Other Types of Surfactants

Phosphorus-containing surfactants often possess particular properties by themselves or in combination with other types of surfactants. They are therefore proposed for fields of application which can only be covered by other surfactants with difficulty. Their wide variety enables them to become tailored for different requirements. Further possibilities can be developed in conjunction with other surfactants. Their solubility in saline solution extends their field of application beyond the limits for common surfactants. 

At the end of the 1990s statistics show that the non-ionic surfactants achieved the highest growth in production rates world-wide, though anionic surfactants (anionics) maintained the dominant position in the surfactant market. Today they are produced in a larger variety by the petrochemical industry than all other types of surfactants. Their production spectrum covers alkyl sulfates (ASs), secondary alkane sulfonates (SASs) and aryl sulfonates and carboxylates via derivatives of partly fluorinated or perfluorinated alkyl surfactants to compounds with an alkylpolyglycolether substructure combined with an anionic moiety such as alkylether sulfates (AESs), phosphates, phosphonates or carboxylates. 

Although these surfactants represent less than 1% of the U.S. production of surfactants, the market use is increasing dramatically because of their unique properties [353]. Of particular importance is the synergistic effect that amphoteric surfactants have when used in conjunction with other types of surfactants. The non-eye-stinging characteristic of these compounds has been responsible for the upsurge in the baby shampoo market over time [354,355]. 

The use of zwitterionic surfactants commercially has increased dramatically in recent years (U because of their unique properties, such as compatibility and synergism when used in conjunction with most other types of surfactants. This type of surfactant is used in textile processing aids, cosmetic products, cleaning agents, and as antistatic agents. The sulfobetaines have been found to be very good lime soap disperants ( ). 

Their ability to render compatible various surfactants and other types of surfactants into strong solutions of electrolyte make them invaluable in the formulation of strong detergent products where mildness is not an issue. 

It is clear that the approach of utilizing other types of surfactant aggregate mor-... 

Our own involvement in microemulsion research was very much influenced by the contacts with the Swedish masters in the field of phase behaviour, Ekwall and Friberg, and at a later stage Shinoda, as well as by our previous experience of studying molecular interactions and association phenomena for other types of surfactant systems. Regarding the stability issue, we found it useful to suggest a definition [32] of a microemulsion as a system of water, oil and amphiphile which is a single isotropic and thermodynamically stable liquid solution . While this definition certainly provided nothing new, we felt it contributed to eliminate some confusion. 

Not surprisingly other cationic surfactants and the alternative surfactant systems listed in Table 1 were also able to generate the three basic structures. The cubic MCM-48 type was most difficult to synthesize and consequently quite rare. Other types of surfactants and/or alternative media (acidic or neutral) allowed preparation and recognition of additional structural kinds of mesoporous materials (which could also be correlated with certain g values). More than 20 types of silica mesoporous materials are listed in a recent compilation as unique in terms of structure and/or method of assembly [18]. Several new cubic structures... 

We usually associate antiirritation with amphoteric surfactants however, because other types of surfactants, such as glucamide or alkyl poly glucoside (APG), perform this function and these are structurally not amphoterics or cationics, I suggest that we call this type of surfactant a pseudo-amphoteric surfactant. Furthermore, I would propose that we promote the concept of classifying surfactants on the basis of their function rather than their structure. More on this subject will be presented in the following sections. 

Although we have not tested this effect for other types of surfactants, it is clear that molecular weight (size) does explain a large part of skin swelling. Because skin swelling correlates with skin irritation by surfactants, molecular weight must explain a large part of skin irritation. This is because... 

When a relatively small amount of surfactant is added to water, part of it is dissolved the dissolved molecules move freely in the aqueous phase. The other part is reversibly adsorbed on the interfaces present. The free and adsorbed surfactant molecules are subject to an adsorption/desorption equilibrium. The greater their affinity to the substrate, the stronger their adsorption. The well-known Langmuir equation is often used to quantitatively describe the adsorption of surfactants, particularly in the case of anionic surfactants. For other types of surfactants or mixtures of them, other equations may apply for details in this regard, the reader is referred to specialized textbooks [25, 26] and articles [27-29]. 

The majority of miniemulsions reported in the literature have been stabilized with anionic surfactants such as sodium dodecyl sulfate (SDS), probably because of the widespread use of anionic surfactants in conventional emulsion polymerization, and due to their compatibility with neutral or anionic monomers and anionic initiators. Other types of surfactant have also been used, such as cationic, nonionic, and mixed nonionic/anionic, reactive as well as nonreactive surfactants. The surfactants useful for miniemulsion polymerization should meet the same requirements as in the conventional emulsion polymerization. 

