Poly Ethylene Glycol Monoalkyl Ethers Research Articles

The role of competitive counterion adsorption on the electrolyte induced surface ordering in methyl ester sulfonate surfactants at the air-water interface

The strong binding of Al3+ trivalent counterions to the anionic surfactants sodium polyethylene glycol monoalkyl ether sulfate and α-methyl ester sulfonate results in surface multilayer formation at the air-water interface. In contrast the divalent and monovalent counterions Ca2+ and Na+ result only in monolayer adsorption. Competitive counterion adsorption has been extensively studied in the context of surfactant precipitation and re-dissolution, but remains an important feature in understanding this surface ordering and how it can be manipulated.The α-methyl ester sulfonate surfactants are a promising class of anionic surfactants which have much potential for improved performance in many applications, greater tolerance to extreme solvent conditions such as water hardness, biocompatibility and sustainable production. Hence in this study we have used neutron reflectivity to extend previous studies on the surface ordering of the α-methyl ester sulfonate surfactant, sodium tetradecanoic 2-sulfo 1-methyl ester, in the presence of electrolyte to investigate the role of binary mixtures of electrolytes, AlCl3/CaCl2, and AlCl3/MgCl2.In the mixed electrolytes the evolution of the surface structure, from monolayer to multilayer with increasing AlCl3 concentration, is observed. It is broadly similar to that reported for the addition of only AlCl3. However with increasing CaCl2 concentration the structural evolution is shifted progressively to higher AlCl3 concentrations. Similar observations occur for the AlCl3/MgCl2 mixtures. However the presence of the MgCl2 results in an additional phenomenon; the partial co-adsorption of a more compact lamellar structure which exists until the highest AlCl3 concentrations. The results demonstrate the importance of the competitive adsorption of different counterions in driving and controlling the formation of surface multilayer structures with anionic surfactants. Furthermore it offers a facile route to the manipulation of these surface structures.

A simple and efficient ultrasonic-assisted extraction procedure combined with UV-Vis spectrophotometry for the pre-concentration and determination of folic acid (vitamin B9) in various sample matrices

ABSTRACTA simple and efficient ultrasonic-assisted extraction (UAE) procedure has been proposed for the pre-concentration of (2S)-2-[(4-{[(2-amino-4-hydroxypteridin-yl)methyl]amino}phenyl)formamido]pentanedioic acid (folic acid) in vegetables, pharmaceuticals and foods prior to determination at 540 nm using UV-Vis spectrophotometry. The method is based on hydrophobic ternary complex formation of folic acid with silver ions in the presence of cetyltrimethylammonium bromide (CTAB) as a sensitivity enhancer counter ion at pH 7.0, and then extraction into a micellar phase of polyethylene glycol monoalkyl ether (Genapol X-080). The impacts on the extraction efficiency and complex formation of analytical parameters such as sample pH, concentration of silver, concentration of surfactants and extraction time, ultrasonic time and sample volume, were investigated and optimised in detail. The matrix effect on the pre-concentration and determination of folic acid was investigated, and it was observed that the proposed method was highly selective against possible matrix co-extractives. Under optimised conditions, a good linear relationship between the analytical signal and folic acid concentration was obtained in the range of 0.6–180 μg l−1 with a detection limit of 0.19 μg l−1 and quantification limit of 0.63 μg l−1. The applicability was evaluated using samples fortified at different concentration levels, and recoveries higher than 94.1% were obtained. The precision as the percent relative standard deviation (RSD%) was in range of 2.5–3.8% (10 and 40 μg l−1, n = 5). The proposed method was validated by analysis of two standard reference materials (SRMs) and various real samples, and satisfactory results were obtained.

Impact of AlCl3 on the Self-Assembly of the Anionic Surfactant Sodium Polyethylene Glycol Monoalkyl Ether Sulfate in Aqueous Solution

Small-angle neutron scattering has been used to study the self-assembly of the anionic surfactant sodium polyethylene glycol monoalkyl ether sulfate in aqueous solution and in the presence of Al(3+) multivalent counterions in the form of AlCl3. The addition of the Al(3+) ions promotes significant micellar growth of the initially globular micelles into highly elongated structures until ultimately lamellar structures form. Increasing the size of the polyethylene oxide, EO, group progressively suppresses micellar growth before lamellar formation. Reducing the alkyl chain length has a similar effect on the structural evolution. Both trends are associated with increased solubility with increasing EO group size and decreasing alkyl chain length. Both the size of the EO group and the length of the alkyl chain affect sodium diethylene glycol monododecyl ether sulfate/Al(3+) complex formation and drive lamellar formation to progressively higher AlCl3 concentrations.

