Polyoxyethylene-type Nonionic Surfactants Research Articles

Effect of Polyoxyethylene-Based Nonionic Surfactants on Chemical–Mechanical Polishing Performance of Monocrystalline Silicon Wafers

The use of surfactants is crucial in the chemical–mechanical polishing fluid system for silicon wafers. This paper examines the impact of the functional group structure of polyoxyethylene-based nonionic surfactants and the variation in the polyoxyethylene (EO) addition number on the polishing performance of monocrystalline silicon wafers, to achieve the appropriate material removal rate and surface quality. The results demonstrated that the straight-chain structure of fatty alcohol polyoxyethylene ether (AEO-9) exhibited superior performance in wafer polishing compared to octylphenol polyoxyethylene ether (OP-9) and isoprenol polyoxyethylene ether (TPEG) and polyethylene glycol (PEG). By varying the number of EO additions of AEO-type surfactants, this study demonstrated that the polishing performance of monocrystalline silicon wafers was affected by the number of EO additions. The best polishing effect was achieved when the number of EO additions was nine. The mechanism of the role of polyoxyethylene-type nonionic surfactants in silicon wafer polishing was derived through polishing experiments, the contact angle, abrasive particle size analysis, zeta potential measurement, XPS, and other means of characterization.

Stability and Structural Analysis Using Small-Angle Neutron Scattering for Foam of Homogeneous Polyoxyethylene-Type Nonionic Surfactants with Multibranched Chains.

Small-angle neutron scattering can provide insight into the microstructure of the surfactant-stabilized foam. In this study, small-angle neutron scattering in combination with other techniques was employed to determine the microstructure of the foams stabilized using novel homogeneous polyoxyethylene (EO) alkyl ether-type nonionic surfactants with multibranched double chains (bC7-bC9EO12). Similarly, homogeneous EO-type nonionic surfactants with linear double chains (C8-C8EO12) and a linear single chain (C18EO12) were used. bC7-bC9EO12 and C8-C8EO12 surfactants with branched hydrophobic chains or double chains increased the foam stability and suppressed the draining. Furthermore, they formed rod-like micelles, and C18EO12 formed spherical micelles in the bulk solution. The foam film containing the plateau border contained micelles identical with those found in the bulk solution. For bC7-bC9EO12 and C8-C8EO12, the average radius of the bubbles immediately after foaming was of the order of hundreds of μm. Finally, these radii grew to the order of thousands of μm. Thus, a significant correlation was observed between the micellar structure and the stability of these foams.

Layer structure of quaternary-ammonium-salt-type amphiphilic gemini and trimeric ionic liquids

The layered structures formed by quaternary-ammonium-salt-type amphiphilic ionic liquids, including monomeric, identical and nonidentical alkyl chain-containing gemini, and star- and linear-structured three alkyl chain-containing trimeric types, were investigated by wide-angle X-ray scattering. A polyoxyethylene-type nonionic surfactant (C12EO6) was added to these amphiphilic ionic liquids, and the resulting layered structures were also elucidated. The spacing of the layers of the amphiphilic gemini ionic liquids increased with increasing fixed alkyl chain length in the two alkyl chains and differed according to the degree of alkyl chain dissymmetry. Amphiphilic trimeric ionic liquids displayed smaller layer spacings in linear structures than star structures, suggesting that the alkyl chains in the latter are loosely packed in layers due to the flexible spacer radiating from a central tertiary amine. Conversely, the alkyl chains in the linear structures are orderly and densely packed due to their close proximity. The addition of C12EO6 to the amphiphilic gemini and trimeric ionic liquids led to more ordered layers formed by the hydrophobic moiety, whereby the order decreased with increasing C12EO6 concentration.

