Surfactant decane

Figure 9. 13C, II-decoupled NMR spectra of surfactant-decane samples. The sample with 82 wt % surfactant was produced by equilibrating surfactant crys-tallites with decane vapor.

An hour after the 7.7 wt% sample was cooled back down it looked as clear as at 65°C. However, Spectrum 17 shows that the surfactant molecules were no longer mobile. Evidently they had formed a phase dispersed into units so small — no larger than several hundred Angstroms, probably — that there was no visible scattering. After weeks of standing only a bit of white precipitate appeared, a small fraction of the total surfactant present. It follows that the growth of some of the submicro-scopic units to visible, settling size was the slow step in the subsequent precipitation of the surfactant-decane phase. 

Surfactant solubility in decane was 0.04 wt% at 25°C and about 9 wt% at 50°C. The surfactant-rich phase in equilibrium with isotropic decane solution was birefringent. About 20 wt% decane was vapor-sorbed by dry surfactant at 25°C. Preliminary polarizing microscopy and nmr results point toward the existence of liquid crystalline states in surfactant-decane and surfactant-decane-water systems. 

Figure 1 Relative viscosity r r 25°C as a function of the volume fraction 0 (of surfactant plus decane) for microemulsions of constant surfactant/decane molar ratio of 3.2 1. ( ) PureTDMAO (O) 7.5 mol% TTABr (O) 7.5 mol% SDS [solid lines fitted according to Eq. (10)]. (From Ref. 56.)...

Titanium alkoxides have been used by various workers as the source of titanium for the synthesis of Ti02 particles via microemulsions. In an early work reported by Guizard et al. [260] a reverse microemulsion was prepared by mixing Triton X-100 (surfactant), decane (oil phase) and water Ti-tetrabutoxide or tetraisopropoxide was added to it for precipitation of particles. 

Important work on microemulsion synthesis of silica nanoparticles has been carried out by Arriagada and Osseo-Asare (1995, 1999) using different systems like NaAOT (an anionic surfactant)/decane/benzyl alcohol/ammonia solution and TEOS the w value varied in the range 2.0-9.5. As pointed out above, low w values (less than 4 in this case) caused all the water to get bound to the surfactants, and no particles were obtained. With increased water content, spherical silica particles in the size range of 10-60 nm (depending on experimental conditions) were obtained. When the selected w value was 9 or more, stable microemulsions were not obtained. In a system like cyclohexane/NP-5 (a non-ionic surfactant)/ammonia solution and TEOS, on the other hand, low values of w ( 0.05-2.0) could cause formation of particles 40-60 nm in size when w increased to 5.5, the particle size increased to 75 nm. The general trend was, thus, an increase in the particle size with increase in w when other conditions remained the same. 

The HLB numbers decrease with increasing chain length, e.g., from 13.25 for sodium decane 1-sulfonate to 9.45 for the C18 homolog [72]. Typical HLB numbers for positional isomers range from 12.3 for sodium dodecane 1-sulfonate to 13.2 for the more hydrophilic 6 isomer [73]. The HLB numbers of alkanesulfonates are less influenced by the isomeric position of the functional group and by substituents than the cM values [68]. HLB numbers can be correlated with partition coefficients for the distribution of a surfactant between the aqueous and oily phases, which emphasizes that the partition coefficient is dependent on the carbon number [68]. 

Comparison of the IFT results for AOS 1618 samples in entries 2 and 9 indicate that the minor differences in di monosulfonate ratio of these AOS surfactants (entries 1 and 2 in Table 10) would have little effect on deionized water IFT values against decane. 

The contemporaneous presence of different solubilizates sometimes involves competition for the micellar binding sites [31], For instance, from an analysis of the heats of solution of benzene and water in solutions of reversed micelles of tehaethylene glycol dodecyl ether in decane, a competition between water and benzene for the surfactant hydrophilic groups was shown [32],... 

The B. licheniformis JF-2 strain produces a very effective surfactant under conditions typical of oil reservoirs. The partially purified biosurfactant from JF-2 was shown to be the most active microbial surfactant found, and it gave an interfacial tension against decane of 0.016 mN/m. An optimal production of the surfactant was obtained in cultures grown in the presence of 5% NaCl at a temperature of 45° C and pH of 7. TTie major endproducts of fermentation were lactic acid and acetic acid, with smaller amounts of formic acid and acetoin. The growth and biosurfactant formation were also observed in anaerobic cultures supplemented with a suitable electron acceptor, such as NaNO3[1106]. 