The Formation of Surface Multilayers at the Air–Water Interface from Sodium Polyethylene Glycol Monoalkyl Ether Sulfate/AlCl3 Solutions: The Role of the Size of the Polyethylene Oxide Group

Neutron reflectivity, NR, and surface tension, ST, have been used to study the surface adsorption properties at the air-water interface of the anionic surfactant sodium polyethylene glycol monododecyl ether sulfate (sodium lauryl ether sulfate, SLES) in the presence of Al(3+) multivalent counterions, by the addition of AlCl3. In the absence of AlCl3 and at low AlCl3 concentrations monolayer adsorption is observed. With increasing AlCl3 concentration, surface multilayer formation is observed, driven by SLES/Al(3+) complex formation. The onset of multilayer formation occurs initially as a single bilayer or a multilayer structure with a limited number of bilayers, N, ≤3, and ultimately at higher AlCl3 concentrations N is large, >20. The evolution in the surface structure is determined by the surfactant and AlCl3 concentrations, and the size of the polyethylene oxide group in the different SLES surfactants studied. From the NR data, approximate surface phase diagrams are constructed, and the evolution of the surface structure with surfactant and electrolyte concentration is shown to be dependent on the size of the polyethylene oxide group. As the polyethylene oxide group increases in size the multilayer formation requires increasingly higher surfactant and AlCl3 concentrations to promote the formation. This is attributed to the increased steric hindrance of the polyethylene oxide group disrupting SLES/Al(3+) complex formation.

Gas Chromatography/Electron Ionization Mass Spectrometric Analysis of Oligomeric Polyethylene Glycol Mono Alkyl Ethers

Polyethylene Glycol Monoalkyl Ethers, CxH2x+1 (OC2H4)n OH, (PEGMAE), are polar compounds like Polyethylene Glycols (PEG) and they undergo microbial degradation which produces toxic substances that are potentially dangerous to the environment. Therefore, the purpose of this study is to carry out proper identification and characterization of these compounds. The Electron Ionization (EI) and Chemical Ionization (CI) spectra of various PEGMAE were obtained by Gas Chromatography/Mass Spectrometry (GC/MS) and were used to identify and characterize these compounds. The characteristic cleavages in the EI and CI reactions of PEGMAEs were also studied. The results obtained showed that the methane CI mass spectra of the PEGMAE contain MH + ions and fragment ions similar to those found in their EI mass spectra. The relative abundances of the MH + ions are low, variable and increase with increasing sample size across the chromatographic peaks; but do not increase with increasing x or n. The base peaks of the low mass oligomers (x3) are PEG related (e.g., m/z 45, 59) but those of higher mass oligomers (x4) include the ion at m/z 63 (HOC2H4OH) H + or m/z 107 (HO (C2H4O)2 H) H + . There are no (MH-H2O) + ions or protonated dimer ions (n2, x2) in the spectra of PEGMAE. The Relative Molar Sensitivities (RMS) or the Relative Sensitivity per Gram (RSG) increases linearly with molecular polarizabilty or molecular weight with a non-zero intercept.

Phase equilibria in the water-alkali metal or ammonium sulfate-synthanol systems

Solubility was studied for the first time in ternary aqueous phase-separating systems containing synthanol DS-10 or ALM-10 (polyethylene glycol monoalkyl ethers based on primary fatty alcohols, CnH2n − 1O(C2H4O)mH, where m = 8–10 and n = 10–18 (synthanol DS-10) or 12–14 (synthanol ALM-10)) and inorganic salt (NH4)2SO4, Na2SO4, or Li2SO4 at 25°C. The boundaries of two-phase liquid equilibrium regions were determined. It was proposed to use the studied phase-separating systems for liquid extraction of metal ions.

Acceleration of phospholipid flip-flop in the erythrocyte membrane by detergents differing in polar head group and alkyl chain length

The detergents, alkyltrimethylammonium bromide, N-alkyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (zwittergent), alkane sulfonate, alkylsulfate, alkyl-β-d-glucopyranoside, alkyl-β-d-maltoside, dodecanoyl-N-methylglucamide, polyethylene glycol monoalkyl ether and Triton X-100, all produce a concentration-dependent acceleration of the slow passive transbilayer movement of NBD-labeled phosphatidylcholine in the human erythrocyte membrane. Above a threshold concentration, which was well below the CMC and characteristic for each detergent, the flip rate increases exponentially upon an increase of the detergent concentration in the medium. The detergent-induced flip correlates with reported membrane-expanding effects of the detergents at antihemolytic concentrations. From the dependence of the detergent concentration required for a defined flip acceleration on the estimated membrane volume, membrane/water partition coefficients for the detergents could be determined and effective detergent concentrations in the membrane calculated. The effective membrane concentrations are similar for most types of detergents but are 10-fold lower for octaethylene glycol monoalkyl ether and Triton X-100. The effectiveness of a given type of detergent is rather independent of its alkyl chain length. Since detergents do not reduce the high temperature dependence of the flip process the detergent-induced flip is proposed to be due to an enhanced probability of formation of transient hydrophobic structural defects in the membrane barrier which may result from perturbation of the interfacial region of the bilayer by inserted detergent molecules.

