Anionic surfactants characterization

Three generations of latices as characterized by the type of surfactant used in manufacture have been defined (53). The first generation includes latices made with conventional (/) anionic surfactants like fatty acid soaps, alkyl carboxylates, alkyl sulfates, and alkyl sulfonates (54) (2) nonionic surfactants like poly(ethylene oxide) or poly(vinyl alcohol) used to improve freeze—thaw and shear stabiUty and (J) cationic surfactants like amines, nitriles, and other nitrogen bases, rarely used because of incompatibiUty problems. Portiand cement latex modifiers are one example where cationic surfactants are used. Anionic surfactants yield smaller particles than nonionic surfactants (55). Often a combination of anionic surfactants or anionic and nonionic surfactants are used to provide improved stabiUty. The stabilizing abiUty of anionic fatty acid soaps diminishes at lower pH as the soaps revert to their acids. First-generation latices also suffer from the presence of soap on the polymer particles at the end of the polymerization. Steam and vacuum stripping methods are often used to remove the soap and unreacted monomer from the final product (56). 

Thin-layer chromatography (TLC) is used both for characterization of alcohol sulfates and alcohol ether sulfates and for their analysis in mixtures. This technique, combined with the use of scanning densitometers, is a quantitative analytical method. TLC is preferred to HPLC in this case as anionic surfactants do not contain strong chromophores and the refractive index detector is of low sensitivity and not suitable for gradient elution. A recent development in HPLC detector technology, the evaporative light-scattering detector, will probably overcome these sensitivity problems. 

A wide range of anionic surfactants (Fig. 23) has been classified into groups, including alkyl benzene sulfonates (ABS), linear alkyl benzene sulfonates (LAS), alcohol sulfates (AS), alcohol ether sulfates (AES), alkyl phenol ether sulfates (APES), fatty acid amide ether sulfates (FAES), alpha-olefin sulfates (AOS), paraffin sulfonates, alpha sulfonated fatty acids and esters, sulfonated fatty acids and esters, mono- and di-ester sulfosuccinates, sulfosuccinamates, petroleum sulfonates, phosphate esters, and ligno-sulfonates. Of the anionic surfactants, ABS and LAS continue to be the major products of anionic surfactants [314, 324]. Anionic surfactants have been extensively monitored and characterized in various environmental matrices [34,35,45,325-329]. 

Complexes of the [Ru(bpy)2L] " type in which L is a phen-based ligand are discussed next. Perchlorate salts of [Ru(bpy)2(phen)] + and [Ru(bpy)2(5-Mephen)] + have been prepared and structurally characterized. The steric strain within the coordination sphere is relieved in part by twisting of each bpy ligand. Time-resolved resonance Raman spectroscopy has been used to investigate the localization of the excited electron in the MLCT state of [Ru(bpy)2(4,7-Ph2-phen)] In neutral micelles, the electron is localized on the bpy ligands, but in the presence of DNA and anionic surfactants, it is localized on 4,7-Ph2phen when the complex is in aqueous... 

The same principle may be extended to characterize mixtures of surfactants. If the case of anionic surfactants is still taken as an example, and if... 

Characterization of the polymer indicates that an application of sodium dodecyl sulfonate as anionic surfactant and sodium persulfate as initiator for both stages leads to a hemisphere particle... 

A preparation in two steps has been chosen hrst a new hybrid silica precursor P-CDAPS, containing P-CD groups and amine functions, has been prepared and characterized. Then, this precursor has been co-condensed with tetraethyl orthosilicate (TEOS) via a sol-gel process involving the use of surfactant. We chose the anionic surfactant sodium dodecylsulfate (SDS). The chemical and structural characterization combined with adsorption tests of p-nitrophenol and lead nitrate led to the evaluation of the accessibility and the effectiveness of the binding functions in these hybrid materials. 

Hybrid silica materials were prepared via a sol-gel pathway at pH 9. The influence of anionic surfactant (SDS) was studied by comparing templated materials (TbSn series) with hybrid materials obtained without surfactant (Tbn series). Two mechanisms of mesostructure formation can be considered as represented on Fig. 2. The pka of aminopropyl chain is about 10.6 in the reaction mixture propyl-amines are partially protonated. Electrostatic interactions between dodecylsulfate anion and NH and sodium cation neutralization may then occur, resulting in the condensation of the silica structure around surfactant micelles and aminopropyl groups at the surface of the pores. The other mechanism is SDS chains complex-ation by P-CD cavity, which wonld result in P-CD gronps located at the surface of the pores and aminopropyl less accessible, due to steric hindrance caused by P-CD bulky groups. A complete characterization of the prodncts and adsorption capacities will help nnderstanding the formation mechanism of mesoporons hybrid silica. 

