Surfactants without additives

Figure 14.1a shows aj vs. U curve in Cu + Sn + H2SO4 with (solid curve) and without (dashed curve) cationic surfactant. The addition of the surfactant causes a drastic change in they vs. U curve. Namely, an NDR appears in a narrow potential region of about 5 mV near —0.42 V, where the Cu-Sn alloy is electrodeposited. Another notable point in the surfactant-added solution is that a current oscillation appears when the Uis kept constant in (and near) the potential region of this NDR, as shown in Figure 14.1b. It was also revealed that both the NDR and current oscillation appeared only in the presence of cationic surfactant and not in the presence of anionic surfactant.

The experimental evaluation [4] of the stability of non-ionic surfactants (nonylphenol ethoxylates, NPEOs, and alcohol ethoxylates, AEOs) during sample storage showed that aqueous samples can be stored at 4°C without addition of any preservative only for a short time (a maximum of 5 days). The most often used preservative is formaline (1-8% (v/v) of 37% solution of formaldehyde in water). 

Fig.5 XRD patterns of MCM-41 samples synthesized with Cm and Cis surfactants without any additional cation (a) and (b), and with TPA+ as additional cation (c) and (d). Calcined samples (a) and (c), water-treated samples (b) and (d).

The pore size distributions of Ti-MCM-41 synthesized in this work are shown in Fig. 2. All of the samples showed a sharp distribution without addition of TMB and the use of methanol solvent resulted in the expansion of pore channel size. The average pore sizes determined by N, adsorption were 4.0nm and 2.8nm when the added solvents were methanol and ethanol, respectively. In this case, the used surfactant was C22TMAC1. In addition, the expansion of BJH pore size of Ti-MCM-41 was observed by the addition of TMB. A broad pore size distribution was investigated by using TMB as an auxiliary chemical. The mean pore size was ca. 7.5nm in methanol solvent. 

Ti-MCM-41 could be synthesized within 4 hours with a high crystallinity by the evaporation method and the pore size could be controlled by addition of TMB in this work. The TEM image of Ti-MCM-41 which was obtained in the presence of TMB indicates the regular and expanding pore arrangements. The purely siliceous MCM-41 sample was also synthesized and used to immobilize the chiral salen complexes as in Scheme 1, which was synthesized without addition of Ti source by the same method as adopted for Ti-MCM-41 using a C22TMAC1 surfactant in methanol solvent without addition of TMB. 

Fell et al. presented a micellar two-phase system in which fatty acid esters can be hydroformylated [30]. Short fatty acids react in a mixture of water and the substrate without adding any surfactants. The rhodium/NaTPPTS catalyst system was able to conduct the reaction of methyl 10-undecenoate at 100°C with 30-bar synthesis gas pressure with a conversion of 99% without any surfactant. The reaction of linolenic acid ester was hindered by phase transfer problems which could be overcome by employing surfactants. The addition decreased the reaction time, so the same rhodium catalyst could achieve a conversion for linolenic methyl ester of 100%. The authors... 

Natural surfactants such as sodium taurocholate and sodium glycocholate are not able to eliminate the limiting character of the aqueous diffusion layer adjacent to the luminal side of the membrane [29, 30]. For that reason in the presence of these natural surfactants at their CMC, the absorption Hpophihdty correlations are as hyperbolic as the ones obtained without additives. Figure 4.3 displays the difference between the correlations obtained in the presence of polysorbate 80 and sodium taurocholate [27, 28]. 

Aqueous solutions of surfactants (micellar and nonmicellar) without additives or with water soluble nonelectrolytes as additives... 

Figure 2 clearly indicates that a captan wettable powder containing approximately 55% captan, 33% clay, 11% dispersant, and 1% surfactant should be evaluated if maximum suspensibility is desired. In addition to indicating regions of optimal composition, response-surface maps are extremely useful in analyzing cost vs. performance. Questions such as, "What is the most economical formulation that has 60% suspensibility " may be answered objectively, without additional experimentation. 

The surfactant AOT forms reverse micelles in non-polar fluids without addition of a cosurfactant, and thus it is possible to study simple, water/AOT/oil, three component systems. To determine micelle structure and behavior in water/AOT/oil systems, investigators have studied a wide range of properties including conductivity (15), light (JL ), and neutron (12) scattering, as well as solution phase behavior (1 ). From information of this type one can begin to build both microscopic models and thermodynamic... 

Extraction with solvent has less influence on product pore-structure. The common solvents used include ethanol, methanol, and water. To remove cationic surfactant more efficiently, HC1 is added in the solvent. The surfactant recovered can be reused. Nonionic surfactant can be extracted easily, even without addition of HC1. The removal of surfactant with solvent extraction can be combined with modification of the product. 

Several procedures for a one-pot Mannich-type reaction in water to give (3-amino carbonyl compounds catalyzed by either Lewis acid or Bronsted acid with or without addition of surfactants have been developed. The reactions are high yielding however, the diastereoselectivities are moderate. The HBF4-catalyzed reaction between aldimines and ketene silyl acetals in a water/SDS mixture provides high stereoselectivity with very good yields (Scheme 5.19). 

In practice, a thin film of oily soil can often form on the hair surface with a contact angle of zero. In this case, it may not be possible for a surfactant to roll back completely the hydrophobic soil without additional mechanical action such as rubbing and flexing. 

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