Physical characterization of non-ionic surfactant layers adsorbed at hydrophilic and hydrophobic solid surfaces by time-resolved ellipsometry

Non-ionic surfactant adsorption at hydrophobic and hydrophilic surfaces has been studied by time-resolved ellipsometry. Adsorption isotherms obtained for polyethylene glycol monoalkyl ethers (CnEm) at these surfaces are presented together with data on the adsorbed layer thickness and refractive index, giving information about the concomitant evolution of the molecular organisation within the adsorbed layers. It is shown that, whereas the surfactants are adsorbed as sub-monolayers or monolayers at hydrophobic surfaces, they form surface micelles or bilayer-type aggregates at hydrophilic silica. The adsorption/desorption kinetics of the surfactants at the different surfaces have also been investigated. A kinetic model based on the assumption of diffusive transport of surfactants through a stagnant layer, coupled with the idea of a local equilibrium existing between the adsorbed layer and the solution in its immediate vicinity, is used to interpret the experimental results. This was found to reproduce quantitatively the main features of the time dependence observed during adsorption and desorption at hydrophilic as well as hydrophobic silica.

Cyclophosphazenic Polypodands from Commercial Mixtures of Polyethylene Glycol Monoalkyl Ethers, "Brij": a Valid and Convenient Alternative to the Most Common Phase-Transfer Catalysts

The catalytic activity of cyclophosphazenic polypodand 3b, obtained as a crude mixture from the commercial Brij 30, was compared with that of the corresponding pure ligand in a number of solid-liquid (SL) and liquid-liquid (LL) phase-transfer reactions. The comparison was also extended to the commonly used catalysts 4-9 under the same conditions. The obtained results show that the crude mixture of 3b, due to its excellent cation-binding properties, has a catalytic efficiency higher than that exhibited by the other ligands. Furthermore its catalytic activity is comparable to that of the much more expensive 3b, in line with the very close complexation values found in both systems. For this reason the cheap and efficient crude mixture can be considered competitive with the most common phase-transfer catalysts, particularly under SL-PTC conditions

Interfacial behaviour of non-ionic surfactants at the silica-water interface revealed by ellipsometry

This work reports a new approach for in situ studies of thin adsorbed films (less than 100 Å) on layered substrates by null ellipsometry. The values of the absorbed film properties are obtained by first characterizing the substrate in different ambient media, having different refractive indices. These data are then used to apply the appropriate optical model for interpreting the adsorption data. We show that it is possible by this approach to make rather accurate and time-resolved measurements of the thickness and refractive index of thin adsorbed layers, in addition to the ordinary output data on the adsorbed amount. Besides the pure methodological part of the work, we also investigate the general features of the adsorption of polyethylene glycol monoalkyl ethers (CnEm) at the silica-water interface. The results featuring a series of surfactants with varying compositions confirm the cooperative nature of the adsorption process at the silica-water interface. This involves the formation of interfacial aggregates, with well-defined extensions normal to the surface, at a critical concentration.

Synthesis and catalytic activity of a new class of cyclophosphazenic polypodands

AbstractA new class of solid‐liquid phase‐transfer catalysts (SL‐PTC) has been prepared by the reaction of octachlo‐rocyclotetraphosphazatetraene and polyethylene glycol monoalkyl ether. These polypodands are found to be powerful metal cation complexing agents and very efficient catalysts in anion promoted reactions (e.g. nucleophilic substitution and reduction reactions).

Effect of Polyethylene Glycol Monoalkyl Ethers on Phase Transition Temperature of Dipalmitoylphosphatidylcholine Vesicle Membrane

Abstract The gel-to-liquid-crystalline phase transition temperature of a dipalmitoylphosphatidylcholine vesicle membrane was measured in the presence of polyethylene glycol monoalkyl ethers (CnEm) of various chain lengths of hydrophobic (n) and hydrophilic (m) groups. All of the surfactants, except of C12E1, depressed the transition temperature almost linearly with the concentration. The depression of the phase-transition temperature was analyzed by applying the van’t Hoff model for the freezing-point depression; also, the partition coefficients of the surfactants between bulk water and the membrane phase were estimated. Discussions were given concerning the dependence of the partition coefficients on the chain lengths of both oxyethylene and alkyl groups.

ChemInform Abstract: Synthesis of New Cyclophosphazenes Containing Polyoxyethylene Moieties.

AbstractReaction of hexachlorocyclophosphazene (I) with the polyethylene glycol mono alkyl ethers (II) yields the hexasubstituted derivatives (III).

Studies on the Synthesis and the Applications of Polyalkylene Glycol Derivatives. XII.

Tertiary ether amines were prepared and their surface active properties were discussed.The synthesis of the tertiary ether amines is as follows.* Halogenation of polyethylene glycol monoalkyl ether.* N-alkylation of monoethanol amine with the halogenated products.* Synthesis of the tertiary amines having three same chaines of alcoxy ethyl group.The surface active properties such as surface tension, foaming property, wetting power, dispersing power and emulsifying power, were measured and the influence of the number of moles of ethoxy group was discussed.The tertiary ether amines in the hydrochloric acid solution are good surfactants with very low foaming property and good wetting power.The values of surface tension increase with the increase in the number of the moles of ethoxy group, and on wetting power the values decrease.On dispersing power there exists an optimal number of moles of the ethoxy group.