Alkyl ether nonionic surfactants, polyoxyethylene

The behavior of a series of polyoxyethylene alkyl ether nonionic surfactants is also illustrative. According to Figure 11 the dioxyethylene (A) compound does not form liquid crystals when combined with water. Its solutions with decane dissolve water only in proportion to the amount of emulsifier. The tetraoxyethylene dodecyl ether (B) forms a lamellar liquid crystalline phase and is not soluble in water but is completely miscible with the hydrocarbon. The octaoxyethylene compound (C) is soluble in both water and in hydrocarbon and gives rise to three different liquid crystals a middle phase, an isotropic liquid crystal, and a lamellar phase containing less water. If the hydrocarbon p-xylene is replaced by hexadecane (D), a surfactant phase (L) and a lamellar phase containing higher amounts of hydrocarbon are formed in combination with the tetraoxyethylene compound (B-D). 

Zech et al. [90] reported high-temperatiue-stable microemttlsions composed of the room-temperature IL EAN as polar phase. Byrne et al. [91] reported on the solubility of HEWL in aqueous EAN as a function of water content. The structure of micelles formed by nonionic polyoxyethylene alkyl ether nonionic surfactants in the room-temperatrrre IL EAN by small-angle neutron scattering as a function of alkyl and ethoxy chain length, concentration, and temperatrrre, was reported by Araos et al. [92]. 

Berthod, A. Tomer, S. and Dorsey, J. G. (2001). Polyoxyethylene alkyl ether nonionic surfactants physicochemical properties and use for cholesterol determination in food. Talanta, 55,1, 69-83. 

The most common surfactants for analytical applications are nonionic (polyoxyethylene glycol monoethers, polyoxyethylene methyl- -alkyl ethers, t-octylphenoxy polyoxyethylene ethers, and polyoxyethylene sorbitan esters... 

Phase diagrams of water, hydrocarbon, and nonionic surfactants (polyoxyethylene alkyl ethers) are presented, and their general features are related to the PIT value or HLB temperature. The pronounced solubilization changes in the isotropic liquid phases which have been observed in the HLB temperature range were limited to the association of the surfactant into micelles. The solubility of water in a liquid surfactant and the regions of liquid crystals obtained from water-surfactant interaction varied only slightly in the HLB temperature range. 

Stancher, B., and L. Favretto. 1978. Gas-liquid chromatograpJiic fractionation of polyoxyethylene nonionic surfactants—Polyoxyethylene mono-n-alkyl ethers. ]. Chromatogr. 150, 447-453. 

Therefore, the hypothesis of an increasing nonionic character of alkyl ether sulfates with increasing number of oxyethylene groups is not tenable. Some time ago (30), it was suggested that a certain hydrophobic nature can be attributed to the polyoxyethylene chain of alkyl ether sulfates. At first, this appears to be in contradiction to the decidedly hydrophilic character of the polyoxyethylene chain for nonionic surfactants. However, the possibility of EO group hydration impairment by the sulfate group cannot be excluded. 

The difficulty with HLB as an index of physicochemical properties is that it is not a unique value, as the data of Zaslavsky et al. (1) on the haemolytic activity of three alkyl mercaptan polyoxyethylene derivatives clearly show in Table 1. Nevertheless data on promotion of the absorption of drugs by series of nonionic surfactants, when plotted as a function of HLB do show patterns of behaviour which can assist in pin-pointing the necessary lipophilicity required for optimal biological activity. It is evident however, that structural specificity plays a part in interactions of nonionic surfactants with biomembranes as shown in Table 1. It is reasonable to assume that membranes with different lipophilicities will"require" surfactants of different HLB to achieve penetration and fluidization one of the difficulties in discerning this optimal value of HLB resides in the problems of analysis of data in the literature. For example, Hirai et al. (8 ) examined the effect of a large series of alkyl polyoxyethylene ethers (C4,C0, Cj2 and C 2 series) on the absorption of insulin through the nasal mucosa of rats. Some results are shown in Table II. 

A plot of the temperatures required for clouding versus surfactant concentration typically exhibits a minimum in the case of nonionic surfactants (or a maximum in the case of zwitterionics) in its coexistence curve, with the temperature and surfactant concentration at which the minimum (or maximum) occurs being referred to as the critical temperature and concentration, respectively. This type of behavior is also exhibited by other nonionic surfactants, that is, nonionic polymers, // - a I k y I s u I Any lalcoh o I s, hydroxymethyl or ethyl celluloses, dimethylalkylphosphine oxides, or, most commonly, alkyl (or aryl) polyoxyethylene ethers. Likewise, certain zwitterionic surfactant solutions can also exhibit critical behavior in which an upper rather than a lower consolute boundary is present. Previously, metal ions (in the form of metal chelate complexes) were extracted and enriched from aqueous media using such a cloud point extraction approach with nonionic surfactants. Extraction efficiencies in excess of 98% for such metal ion extraction techniques were achieved with enrichment factors in the range of 45-200. In addition to metal ion enrichments, this type of micellar cloud point extraction approach has been reported to be useful for the separation of hydrophobic from hydrophilic proteins, both originally present in an aqueous solution, and also for the preconcentration of the former type of proteins. 

