Branched nonionic surfactants

NMR self-diffusion measurements indicated that all microemulsions consisted of closed water droplets and that the structure did not change much during the course of reaction. Hydrolysis was fast in microemulsions based on branched-chain anionic and nonionic surfactants but very slow when a branched cationic or a linear nonionic surfactant was employed (Fig. 11). The cationic surfactant was found to form aggregates with the enzyme. No such interactions were detected with the other surfactants. The straight-chain, but not the branched-chain, alcohol ethoxylate was a substrate for the enzyme. A slow rate of triglyceride hydrolysis for a Ci2E4-based microemulsion compared with formulations based on the anionic surfactant AOT [61,63] and the cationic surfactant cetyltrimethylammonium bromide (CTAB) [63] was observed in other cases also. Evidently, this type of lipase-catalyzed reaction should preferably be performed in a microemulsion based on an anionic or branched nonionic surfactant. Nonlipolytic enzymes such as cholesterol oxidase seem to function well in microemulsions based on straight-chain nonionic surfactants, however [64]. CTAB was reported to cause slow inactivation of different types of enzymes [62,64,65] and also, in the case of Chromobacterium viscosum lipase [66], to provide excellent stability. 

The primary application of these alcohols is the manufacture of anionic or nonionic surfactants for personal cleansing products, most of which end up in your wastewater treatment plants and rivers. Microorganisms don t chew up branch-chain surfactants as well as they do the straight ones. It used to be, for example that the surfactant based on the sodium salt of dodecyl benzene sulfonate, a 12-carbon branch chained anionic surfactant, was found to be slowing, down water treatment processes. Dodecyl alcohol as a raw material for these surfactants has been largely replaced by laurel alcohol, a 12-carbon straight-chain, linear alcohol. If you look at the bottle next time you shampoo your hair and rinse, you ll see sulfonates based on laurel alcohol listed, but none based on dodecyl. 

Another interesting feature of these CO2 evolution tests is that CO2 formation was still increasing for the linear alcohol ethoxylates but had reached a plateau for the branched nonionics. This suggests the formation of more bioresistant intermediates in the case of the branched surfactants. 

The single and double scan methods allow estimation of the value of the characteristic parameters for both ionic and nonionic surfactants (see Table 1). The extrapolation of Eqs. 8 and 9 to SACN = 0 allows the classification of the head groups in some hydrophihcity scale. Inspection of Table 1 data indicates that the branching and isomeric structure does have quite an influence on the characteristic parameter, as it has been reported in the Hter-ature [12,27-32]. 

Previous work has shown that binary surfactant systems containing Dowfax 8390 and the branched hydrophobic surfactant AOT can form Winsor III systems with both PCE and decane whereas DOWFAX 8390 by itself cannot (Wu et. al. 1999). This binary surfactant system was used in conjunction with hydrophobic octanoic acid to help with phase behavior and lessen the required concentration of CaCl2. Since this formulation is rather complicated, questions about field robustness arise. Thus, for the phase behavior studies presented here, we used the simple binary system of the nonionic TWEEN 80 and the branched hydrophobic AOT, and we optimized the NaCl concentration to give the Winsor Type III system. The lesser electrolyte concentration requirement for the binary TWEEN 80/ AOT system helps to decrease the potential for undesirable phase behavior such as surfactant precipitation, thereby increasing surfactant system robustness. 

Several nonionic surfactants, such as the alcohol ethoxylates, can also be used as wetting agents. These consist of a short hydrophobic chain (mostly Cjq) which is also branched, while a medium chain (PEO) mostly consisting of six EO units or lower may be used. These molecules also reduce the dynamic surface tension within a short time (<20 s), and have a reasonably low cmc. 

Frank, C., Frielinghaus, H., AUgaier, J. and Prast, H. (2007) Nonionic surfactants with linear and branched hydrocarbon tails Compositional analysis, phase behaviour, and film properties in bicontinuous microemulsions. Langmuir, 23, 6526-6535. 

The main nonionic surfactants are AEO, APEO, and recently APG. The hydrophobic part of AEO consists of n-alkanols with chain lengths between 8 and 20, typical AP are branched-chain octyl- or... 

On Figure 5 example high-pressure SANS data confirm the presence of spheroidal aggregates in sc COz- This provides further evidence for CO2 compatibility of these branched-chained, f-butyl-tipped nonionic surfactants. 

In works,the influence of cationic and nonionic surfactants, CTAB and PM on the reaction of phosphinate 12 with branched PEI-10 bearing o-hydroxybenzyl groups at the tertiary and secondary nitrogen (Scheme 15.3) in chloroform is investigated. The average... 

Whilst studies on linear alkyl surfactants are common, in recent years branched-chain nonionic surfactants have been studied as well as surfactants with novel head groups and surfactant mixtures. 

Oils are solubilized into the interior of micelles where they allow the micelle to swell to a larger radius, hence giving rise to cubic (12) and hexagonal (H2) phases at smaller a values than for the surfactant alone. Polar oils can also reside at the micelle surface to some extent, reducing micelle curvature and inducing the occurrence of lamellar and inverse phases. This behavior is typified by the behavior of the commercial nonionic surfactant nonylphenol-(probably branched)-decaethylene oxide with hexadecane and p-xylene [40]. 

A great variety of surfactants have been used in microemulsion formation. These include common soaps, other anionic and cationic surfactants, nonionic surfactants of the polyethylene oxide type, and other structures. The hydrophobic part contains one or two linear or branched hydrocarbon chains containing about 8-18 carbon atoms. Quite often microemulsions require, in addition to oil, water, and surfactant, the presence of simple electrolytes, alcohols, and/or other weakly surface-active substances. 

The nonionic surfactant characteristic is split into its ethylene oxide number tEON). i.e.. the average number of ethylene oxide groups per molecule, and the hydrophobe contribution OC. Only scarce data are available for a, which has a value near 6,6 and 6.1. respectively, for the branched nonyl and octyl phenol... 

Th is line exhibits a stair idtape that has been found to be typical of many systems, in the central region (e.g., 0.3 inversion line is essentially horizontal, while it exhibits two vertical branches on both extremes. It is fair remarking that this kind of inversion map wa.s mentioned in early work on the phase inversion temperature with nonionic surfactant systems (84). although the vertical branches were not entirely studied. 

Formulation can be specific to the crude oil emulsions such as was shown for Buchan crade by Mohammed et al. (67). They used nonionic surfactants from the Pluronic (PE) and Tetronic series, which differed basically in die degree of EO/POcopolymers added to straight chains or branches. In combination with wetting agents and octy- or... 

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