A Review on the Environmental Behavior of the Polyoxyethylene Type Nonionic Surfactants Adjuvants in Pesticides

A Review on the Environmental Behavior of the Polyoxyethylene Type Nonionic Surfactants Adjuvants in Pesticides

Preparation of Nonionic Vesicles Using the Supercritical Carbon Dioxide Reverse Phase Evaporation Method and Analysis of Their Solution Properties.

We have previously reported a new preparation method for liposomes using supercritical carbon dioxide (scCO2) as a solvent, referred to as the supercritical carbon dioxide reverse phase evaporation (scRPE) method. In our previous work, addition of ethanol to scCO2 as a co-solvent was needed, because lipid molecules had to be dissolved in scCO2 to form liposomes. In this new study, niosomes (nonionic surfactant vesicles) were prepared from various nonionic surfactants using the scRPE method. Among the nonionic surfactants tested were polyoxyethylene (6) stearylether (C18EO6), polyoxyethylene (5) phytosterolether (BPS-5), polyoxyethylene (6) sorbitan stearylester (TS-106V), and polyoxyethylene (4) sorbitan stearylester (Tween 61). All these surfactants have hydrophilic-lipophilic balance values (HLBs) around 9.5 to 9.9, and they can all form niosomes using the scRPE method even in the absence of ethanol. The high solubility of these surfactants in scCO2 was shown to be an important factor in yielding niosomes without ethanol addition. The niosomes prepared with the scRPE method had higher trapping efficiencies than those prepared using the conventional Bangham method, since the scRPE method gives a large number of unilamellar vesicles while the Bangham method gives multilamellar vesicles. Polyoxyethylene-type nonionic surfactants with HLB values from 9.5 to 9.9 were shown to be optimal for the preparation of niosomes with the scRPE method.

Study on the catalytic performance of laccase in the hydrophobic ionic liquid-based bicontinuous microemulsion stabilized by polyoxyethylene-type nonionic surfactants

To formulate a compatible green medium for the conversion of a hydrophobic substrate by a hydrophilic enzyme, we investigated the phase behavior of pseudo ternary hydrophobic ionic liquid (HIL)/buffer/polyoxyethylene-type nonionic surfactant (CnEm)/n-alcohol system and the effects of the components on the formulation of the HIL-based bicontinuous microemulsion. It is found that small head group of the surfactant, high concentration of n-alcohol (medium/long alkyl chain) and low cohesive energy density of the HIL result in low phase transition temperature. In the CnEm stabilized compatible bicontinuous microemulsion, the kinetics of laccase catalyzed oxidation of 2,6-dimethoxyphenol were also investigated. It is found that in addition to temperature, n-alcohol is the key parameter affecting the catalytic performance of laccase, and the optimum n-alcohol depends on the type of HIL as an oil phase. All the kinetic parameters, such as Km, kcat, kcat/Km, and Ea (apparent activation energy), indicate that the bicontinuous microemulsion consisting of [Omim]NTf2/buffer/CnEm/n-hexanol is a suitable medium for the laccase-catalyzed reaction. To the best of our knowledge, this is the first report on the formulation of HIL-based bicontinuous microemulsion for enzyme catalysis.

Surface Adsorption and Micelle Formation of Polyoxyethylene-type Nonionic Surfactants in Mixtures of Water and Hydrophilic Imidazolium-type Ionic Liquid.

The interfacial properties of polyoxyethylene alkyl ether-type nonionic surfactants (CnEm) were studied in a hydrophilic room-temperature ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4), in the presence of water. These properties were assessed using static surface tension, pyrene fluorescence, and dynamic light scattering measurements. The interfacial properties were strongly dependent on the solution composition. Increased water concentration lowered the critical micelle concentration (cmc). The cmc was also affected by the lengths of both the alkyl and polyoxyethylene chains, but a greater impact was observed for the alkyl chain length. These results indicate that micellization occurs as a result of solvophobic interaction between surfactant molecules in the water/bmimBF4 mixed solutions, similar to aqueous surfactant systems. The cloud point phenomenon was observed for CnEm with a relatively low hydrophilic-lipophilic balance (HLB) value, and the relationship between the cloud point and water/bmimBF4 composition exhibited a convex upward curve. Furthermore, the mixing of bmimBF4 with water increased the surfactant solubility for water-rich compositions, suggesting that bmimBF4 acts as a chaotropic salt.