Abandoning the dispersion concept of microemulsions and realizing that they are closely related to micelles, liquid crystals, and other types of surfactant self-assemblies but distinctly different from (macro) emulsions clearly makes the term microemulsion less suitable. However, it has been kept for historical reasons. Confusion because of the wording continues, not so much concerning the thermodynamics but as regards microstructure it seems that the term easily directs the mind toward a structure of discrete objects, droplets, while we now know that this is not the typical situation. 

The different demands of a surface-active system can be met either by blending these main types with each other or with other types of surfactants. This is, in most cases, the best way to optimize costs, performance and environmental impact. 

The viscosity of aqueous solutions of ether sulfates can be increased by adding an electrolyte, usually common salt. This effect depends on salt concentration and the structure of the particular ether sulfate. As a general rule, it can be said that this thickening effect will happen at lower concentrations of salt, the more branched parts there are in the alkyl chain. This means, in practice, that thickening of solutions of alkyl ether sulfates based on oxoalcohols with a proportion of branched alkyl chains will occur at lower concentration of salt than is the case for alkyl ether sulfates based on pure linear alcohols. The increase of viscosity by the addition of salt also takes place in mixtures of ether sulfates with other types of surfactants. 

Phosphorus-containing surfactants exhibit a good solubility in saline solutions, they are insensitive to water hardness, they are able to disperse lime soap, and they act as corrosion inhibitors in acid media. They are also valuable components for obtaining synergistic effects due to the variety of possible molecule structures. However, until now this opportunity has only been seldom used, as can be deduced from the literature. In some fields of application, phosphorus-containing surfactants obviously offer many benefits when compared to other types of surfactants. In such cases, they have been applied to great advantage. 

The practical potential of nonionic MLC was demonstrated by the use of micellar solutions of Brij 35 in the analysis of tobacco [18], Samples of smoking tobacco were extracted with an ueous solution of 30% Brij 35, and an aliquot of the extract was chromatographically separated without further preparation, with a 6% Brij 35 mobile phase. Comparison with an aromatic aldehyde standard mixture enabled verification of vanillin and ethylvanillin as two of the extract components. Brij 35 was chosen for this study over other nonionic surfactants (such as Tritons , Spans , Igepals or Tweens ) on the basis of its commercial availability, high purity, low cost, low toxicity, high cloud temperature, and low background absorbance, compared to the other types of surfactants mentioned. Brij 35 does not possess a strong chromophore and its absorption is minimal. 

These surfactants are well established as extremely mild surfactants [7]. They are referenced in the CTFA dictionary as sodium coco (or lauryl) amphoacetate and disodium coco (or lauryl) amphodi-acetate. Amphoterics are widely used in mild, tear-free shampoos and sensitive skin cleansers due to their favorable surfactant properties, low irritation profile, and irritation-mollifying properties [8], Amphoacetates or diacetates are excellent foaming agents, even in hard water, and they exhibit compatibility with all other types of surfactants. 

Subsequently, additional conunercial processes were developed for synthesis of a range of per- and poly-fluorinated surfactants whose unique properties make them largely irreplaceable in many applications. The widespread use and disposal and the high stability of the perfluoroalkyl acids, which do not breakdown readily either abiotically or biotically in the environment, has resulted in widespread presence of PFAAs in the environment. This caused commercial production to shift toward short chain alternatives and new fluorinated moieties such as the per- and poly-fluorinated ethers. Clearly, there remains a need for fluorinated surfactants in many industries to obtain the beneficial performance properties of these substances that cannot be achieved with other types of surfactants. 

Thomas RR (2006) Other types of surfactants - fluorinated surfactants. (In Chemistry and Technology of Surfactants). Blackwell, Oxford, UK, pp 227-235... 

Nonionic surfactants have been added to various acid formulations [54, 56, 84], These surfactants are chosen because they maintain low interfacial tension between the acid and oil. They are inexpensive, and can be mixed with other types of surfactants to enhance their properties [85]. However, in common with other types of surfactants, they should be carefully tested before field applications. Nonionic surfactants can separate out of solution under certain conditions, as will be explained in the next section. 

It is to be expected that other types of surfactant-sensitive electrodes can be used with equal or greater success, and it would not be surprising if the two-phase methods, e.g. that of Cross (section 7.1.3) could also be used, although the author is unaware of any published evidence. 

This classification is very useful especially for other types of surfactant-inorganic interactions such as those involving neutral surfactants as structure directors (templates). Such interactions can be denoted as follows ... 

These have the advantage over ionic surfactants in their compatibility with most other types of surfactants, they are little affected by moderate pH changes and moderate electrolyte concentrations. A useful scale for describing nonionic surfactants is the hydrophUic-lipophilic balance (HLB), which simply gives the relative proportion of hydrophilic to lipophilic components. For a simple nonionic surfactant such as an alcohol ethoxylate, the HLB is simply given by the percentage of hydrophilic components (PEO) divided by 5. 

---