Alcohols nonionic hydrophobes

Surfactants employed for w/o-ME formation, listed in Table 1, are more lipophilic than those employed in aqueous systems, e.g., for micelles or oil-in-water emulsions, having a hydrophilic-lipophilic balance (HLB) value of around 8-11 [4-40]. The most commonly employed surfactant for w/o-ME formation is Aerosol-OT, or AOT [sodium bis(2-ethylhexyl) sulfosuccinate], containing an anionic sulfonate headgroup and two hydrocarbon tails. Common cationic surfactants, such as cetyl trimethyl ammonium bromide (CTAB) and trioctylmethyl ammonium bromide (TOMAC), have also fulfilled this purpose however, cosurfactants (e.g., fatty alcohols, such as 1-butanol or 1-octanol) must be added for a monophasic w/o-ME (Winsor IV) system to occur. Nonionic and mixed ionic-nonionic surfactant systems have received a great deal of attention recently because they are more biocompatible and they promote less inactivation of biomolecules compared to ionic surfactants. Surfactants with two or more hydrophobic tail groups of different lengths frequently form w/o-MEs more readily than one-tailed surfactants without the requirement of cosurfactant, perhaps because of their wedge-shaped molecular structure [17,41]. 

There have been few studies of the properties of pure compounds in these series of nonionics (5, 6). In our laboratory, the nonionics shown in Table IV and V have been synthesized by the addition of ethylene oxide under the same conditions to pure ethylene glycol monoethers, rather than to secondary or tertiary alcohols. This method has been found to give the same Poisson distribution of OE units and to be suitable for evaluating quantitatively the structural effects of the hydrophobe (7 ). 

This paper will review the biodegradation of nonionic surfactants. The major focus will be on alcohol ethoxylates and alkylphenol ethoxylates—the two largest volume nonionics. In this paper the effect of hydrophobe structure will be discussed, since hydrophobe structure is considered more critical than that of the hydrophile in biodegradability of the largest volume nonionics. The influence of the hydrophobe on the biodegradation pathway will be examined with an emphasis on the use of radiolabeled nonionics. 

In tile application of surfactants, physical and use properties, precisely specified, are of primary concern. Chemical homogeneity is of little significance in practice. In fact, surfactants are generally polydisperse mixtures, such as the natural fats as precursors of fatty acid-derived surfactant structures e.g., coconut oil contains glycerol esters of Cc-Qa fatly acids. Nonionic surfactants of die alcohol edioxylate type are polydisperse not only with respect to the hydrophobe but also in the number of edivlene oxide units attached. 

This chapter describes recent work in our laboratories examining density modification of DNAPLs through a combination of batch non-equilibrium rate measurements and DNAPL displacement experiments in 2D aquifer cells. The objective of this work was to evaluate the applicability of nonionic surfactants as a delivery mechanism for introducing hydrophobic alcohols to convert the DNAPL to an LNAPL prior to mobilizing the NAPL. Three different nonionic surfactants were examined in combination with n-butanol and a range of DNAPLs. Overall, it was found that different surfactants can produce dramatically different rates of alcohol partitioning and density modification. However, for some systems interfacial tension reduction was found to be a problem, leading to unwanted downward... 

Capek described the use of a macromonomer in miniemulsion polymerization [54]. Lim and Chen used polyfmethyl methacrylate-fr-(diethylamino)ethyl methacrylate) diblock copolymer as surfactant and hexadecane as hydrophobe for the stabilization of miniemulsions [55]. Particles with sizes between about 150 and 400 nm were produced. It is possible to create stable vinyl acetate miniemulsions employing nonionic polyvinyl alcohol (PVA) as surfactant and hexadecane as hydrophobe [56]. 

Surfactants. Ethylene oxide-containing surfactants are generally of nonionic or anionic classes. The nonionic materials are made by base-catalyzed addition of ethylene oxide to either fatty alcohols or alkylphenols. Sulfation can be used to convert these compounds to the sulfated anionic surfactants. The products contain from a few to many ethylene oxide molecules per alcohol. The chain of polyethylene oxide) in a nonionic product acts as the hydrophile, and the alkyl or alkaryl residue is the hydrophobe. A sulfate salt group adds to the hydrophilicity of an anionic surfactant. 