Furthermore, aggregates of nonionic surfactants like polyoxyethylene alkyl/aryl ethers of the Tergitol, Triton, and Brij series were used as templates for the formation of mesoporous silica materials in neutral or acidic media. The pore diameters of the materials that can be obtained with these surfactants are restricted to around 5.5 nm. The advantages of these surfactants over triblock copolymers are that they are cheap, nontoxic, and biodegradable. An overview of the most commonly used SDAs is compiled in Table 3.1. 

Stability The technique and results of stability experiments were described explained in an earlier paper [I ]. In brief, a series of conunercially available homologous nonionic surfactants of the polyoxyethylene alkyl ether type and two nonionic surfactants were examined for their ability to affect the CMP process with respect to enhancing slurry stability. The salient features of the stability study are incorporated in the following discussion. 

Polyoxyethylene alkyl ethers are nonionic surfactants produced by the polyethoxylation of linear fatty alcohols. Products tend to be mixtures of polymers of slightly varying molecular weights and the numbers used to describe polymer lengths are average values. 

Polyoxyethylene alkyl ethers are nonionic surfactants widely used in topical pharmaceutical formulations and cosmetics, primarily as emulsifying agents for water-in-oil and oil-in-water emulsions and the stabilization of microemulsions and multiple emulsions. 

Polyoxyethylene alkyl ethers are used as nonionic surfactants in a variety of topical pharmaceutical formulations and cosmetics. The polyoxyethylene alkyl ethers form a series of materials with varying physical properties and manufacturers literature should be consulted for information on the applications and safety of specific materials. 

A combination of SLS and DLS methods was used to investigate the behavior of nonionic micellar solutions in the vicinity of their cloud point. It had been known for many years that at a high temperature the micellar solutions of polyoxyethylene-alkyl ether surfactants (QEOm) separate into two isotropic phases. The solutions become opalescent with the approach of the cloud point, and several different explanations of this phenomenon were proposed. Corti and Degiorgio measured the temperature dependence of D pp and (Ig), and found that they can be described as a result of critical phase separation, connected with intermicellar attraction and long-range fluctuations in the local micellar concentration. Far from the cloud point, the micelles of nonionic surfactants with a large number of ethoxy-groups (m 30) may behave as hard spheres. ... 

Surfactants Nonionic Sorbitan esters Polysorbates Polyoxyethylene alkyl ethers Polyoxyethylene alkyl esters Polyoxyethylene aryl ethers Glycerol esters Cholesterol Anionic Sodium dodecyl sulphate Cationic Cetrimide Benzalkonium chloride... 

Nonionic surfactants such as polyoxyethylated fatty alcohols (such as Emul-phor ON-870 from GAP), alkyl phenyl polyethylene glycol ethers (such as the Tergitols from Union Carbide) and polyoxyethylated octylphenol may be used as protective colloids along with anionic surfactants or, in some cases, as emulsifiers in their own right. The block copolymers of polyoxyethylene and polyoxypropylene (Pluronics) solubilized vinyl acetate. Polymerization takes place at the interface of the surfactant-monomer droplet and the aqueous phase [151]. 

Kunieda s group reported numerous viscoelastic worm-like micellar systems in the salt-free condition when a lipophilic nonionic surfactant such as short hydrophilic chain poly(oxyethylene) alkyl ether, C EOni, or N-hydroxyethyl-N-methylaUcanolamide, NMEA-n, was added to the dilute micellar solution of hydrophilic cationic (dodecyltrimethylammonium bromide, DTAB and hexade-cyltrimethylammonium bromide, CTAB) [12-14], anionic (sodium dodecyl sulfate, SDS [15, 16], sodium dodecyl trioxyethylene sulfate, SDES [17], and Gemini-type [18]) or nonionic (sucrose alkanoates, C SE [9, 19], polyoxyethylene cholesteryl ethers, ChEO [10, 20], polyoxyethylene phytosterol, PhyEO [11, 21] and polyoxyethylene sorbitan monooleate, Tween-80 [22]) surfactants. The mechanism of formation of these worm-Hke stmctures and the resulting rheological behavior of micellar solutions is discussed in this section based in some actual published and unpublished results, but conclusions can qualitatively be extended to aU the systems studied by Kunieda s group. 

Materials that are solubilized in polyethylene glycol can be solubilized in the polyoxyethylene chains on the surface of a nonionic micelle. Ismail, Gouda, and Motawi found that the micellar partition coefficients of barbiturates in polysorbates 20, 40, 60, and 80 is a function of the solute substituents and is proportional to the octanol-water partition coefficient of the barbiturate. Similarly, Ikeda, Kato, and Tukamoto showed that the solubilization of alkyl barbiturates by polyoxyethylene lauryl ether is not dependent upon the number of carbons in the substituents. Since the different polysorbates contain different aliphatic groups, the rather small dependence of solubilization upon polysorbate number (i.e., upon alkyl chain length) suggests that the barbiturates are not solubilized primarily in the hydrocarbon portion of the micelle. Gouda, Ismail, and Motawi showed that the solubilization of barbiturates in polyoxyethylene stearates is proportional to the number of polyoxyethylene units in the surfactant. 

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