Hydrocarbons surfactants

Liquid Third Phase. A third Hquid with coUoidal stmcture has been a known component in emulsions since the 1970s (22) for nonionic surfactants of the poly(ethylene glycol) alkylaryl ether type. It allows low energy emulsification (23) using the strong temperature dependence of the coUoidal association stmctures in the water—surfactant—hydrocarbon systems. 

It has been proposed that the overlapping of the surfactant hydrocarbon tails is mainly responsible for the micelle-micelle interactions [247]. However, since tail-tail interactions are of the same order of magnitude as tail-apolar solvent interactions, it seems more reasonable to consider the overlapping of the surfactant hydrocarbon tails as an effect rather than the origin of the micelle-micelle interactions. 

Raney K, Benton W, Miller CA (1987) Optimum detergency conditions with nonionic sm-factants I. Ternary water-surfactant-hydrocarbon system. J Colloid Interface Sci 117 282-290... 

Micelles are spontaneously formed by most surfactants (especially single-chained ones) even at fairly low concentrations in water, whereas at higher surfactant concentrations, with or without the addition of an oil (e.g. octane) or co-surfactant (e.g. pentanol), a diverse range of structures can be formed. These various structures include micelles, multibilayers (liquid crystals), inverted micelles, emulsions (swollen micelles) and a range of microemulsions. In each case, the self-assembled structures are determined by the relative amounts of surfactant, hydrocarbon oil, co-surfactant (e.g. pentanol) and water, and the fundamental requirement that there be no molecular contact between hydrocarbon and water. 

Let us consider now the case of a specific ionic polysaccharide. The unique properties of complexes of the cationic chitosan with non-ionic sorbitan esters provides an interesting example. Grant and co-workers (2006) have established that mixtures of chitosan and surfactant form emulsion-like solutions and/or creams, where the surfactant component is present as droplets or micelle-like particles and the chitosan solution acts as the system s continuous phase. It was established that the length and the degree of saturation of the surfactant hydrocarbon chain have a significant impact on the development of the chitosan-surfactant complexes. Moreover, an optimal distance between the chitosan s protonated amine groups is required for effective interactions to occur between the polysaccharide and the sorbitan esters. 

In surfactant solutions, these molecules tend to remain in the hydrophobic domains. Interaction between the dyes and the polar head groups of the surfactants prevents aggregation of these dyes in the a-ZrP galleries. Surfactant-dye and matrix-dye interactions align the chromophores with the charge centers closer to the a-ZrP surface, and the hydrophobic ends are buried in the surfactant hydrocarbon chains. The binding of the dyes to the surfactant-a-ZrP matrix is confirmed from powder x-ray diffraction studies as well as from centrifugation studies [69],... 

Solid soils are commonly encountered in hard surface cleaning and continue to become more important in home laundry conditions as wash temperatures decrease. The detergency process is complicated in the case of solid oily soils by the nature of the interfacial interactions of the surfactant solution and the solid soil. An initial soil softening or "liquefaction", due to penetration of surfactant and water molecules was proposed, based on gravimetric data (4). In our initial reports of the application of FT-IR to the study of solid soil detergency, we also found evidence of rapid surfactant penetration, which was correlated with successful detergency (5). In this chapter, we examine the detergency performance of several nonionic surfactants as a function of temperature and type of hydrocarbon "model soil". Performance characteristics are related to the interfacial phase behavior of the ternary surfactant -hydrocarbon - water system. 

Calcium sulphate in phosphoric acid (wet process for phosphoric acid) Petroleum sulphonate surfactants/hydrocarbon liquid Conditioned in mixer, pellets formed by tumbling... 

FIG. 2.12 Addition of a hydrotrope (that of Figure 2.9) to a lamellar hquid crystal gives a reduction of the order parameter of the surfactant hydrocarbon chain (o) addition of a surfactant gives no change in order ( ). 