EFFECT OF OIL. Titrations were performed in which small amounts of decane were added with the surfactant sample. The results were found to be insensitive to the presence of up to 2 cm3 of the decane. This allows the application of the method to both simple aqueous solutions and microemulsions containing significant quantities of decane. 

Ehase Inversion Temperatures It was possible to determine the Phase Inversion Temperature (PIT) for the system under study by reference to the conductivity/temperature profile obtained (Figure 2). Rapid declines were indicative of phase preference changes and mid-points were conveniently identified as the inversion point. The alkane series tended to yield PIT values within several degrees of each other but the estimation of the PIT for toluene occasionally proved difficult. Mole fraction mixing rules were employed to assist in the prediction of such PIT values. Toluene/decane blends were evaluated routinely for convenience, as shown in Figure 3. The construction of PIT/EACN profiles has yielded linear relationships, as did the mole fraction oil blends (Figures 4 and 5). The compilation and assessment of all experimental data enabled the significant parameters, attributable to such surfactant formulations, to be tabulated as in Table II. 

Host-guest systems made from dendritic materials have potential in the areas of membrane transport and drug delivery [68, 84, 85]. In a recent report [136] Tomalia and coworkers investigated structural aspects of a series of PAM AM bolaamphiphiles (e.g., 50) with a hydrophobic diamino do decane core unit. Fluorescence emission of added dye (nile red) was significantly enhanced in an aqueous medium in the presence of 50 unlike the cases when 51 and 52 were added (Fig. 23). Addition of anion surfactants to this mixture generated supramolecular assemblies which enhanced their ability (ca.by 10-fold) to accommodate nile red (53). Further increase in emission was noted by decreasing the pH from the normal value of 11 for PAMAM dendrimers to 7. At lower pH values the... 

The solubility of water is extremely low in hydrocarbons. For example, as low as 0.7% of water form the separate phase in decane (T = 298 K) [22], The surfactants create a small water micelle in hydrocarbon. For example, sodium bis-2-ethylhexyl sulfosuccinate (AOT) in the ratio H2O AOT = 20 creates stable micelles in decane with the diameter room temperature) [22]. The radii of a micelle r depends on the ratio H20 A0T the dependence has the following form [29] ... 

C] and 6% Cj g) was used as the anionic surfactant. Oleic Acid (Extra pure reagent, Kanto Chemical Co., Tokyo, Japan), Triolein (glycerol trioleate (Cj 2H33C00)3C3H5, Technical, BDH Chemicals, England) and n-decane (E. Merck, G.C., 95%) were used as oil. Sodium chloride (E. Merck, purity 100 0.05%) was used as electrolyte. 

Figure 3 shows the solubilization of triolein in Newcol surfactants. Figure 4 shows the solubilization of n-decane in the same surfactant solutions. The general characteristics of the curves in Figures 3 and 4 are the same as those shown in Figure 2. 

From the lower turbidity values shown in Figures 3 and 4, one may estimate that the solubilization of oleic acid is higher than triolein or n-decane in Newcol surfactant solutions. It is difficult to make further distinction between triolein and n-decane from Figures 3 and 4. 

Two main microemulsion microstructures have been identified droplet and biconti-nuous microemulsions (54-58). In the droplet type, the microemulsion phase consists of solubilized micelles reverse micelles for w/o systems and normal micelles for the o/w counterparts. In w/o microemulsions, spherical water drops are coated by a monomolecular film of surfactant, while in w/o microemulsions, the dispersed phase is oil. In contrast, bicontinuous microemulsions occur as a continuous network of aqueous domains enmeshed in a continuous network of oil, with the surfactant molecules occupying the oil/water boundaries. Microemulsion-based materials synthesis relies on the availability of surfactant/oil/aqueous phase formulations that give stable microemulsions (54-58). As can be seen from Table 2.2.1, a variety of surfactants have been used, as further detailed in Table 2.2.2 (16). Also, various oils have been utilized, including straight-chain alkanes (e.g., n-decane, /(-hexane),... 

Synthesis of CdS has been performed by using cyclohexane, isooctane or decane as the bulk solvent. The data are compared to those obtained with isooctane. Figure 3.4. shows the absorption onset and the CdS diameter obtained at various water contents, using Cd(N03) reactant (Fig. 3.4.4A and B) or functionalized surfactant Cd(AOT)2 (Fig. 3.4.4C and D). At low water content, w < 10, similar sizes are obtained, whatever bulk solvent is used. These indicate that for low water content, size control is not governed by exchange micellar rate but only by preparation mode and by the nature of ions in excess (Cd2+ or S2 ). 

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