Dialkyl surfactants

Whilst the occurrence of gel phases is commonly recognized for long chain dialkyl surfactants it is also a common occurrence for monoalkyl surfactants. Because of the lower packing order within the alkyl chain region in than the normal crystals, different chain length derivatives (usually up to four carbons) can mix within the Lp phase. Additionally, different head groups can also mix within the Lp phases. Indeed, Lp phases can occur for mixed systems where none is observed for the individual constituents. For example sodium dodecyl sulfate and dodecanol form a mixed gel phase where as none is observed for SDS alone [62]. (Note that dodecanol does form a stable Lp phase termed the a-crystalline phase with about 0.2 mol fraction of water [5, 63, 64].)... 

The structure of the hydrophobic tail is usually limited to either hydrocarbon or fluorocarbon chains. Compounds possessing a single such tail are the most common, although molecules with several linear or branched tails are known. Dialkyl surfactants such as lecithin (below) are particularly important naturally occurring materials. 

Additives acting on the pour point also modify the crystal size and, in addition, decrease the cohesive forces between crystals, allowing flow at lower temperatures. These additives are also copolymers containing vinyl esters, alkyl acrylates, or alkyl fumarates. In addition, formulations containing surfactants, such as the amides or fatty acid salts and long-chain dialkyl-amines, have an effect both on the cold filter plugging point and the pour point. 

In tanneries, sodium bisulfite is used to accelerate the unhairing action of lime. It is also used as a chemical reagent ia the synthesis of surfactants (qv). Addition to alpha-olefins under radical catalyzed conditions yields sodium alkylsulfonates (wetting agents). The addition of sodium bisulfite under base-catalyzed conditions to dialkyl maleates yields the sulfosucciaates. 

LialkylSulfosuccinates. Introduced in 1939 by the American Cyanamid Company under the Aerosol trademark, dialkyl sulfosuccinates have become widely used specialty surfactants (Table 8) (9). Within the limitations in hydrolytic stabiUty imposed by the presence of the ester groups, sulfosuccinates are mild, versatile surfactants used when strong wetting, detergency, rewetting, penetration, and solubilization effectiveness is needed. 

This kind of ester acts as a nonionic surfactant if the alkanol groups contain hydrophilic moieties. If only two molecules of alkanoles are added to the phosphoric acid molecule an acid or secondary dialkyl phosphoric acid ester is formed that are an amphiphilic molecule by itself see Eq. (5). 

In addition to their poor solubility in water, alkyl phosphate esters and dialkyl phosphate esters are further characterized by sensitivity to water hardness [37]. A review of the preparation, properties, and uses of surface-active anionic phosphate esters prepared by the reactions of alcohols or ethoxylates with tetra-phosphoric acid or P4O10 is given in Ref. 3. The surfactant properties of alkyl phosphates have been investigated [18,186-188]. The critical micelle concentration (CMC) of the monoalkyl ester salts is only moderate see Table 6 ... 

Non-ionic surfactants containing an amide group This group of non-ionic surfactants comprises different sub-groups, such as polyethoxylated amides, fatty acid diethanol amides, aminosu-gars and dialkyl disugar amides (gemini surfactants). 

Another important area of progress is the enlargement of the scope of the structure of aqueous aggregates. The bilayer membrane formed from dialkyl amphiphiles belongs to a new class of the aqueous aggregate, totally different from the conventional surfactant micelle. A trialkylammonium compound gives yet another type of aggregation. 

As discussed in the preceding sections, fluid, globular micelles are formed from monoalkyl surfactants, whereas the liquid-crystalline bilayer structure is formed from a variety of dialkyl amphiphiles and from single-chain amphiphiles with rigid hydrophobic segments. It may then be asked what structure is expected from amphiphiles with three alkyl chains. 

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