Information is obtained by modeling the competition between surfactant ions and other ions for adsorption sites on the floe surface. A statistical mechanical approach, as previously employed for couperative surface phasomena (e.g., hemimicelle formation), allows one to observe diet excessive concentrations of surfactant interfere with the flotation of paniculate material. This apparently results from the formation of a second bemimicelle of condensed surfactant on lop of the first, with the surfactant polar or ionic heads presented to the water this results in a hydrophilic surface (Fig. 17.2-4). The effects or ionic strength and surfactant hydrocarbon chain length on this behavior heve been modeled malhemeticaliy. 

Traube rule, more often referred to as the Traube rule. In agreement with eq. (II. 12), the Ducleaux-Traube rule corresponds to a linear relationship between the surfactant chain length and the p0 - pj,s) value. The latter may be viewed as the work of adsorption performed under standard conditions. Indeed, let us assume that the work of adsorption, p0 - p(0s), is a linear function of the number of carbon atoms in the surfactant hydrocarbon chain, i.e ... 

The quantity Acc relative, or dimensionless, concentration corresponding to two-dimensional vapor saturation increases with increasing temperature and decreasing surfactant hydrocarbon chain length. If the formation of liquid expanded adsorption layers takes place, the T(c) dependence is smoother (curve 2 in Fig. II-26). 

Petroleum reservoirs can exhibit the full range of wettabilities from water-wet to oil-wet (53). Adsorption of crude oil heavy ends modifies solid surface properties and is thought to change reservoir wettability toward more oil-wet. Surfactant adsorption on hydrophobic surfaces takes place by hydrophobic interactions between surfactant hydrocarbon chains and the solid surface (35, 54—58). At low surfactant concentrations, surfactant molecules are oriented parallel to the surface. As the surfactant concentration increases, hydrophobic interactions between surfactant hydrophobes become significant. The surfactant molecules become oriented vertically to the surface with the polar groups toward the aqueous phase. 

Nuclear magnetic resonance relaxation is a useful experimental technique to study surfactant aggregation in liquid solutions and liquid crystals [2,50,51]. It yields information on the local dynamics and the conformational state of the surfactant hydrocarbon chain and has, for example, demonstrated the liquidlike interior of surfactant micelles. However, the aim of NMR relaxation studies of microemulsions is often to study properties such as the surfactant aggregate (droplet) size. 

Figure 22 A schematic illustration of the various coordinate frames considered within the two-step model, for the case of a specifically deuterium-labeled methylene segment in the surfactant hydrocarbon chain. The laboratory frame (L) is set by the direction of the external magnetic field, where Zjl is the field direction. In this frame the nuclear quadrupolar moment tensor is diagonal. The director frame ( >) is associated with the micellar aggregate where Z/> specifies the micellar surface normal. It is assumed that the fast local dynamics occur with an essentially cylindrical symmetry around Z/). The molecular frame (Af) corresponds to the principal axis of the electric field gradient tensor. For the case of a methylene segment, Zm specifies the direction maximum component of the field gradient tensor, which is furthermore cylindrically symmetrical around Zm-...

Very large micelles may also form in binary surfactant systems. These are long wormlike micelles that become entangled at higher concentrations, giving rise to rheological properties similar to those in polymer solutions. Such systems have been examined by H band shape analysis [52,53]. The protons of the surfactant hydrocarbon chain form a very large dipolar coupled spin system with an essentially continuous distribution of transverse relaxation rates. The distribution of relaxation rates is related to the distribution of order... 

Water-free microemulsions can be designed with glycerol as the polar component. The solubility of glycerol in surfactant-hydrocarbon systems is normally smaller than in water, however. With AOT as surfactant and heptane as oil component, about 5 mol of glycerol can be solubilized per mole of surfactant at 0°C, this amount decreasing with increasing temperature [100]. 

In the above equation ftjjj, and ftpg are the thickness of the region oeeupied by the surfactant hydrocarbon chain and... 

Kunieda, H. (1989) Phase behaviors in water/nonionic surfactant/hydrocarbon and water/nonionic surfactant/ amphiphilic oil system. J. Colloid Interface Sci., 133, 237-243. 

---