Pressure-Induced Transition of Bilayers in a Nonionic Surfactant Solution.

Pressure effects on the bilayers of polyoxyethylene type nonionic surfactant in water have been investigated by means of small- and wide-angle X-ray scattering. It has been found that the Krafft transition from the micellar phase to the lamellar gel phase (Lβ) is induced by pressure. By further pressurizing, the lamellar structural parameters, such as the repeat distance d and Caillé parameter η, discontinuously decrease after taking a maximum. All the SAXS and WAXS results revealed that the Lβ phase is transformed into the higher-ordered lamellar crystal phase (Lc). On the basis of these observations, we have made the T-C and T-P phase diagrams.

Effect of Polyoxyethylene Type Nonionic Surfactant and Polar Lipophilic Oil on Solubilization of Mixed Surfactant Microemulsion Systems

In the present report, the water solubilization capacity of water-in-oil microemulsion systems comprising mixed surfactants, that is, anionic sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and nonionic(s) [viz., polyoxyethylene (2) stearyl ether (Brij-72), polyoxyethylene (10) stearyl ether (Brij-76), polyoxyethylene (20) stearyl ether (Brij-78), polyoxyethylene (2) oleyl ether (Brij-92), polyoxyethylene (10) oleyl ether (Brij-97), and polyoxyethylene (20) oleyl ether (Brij-98)] was investigated in polar lipophilic oils [viz., ethyl myristate (EM), isopropyl myristate (IPM), and isopropyl palmitate (IPP)] with varying mole fractions of nonionic surfactant (Xnonionic) at a fixed surfactant concentration and 303 K. A maximum (i.e., synergism) in water solubilization (ω0,max) was observed at an optimal value of mole fraction of nonionic surfactant (Xnonionic,max). The solubilization efficiency parameter (SP*water) and the free energy of dissolution (ΔG0s) were evaluated for these mixed systems. All of the physicochemical parameters for solubilization (viz., ω0,max, Xnonionic,max, and SP*water) were found to be dependent on both nonionic surfactants and oils. A minimum in ΔG0s was observed at corresponding Xnonionic,max, where a maximum in SP*water was evidenced. The IPP-based system was found to be most efficient, whereas the EM-based system was least efficient. An attempt was made to correlate the interdependence of physicochemical (ω0,max or SP*water) and thermodynamic (ΔG0s) parameters.

Microscopic Investigation on Morphologies of Bilayer Gel Structure in the Mixed Polyoxyethylene-Type Nonionic Surfactant Systems

We investigated morphologies of lamellar domains below the Krafft temperature in the mixed polyoxyethylene-type nonionic surfactant, a C(16)E(6)/C(16)E(7)/water system, by using optical microscopy, confocal microscopy, small/wide-angle X-ray scattering, and small-angle neutron scattering. We have found that the morphology discontinuously changes from network structures of lamellar domains to spherical vesicles with increasing mole fraction of C(16)E(7), via the coexistence region of vesicles and network structures of lamellar domains.

Interfacial composition, thermodynamic properties and structural parameters of water-in-oil microemulsions stabilized by 1-pentanol and mixed anionic + polyoxyethylene type nonionic surfactants