Cuzzola et al. [25-26] identified and characterized Fenton oxidation products of lauryl sulfate and AES. The Fenton reaction is a frequently applied oxidative treatment in STPs. The degradation prodncts of anionic surfactants have been objects of stndy as well, because their biodegradation products might involve the loss of the snlfate group, resulting in essentially nonionic surfactants (see below). According to Schroder [27], the biodegradation of nonylphenol ethoxy sulfates does not involve a loss of the sulfate. 

The spectroscopic probe pyridine-N-oxide was used to characterize polar microdomains in reverse micelles in supercritical ethane from 50 to 300 bar. For both anionic and nonionic surfactants, the polarities of these microdomains were adjusted continuously over a wide range using modest pressure changes. The solubilization of water in the micelles increases significantly with the addition of the cosolvent octane or the co-surfactant octanol. Quantitative solubilities are reported for the first time for hydrophiles in reverse micelles in supercritical fluids. The amino acid tryptophan has been solubilized in ethane at the 0.1 wt.% level with the use of an anionic surfactant, sodium di-2-ethylhexyl sulfosuccinate (AOT). The existence of polar microdomains in aggregates in supercritical fluids at relatively low pressures, along with the adjustability of these domains with pressure, presents new possibilities for separation and reaction processes involving hydrophilic substances. 

Mohamed, M.M. et al.. Synthesis and structural characterization of TiO2 and V2O5/ TiO2 nanoparticles assembled by the anionic surfactant sodium dodecyl sulfate, Micropor. Mesopor. Mater, 97, 66, 2006. 

Special examples of mixture adsorption are competitive adsorption of the different forms of the same substance, such as pH-dependent ionic and undissociated molecular forms, monomers, and associates of the same substance, as well as potential-dependent adsorption of the same compound in two different orientations in the adsorbed layer. Different orientations on the electrode surface—for example, flat and vertical—are characterized with different adsorption constants, lateral interactions, and surface concentrations at saturation. If there are strong attractive interactions between the adsorbed molecules, associates and micellar forms can be formed in the adsorbed layer even when bulk concentrations are below the critical micellar concentration (CMC). These phenomena were observed also at mineral oxide surfaces for isomerically pure anionic surfactants and their mixtures and for mixtures of nonionic and anionic surfactants (Scamehorn et al., 1982a-c). 

Fig. 3.18 shows a typical force curve for an aqueous solution of an anionic surfactant and an alcohol (weight composition 7.2% sodium dodecyl sulfate, 17.5% 1-pentanol, 75.3% water), that forms a lamellar smectic A phase at room temperature and alignes homeotropically on bare mica [43]. The structural force is characterized by periodic damped oscillations, with... 

Huang, R.Y.M., Moon, G.Y. and Pal, R. 2001. Chitosan/anionic surfactant complex membranes for the pervaporation separation of methanoPMTBE and characterization of the polymer/surfactant system, 184 1-15. 

Inductively coupled plasma-atomic emission spectrometry allows the determination of anionic surfactants (LAS and AS) and inorganic compounds (phosphate, silicate, zeolite, sulfate). Other techniques, such as X-ray fluorescence spectroscopy and X-ray powder diffraction, have been used for the qualitative analysis of inorganic detergents. For surface analysis, optical light microscopy, scanning electron microscopy, and transmission electron microscopy characterize particles, deposition of surfactant, or other detergent ingredients on fabric. 

Amphoteric surfactants are characterized by a molecular structure containing two different fnnc-tional groups, with anionic and cationic characters, respectively [19]. Most amphoteric surfactants are able to behave like cationic snrfactants in acidic medinm, and like anionic surfactants in alkaline medium. However, betaines are different in that they cannot be forced to assume anionic active behavior through an increase in the pH valne [20,21]. Fignre 12.7 shows strnctnres of the most widely nsed amphoteric surfactants, as prodnced, in dependence of the pH valne. 

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