions, multiple emulsions, liposomes and vesicles. 

As mentioned above, surfactants used in cosmetic formulations must be completely free of allergens, sensitizers and irritants. To minimize medical risks, cosmetic formu-lators tend to use polymeric surfactants which are less likely to penetrate beyond the stratum corneum and hence they are less likely to cause any damage. 

Conventional surfactants of the anionic, cationic, amphoteric and nonionic types are used in cosmetic systems. Besides the synthetic surfactants that are used in preparation of cosmetic systems such as emulsions, creams, suspensions, etc., several other naturally occurring materials have been introduced and there is a trend in recent years to use such natural products more widely, in the belief that they are safer for application. As mentioned above, polymeric surfactants of the A-B, A-B-A and BAn types are also used in many cosmetic formulations. 

Several synthetic surfactants that are applied in cosmetics may be listed such as carboxylates, ether sulfates, sulfate, sulfonates, quaternary amines, betaines, sarcosi- 

The macromolecular surfactants possess considerable advantages for use in cosmetic ingredients. The most commonly used materials are the ABA block copolymers, with A being poly(ethylene oxide) and B polyfpropylene oxide) (Pluronics). On the whole, polymeric surfactants have much lower toxicity, sensitization and irritation potentials, provided they are not contaminated with traces of the parent monomers. As will be discussed in the section on emulsions, these molecules provide greater stability and in some cases they can be used to adjust the viscosity of the cosmetic formulation. 

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Biosurfactants are microbial surface active compounds and have tremendous applications in cosmetics due to their high surface activity and multifarious bioactivities. Surfactants are widely used in cosmetics for stabilizing the oH—water emulsion and uniformly dispersing various components. The key feature of surfactants used in cosmetic formulation is their skin friendly nature, which means that the surfactant is safe and compatible with the skin. The advantages of biosurfactants over chemical surfactants are their... 

The reaction product with monoethanolamine acts as a thickening agent [41,101] and with alcohols as an emollient [40]. Also reaction products with amino acids and oligo- or polypeptides for use in cosmetic formulations are known [43]. Sorbitan esters from ether carboxylates are described as emulsifiers or mild surfactants in cosmetic formulations [39] and alkyl ether carboxylic acid taurides as nonirritant anionic surfactants for cosmetic cleaners in particular [44]. Using unsaturated ether carboxylates it is possible to make viscous formulations based on combinations of unsaturated and saturated ether carboxylates [111]. Highly purified alkyl ether carboxylates based on alcohol ethoxylates with low free alcohol content have also been described [112]. 

Economical high foaming surfactants used in the formulation of mild shampoos, cosmetics, and household cleaners. Also used in the emulsion polymerization of PVC and styrene/ butadiene resins. 

Several natural surfactants are used in cosmetic formulations, such as those produced from lanolin (wool fat), phytosteroids extracted from various plants and surfactants extracted from beeswax. Unfortunately, these naturally occurring surfactants are not widely used in cosmetics due to their relatively poor physicochemical performance when compared with the synthetic molecules. 

Use of MS provides structural information about the surfactants employed in cosmetic formulations. Owing to the low volatility of surfactants, ionization techniques such as fast... 

Uses Surfactant intermediate quaternized end prods, used in cosmetic formulations... 

Betaines are insensitive to water hardness, almost nontoxic, mild to the skin and have antimicrobial properties. They are therefore used in cosmetic formulations and in household cleaners. They are compatible with other surfactants and have good washing and foaming performance. 

Besides the alkyl ether carboxylates the amidether carboxylates are used as mild surfactants in cosmetic formulations [35-37,68,69,71,80]. As described by Meijer [68,69], the ether carboxylate mixture derived from the monoethanol-amide of coconut oil is a mild product in shampoos and showerbaths, and the stearylmonoethanolamidether carboxylate an oil-in-water emulsifier for creams and lotions. The NDELA content of these products is below the detection level of 10 ppb because of the use of monoethanolamine and the further chemical reactions after amidation. 

Industrially, silicone surfactants are used in a variety of processes including foam, textile, concrete and thermoplastic production, and applications include use as foam stabilisers, defoamers, emulsifiers, dispersants, wetters, adhesives, lubricants and release agents [1]. The ability of silicone surfactants to also function in organic media creates a unique niche for their use, such as in polyurethane foam manufacture and as additives to paints and oil-based formulations, whilst the ability to lower surface tension in aqueous solutions provides useful superwetting properties. The low biological risk associated with these compounds has also led to their use in cosmetics and personal care products [2]. 

Emulsions of fatty- and petroleum-based substances, both oils and waxes, of the o/w type are made by using blends of sorbitan fatty esters and their poly(oxyethylene) derivatives. Mixtures of poly(oxyethylene(20)) sorbitan monostearate (Polysorbate 60) and sorbitan monostearate are typical examples of blends used for lotions and creams. Both sorbitan fatty acid esters and their poly(oxyethylene) derivatives are particularly advantageous in cosmetic uses because of their very low skin irritant properties. Sorbitan fatty ester emulsifiers for w/o emulsions of mineral oil are used in hair preparations of both the lotion and cream type. Poly(oxyethylene(20)) sorbitan monolaurate is useful in shampoo formulations (see Hairpreparations). Poly(oxyethylene) sorbitan surfactants are also used for solubilization of essential oils in the preparation of colognes and after-shave lotions. 

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. ... 

Cetrimide is a quaternary ammonium compound that is used in cosmetics and pharmaceutical formulations as an antimicrobial preservative see Section 10. It may also be used as a cationic surfactant. In eye-drops, it is used as a preservative at a concentration of 0.005 % w/v. 

Cetylpyridinium chloride is a quaternary ammonium cationic surfactant, used in pharmaceutical and cosmetic formulations as an antimicrobial preservative see Section 10. It is used therapeutically as an antiseptic agent used alone or in combination with other drugs for oral and throat care used in nonparenteral formulations licensed in the UK and used in oral and inhalation preparations at concentrations of 0.02-1.5 mg (see Section 16). 

Sorbitan esters are widely used in cosmetics, food products, and pharmaceutical formulations as lipophilic nonionic surfactants. They are mainly used in pharmaceutical formulations as emulsifying agents in the preparation of creams, emulsions, and ointments for topical application. When used alone, sorbitan esters produce stable water-in-oil emulsions and microemulsions but are frequently used in combination with varying... 

Within the last 30 years, micro emulsions have also become increasingly significant in industry. Besides their application in the enhanced oil recovery (see Section 10.2 in Chapter 10), they are used in cosmetics and pharmaceuticals (see Chapter 8), washing processes (see Section 10.3 in Chapter 10), chemical reactions (nano-particle synthesis (see Chapter 6)), polymerisations (see Chapter 7) and catalytic reactions (see Chapter 5). In practical applications, micro emulsions are usually multicomponent mixtures for which formulation rules had to be found (see Chapter 3). Salt solutions and other polar solvents or monomers can be used as hydrophilic component. The hydrophobic component, usually referred to as oil, may be an alkane, a triglyceride, a supercritical fluid, a monomer or a mixture thereof. Industrially used amphiphiles include soaps as well as medium-chained alcohols and amphiphilic polymers, respectively, which serve as co-surfactant. 

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