The interfacial composition \( \left( {n_a^i} \right) \), thermodynamic properties and structural parameters of the stable water/(SDS + Brij-58 or Brij-78)/1-pentanol/heptane (or decane or isopropyl myristate) have been evaluated under various physicochemical environments by the dilution method. The results showed \( n_a^i \) values increase with increasing water content (ω = [water]/[surfactant]) for all the systems, whereas reverse trend was observed for (SDS/Brij-58)/heptane-derived system. The spontaneity of the transfer process of 1-pentanol from bulk oil to the interface \( \left[ { - \Delta G_t^0} \right] \) decreases with increase in ω for all the systems. The effective binding between 1-pentanol and surfactant(s) at the interface follows the order: SDS/Brij-78/IPM < SDS/Brij-58/IPM < SDS/Brij-78/Hp(or, Dc) < SDS/Brij-58/Hp(or, Dc), which corroborates well with the degree of spontaneity of the transfer process. The Gibbs free energy change \( \left( {\Delta G_t^0} \right) \), standard enthalpy change \( \left( {\Delta H_t^0} \right) \) and standard entropy change \( \left( {\Delta S_t^0} \right) \) have been found to be dependent on ω, type of nonionic surfactant and its content (Xnonionic), oil and temperature, because of the interdependence of the partition equilibrium of Pn between bulk oil and the interface, and strong adsorption of both surfactants at the interface. Synergism in \( \Delta G_t^0 \) and \( \left[ {{{\left( { - \Delta C_P^0} \right)}_t}} \right] \) (standard specific heat change) is evidenced at equimolar composition of SDS and Brij-58 in both oils at all temperatures and advocates more favorable applications for the synthesis of nanoparticles and the modulation of enzyme activity. The radius of water pool (Rw) was very sensitive to the increment of water content and tuned up by the addition of Brijs, which followed the order with decreasing size: IPM < Dc < Hp.

Micelle formation of nonionic surfactants in a room temperature ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate: Surfactant chain length dependence of the critical micelle concentration

Micellization behavior was investigated for polyoxyethylene-type nonionic surfactants with varying chain length (C n E m ) in a room temperature ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF 4). Critical micelle concentration (cmc) was determined from the variation of 1H NMR chemical shift with the surfactant concentration. The logarithmic value of cmc decreased linearly with the number of carbon atoms in the surfactant hydrocarbon chain, similarly to the case observed in aqueous surfactant solutions. However, the slope of the straight line is much smaller in bmimBF 4 than in aqueous solution. Thermodynamic parameters for micelle formation estimated from the temperature dependence of cmc showed that the micellization in bmimBF 4 is an entropy-driven process around room temperature. This behavior is also similar to the case in aqueous solution. However, the magnitude of the entropic contribution to the overall micellization free energy in bmimBF 4 is much smaller compared with that in aqueous solution. These results suggest that the micellization in bmimBF 4 proceeds through a mechanism similar to the hydrophobic interaction in aqueous surfactant solutions, although the solvophobic effect in bmimBF 4 is much weaker than the hydrophobic effect.

Micellization of sodium dodecyl sulfate and polyoxyethylene dodecyl ethers in solution

The effect of polyoxyethylene type nonionic surfactants (C12E n n = 3, 4, 5, 6, 7 and 8) on the aqueous solution of sodium dodecyl sulfate (SDS) in absence and presence of NaCl was examined using small-angle neutron scattering (SANS), dynamic light scattering (DLS), and viscosity measurements. Upon addition of C12E n , micellar size of SDS was found to increase significantly, and such micellar elongation was further enhanced in the presence of NaCl. Micellar growth is most significant in presence of shorter moieties of C12E n (e.g., n = 3, 4) as compared to higher ethereal oxygen content. The results of structural investigations with SANS and DLS to confirm this assumption are reported. The cloud point of C12E n has increased upon addition of SDS and decrease with NaCl, and a typical behavior is observed when both SDS and NaCl were present.

