Hydrogen surfactants

FIG. 22 Side view snapshots of a simulation of a 16-carbon hydrogenated surfactant chain with a carboxylate-like head group on a water surface at 300 K. The view iu (a) (top) is au area of 0.21 um molecule (b) (bottom) is at 0.21 um molecule . These two areas roughly bracket a first-order trausitiou with some features of the LE-LC transition. See also Figure 23 for the correspoudiug pressure-area isotherm. (Reproduced with permission from Ref. 364. Copyright 1992 American Chemical Society.)... 

Fig. 2 shows a schematic of a set of contrast variation SANS experiments that could be performed to determine the detailed molecular architecture of a micelle, assuming that the various deuterated forms are available. Fig. 2A shows micelles formed from fully hydrogenous surfactant dispersed in D2O In this case, the information obtained from the SANS experiment is primarily about the whole micelle, i.e., its shape and size. Fig. 2B shows the micelles formed by the chain-deuterated version of the surfactant in D2O In this experiment, information is mainly obtained about the head group region (shell) of the micelle. Finally Fig. 2C shows the micelles formed from the chain-deuterated version of the surfactant in H2O In this case, information is obtained about the chain region of the surfactant. It is possible to simultaneously fit the SANS data obtained for these three systems to obtain a self-consistent, detailed picture of the size. 

The aggregation of fluorinated surfactants in nonaqueous solvents has also been studied. These surfactants form aggregates at lower concentrations than ordinary hydrogenated surfactants in water. Chrisment et al. have studied nonionic fluoro-alkyllipopeptides in DMSO and found progressive and very limited aggregation in this solvent as expected from the low polarity of the solvent [65], In addition, the lithium salt of nonadecafluorodecanoic acid has been studied with 19F NMR in formamide, A-methylformamide, and ethylene glycol [66],... 

These two kinds of surfactants are mutually insoluble in aqueous systems, and they can form separated hydrogenated surfactant micelles that coexist with fluorinated surfactant micelles. Consequently, mesoporous silica with a bimodal pore-size distribution can be obtained, because of the coexistence of these two different types of aggregates that template two different pore sizes. An example of bimodal mesoporous silica is shown in Figure 11.13. 

Sodium laureth-6 carboxylate Sodium laureth-13 carboxylate surfactant. It. duty cleaners Ammonium nonoxynoM sulfate surfactant. It. duty detergents Disodium PEG-4 cocamido MIPA sulfosuccinate Dodecylbenzenesulfonic acid surfactant, It.-colored epoxy curing agents Dimer acid, hydrogenated surfactant, lubricant ester derivs. 

Dimer acid, hydrogenated surfactant, lubricants Diisotridecyl adipate Glyceryl isostearate Glycol stearate lsolaureth-3 lsolaureth-6 lsolaureth-10 Isooctyl oleate Isooctyl stearate Isotridecyl stearate Laureth-4 PEG-4 castor oil PEG-52 castor oil PEG-7 glyceryl cocoate PEG-10 tallate PEG-200 trihydroxystearin... 

TIPA-lauryl sulfate Jrideceth-2 phosphate Trideceth-5 phosphate Tridecyl stearate Trimethylolpropane tripelargonate surfactant, thermographic resins Dimer acid, hydrogenated surfactant, thickeners... 

Whatever the specific type, a valid question for all ordinary emulsions with or without surfactants is what is the maximum amount of the dispersed phase in the continuous phase when the former will still remain dispersed In other words, at what volume ratio does an inversion (i.e. OAV to W/O and the reverse) take place Emulsions for particle preparation are known to have been prepared where the volume ratio of the two phases can go up to near 1 1 [18]. In addition and contrast to this general idea about the relative contents of the two phases, one must also refer to the highly concentrated water-in-oil emulsions which can be prepared with a fluorinated surfactant and a fluorocarbon/hydrogenated surfactant (pronouncedly hydrophobic) and a hydrocarbon [19]. In these W/O emulsions, up to 98% w/w water is added, but inversion is never achieved. Highly concentrated W/O emulsions have also been described recently by Hakansson etal. [20] where the surfactant is of the alcohol ethoxylated type, the dispersed phase is aqueous in nature and the continuous phase, an aliphatic hydrocarbon. It has been indicated that such emulsions may contain more than 99% of the dispersed phase. These are, however, very special cases and do not demand further discussion here. Without going into specificities, let us look at the general factors that may influence inversion [3, 21, 22] ... 

Mixtures of hydrocarbon (CH) and fluorocarbon (CF) surfactants can provide important considerations for both theoretical and applied interest. Their properties have been reviewed. Similar to hydrogenated surfactant mixtures, the ones of hydrocarbon and fluorocarbon surfactants can also self-assemble into various aggregates, including mixed micelles and vesicles. However, completely different phase behavior and self-assembly of CH/CF surfactant mixtures can be observed because of the repellence between the two hydrophobic chains. Several advantaged techniques, including SANS, SAXS, F- and H-NMR, cryo-TEM, and Freeze-fracture TEM (FF-TEM) have been widely employed to characterize these systems. ... 

The behaviour of a real microemulsion is much more complex than the idealised system described above and the SANS studies are capable of revealing much more detailed information on the structure. A few illustrative examples are provided below. Since the microemulsion consists of three different regions the use of H/D isotope substitution (see Table 2 in previous chapter) can be used to vary the p-value of each region independently. In practice, it is much easier to use D2O in the central core and hydrogenated surfactant and oil components as shown in Figure 7a but some experiments have also been done with the inverted system shown In Figure 7b or for various H/D combinations (Figure 7c). 

W/0 gel emulsions, stabilised by hydrogenated surfactants with hydrocarbon oils, and fluorinated surfactants with fluorocarbon oils, and on OAV gel emulsions have been conducted. It is convenient to summarise their pre-paration, - macro- and microstructure,stability, " - and rheological properties - separately. Molecular modelling of such emulsions, studying the simultaneous effects of polydispersity and drop distortion on max for various packing types, has been carried out by Das et al ... 

Dimer acid, hydrogenated surfactant, household automatic dishwashing detergents... 

Schubert and Kaler [128] have shown that microemulsions of a variety of fluorinated oils in water can be made by using a mixture of a fluorinated surfactants and a nonionic hydrogenated surfactant. The relative amount and chain... 

The electrochemical behavior of fluorinated surfactants at gold electrodes [106-108], platinum [109], and mercury [109] electrodes has been studied and compared with that of hydrogenated surfactants. 

---