Determinations of the adsorption isotherms for a number of organic solvent-water systems in contact with hydrocarbonaceous stationary phases have shown that a layer of solvent molecules forms on the bonded-phase surface and that the extent of the layer increases with the concentration of the solvent in the mobile phase. For example, methanol shows a Langmuir-type isotherm when distributed between water and Partisil ODS (56). This effect can be exploited to enhance the resolution and the recoveries of hydrophobic peptides by the use of low concentrations, i.e., <5% v/v, of medium-chain alkyl alcohols such as tm-butanol or tert-pentanol or other polar, but nonionic solvents added to aquo-methanol or acetonitrile eluents. It also highlights the cautionary requirement that adequate equilibration of a reversed-phase system is mandatory if reproducible chromatography is to be obtained with surface-active components in the mobile phase. 

With long-chain hydrocarbons, such as oil, where hydrophobic and hydrophilic portions of the molecule exist, surface-tension effects will be significant, and may result in foaming and possible acceleration of carryover. The alkalinity of the boiler water may saponify any fatty acids present, producing a crude soap that may foam. Soaps, sulfated oils and alcohol, sulfonated aliphatics and aroma.ics, quaternary ammonium compounds, nonionic organic ethers and esters, and various fine particles, act as emulsifiers that can increase foaming. 

Nonionic surfactants are one of the most important and largest surfactant groups. They are amphiphilic molecules composed, in most cases, of poly(ethylene oxide) (PEO) blocks as the water-soluble fragment and fatty alcohols, fatty acids, alkylated phenol derivatives, or various synthetic polymers as the hydrophobic part [1], This class of surfactants is widely used as surface wetting agents, emulsifiers, detergents, phase-transfer agents, and solubilizers for diverse industrial and biomedical applications [2],... 

Nonionic, anionic, and cationic VP copolymers are all available commercially to enhance the hydrophilic, hydrophobic, and ionic properties of PVP for specihc applications. Important comonomers include vinyl acetate (VA), acrylic acid (AA), vinyl alcohol, dimethy-laminoethylmethacrylate (DMAEMA), styrene, maleic anhydride, acrylamide, methyl methacrylate, lauryl methacrylate (LM), a-olelins, methacrylamido-propyltrimethyl ammonium chloride (MAPTAC), vinyl caprolactam (VCL), and dimethylaminopropyl-methacrylamide (DMAPMA). 

Polymers are also essential for the stabilisation of nonaqueous dispersions, since in this case electrostatic stabilisation is not possible (due to the low dielectric constant of the medium). In order to understand the role of nonionic surfactants and polymers in dispersion stability, it is essential to consider the adsorption and conformation of the surfactant and macromolecule at the solid/liquid interface (this point was discussed in detail in Chapters 5 and 6). With nonionic surfactants of the alcohol ethoxylate-type (which may be represented as A-B stmctures), the hydrophobic chain B (the alkyl group) becomes adsorbed onto the hydrophobic particle or droplet surface so as to leave the strongly hydrated poly(ethylene oxide) (PEO) chain A dangling in solution The latter provides not only the steric repulsion but also a hydrodynamic thickness 5 that is determined by the number of ethylene oxide (EO) units present. The polymeric surfactants used for steric stabilisation are mostly of the A-B-A type, with the hydrophobic B chain [e.g., poly (propylene oxide)] forming the anchor as a result of its being strongly adsorbed onto the hydrophobic particle or oil droplet The A chains consist of hydrophilic components (e.g., EO groups), and these provide the effective steric repulsion. 

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. 

PVP is a nonionic water-soluble polymer that interacts with water-soluble dyes to form water-soluble complexes with less fabric substantivity than the free dye. Additionally, PVP inhibits soil redeposition and is particularly effective with synthetic fibers and synthetic cotton blends. The polymer comprises hydrophilic, dipolar imido groups in conjunction with hydrophobic, apolar methylene and methine groups. The combination of dipolar and amphiphilic character make PVP soluble in water and organic solvents such as alcohols and partially halogenated alkanes, and will complex a variety of polarizable and acidic compounds. PVP is particularly effective with blue dyes and not as effective with acid red dyes. 

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