Micelle formation of polyoxyethylene-type nonionic surfactants in bmimBF 4 studied by 1H NMR and dynamic light-scattering

Critical micelle concentrations (cmc) of polyoxyethylene (POE)-type nonionic surfactants in a room temperature ionic liquid, bmimBF 4, were determined from the 1H NMR chemical shift of the surfactant as a function of concentration at various temperatures. Thermodynamic parameters derived from the temperature dependence of the cmc revealed that the micelle formation process of the surfactants in bmimBF 4 is entropy-driven at low temperature, while it changes to enthalpy-driven at high temperature. Similarity of this behavior to the case of aqueous system suggests that the micellization of surfactant molecules in bmimBF 4 is caused by a solvophobic interaction between hydrocarbon tails of the surfactants, which is analogous to a hydrophobic interaction in aqueous system. Compared with aqueous system, the solvophobic effect in bmimBF 4 is much weaker. It was demonstrated that the enthalpy–entropy compensation relation holds for the micelle formation in bmimBF 4 as well as in aqueous system.

Stabilization of foams solely with polyoxyethylene-type nonionic surfactant

Long-term stability is desirable for many foam-based systems, but achieving it is rather difficult. We report how foams can be stabilized solely with nonionic surfactant of the polyoxyethylene dodecyl ether (C 12EO n ). Effects of concentration and EO chain length of surfactants namely C 12EO 3, C 12EO 5, C 12EO 7 and C 12EO 9 on foaming properties (foamability and foam stability) were considered. The liquid drainage profiles of foams prepared were determined by reading the volume of the liquid drained as a function of time. The microstructure and viscosities on these colloidal systems were studied using optical microscopy and viscosimeter in attempt to explore the stability mechanisms. The experimental results suggest that the foamability goes through a maximum at the concentration of 10 wt.%, respectively, except for C 12EO 7. The optimal concentration of C 12EO 7 displaying maximum foaming capacity is at 1 wt.%. The stability of foams increases with increment of surfactant concentration. Foams stabilized solely by C 12EO 3 and C 12EO 5 at the concentration of 30 wt.%, respectively, exhibit the presence of lamellar liquid crystal adsorbed at the air/liquid interface, and could maintain more than 20 h without occurrence of collapse. In the case of foams generated from C 12EO 7 and C 12EO 9 under same concentration, respectively, there is no any optical fine structure between two air bubbles and thus has a poor stability only for tens of minutes. It is concluded that the stability of foams stabilized solely by C 12EO n surface active agents is attributed to the presence of lamellar liquid crystalline phases located at the gas/liquid interface. The role of liquid crystal in stabilizing foams could be explained in several mechanisms including hydrodynamic drainage, the mechanical strength of the liquid film and the diffusion rate of entrapped gas. The drainage behavior from these foams was well fitted by the empirical equation V t = V max t n /( K n + t n ) and the mechanism of liquid drainage was also discussed.

Preparation of trioctylamine-impregnated polystyrene–divinylbenzene porous resins for the collection of precious metals from water

A water-insoluble extracting solvent, trioctylamine (TOA), was solubilized in the aqueous micellar solution of a polyoxyethylene-type nonionic surfactant, polyethyleneglycol (10)-mono-4-nonylphenyl ether (PONPE-10). By mixing the solution and a polystyrene–divinylbenzene porous resin (Amberlite XAD-4), TOA was successfully impregnated into the resin. Gold(III), platinum(II), and palladium(II) were well extracted from hydrochloric acid to the TOA-impregnated resins. The extents of the extraction of platinum(II) and palladium(II) increased with increasing the amount of TOA impregnated. The TOA-impregnated filter disk was also prepared by passing aqueous mixture of PONPE-10 and TOA through an Empore disk involving polystyrene–divinylbenzene. The disk was useful for concentrating precious metals in water prior to their graphite furnace atomic absorption spectrometric analysis.

Solid phase extraction of some precious metals from hydrochloric acid to polystyrene-divinylbenzene porous resin impregnated with polyoxyethylene-type nonionic surfactant

The solid phase extraction of gold(III), platinum(II), and palladium(II) to surfactant-impregnated polystyrene-divinylbenzene porous resin (XAD-4) was studied. The extracting media could be prepared just by mixing the resin in aqueous surfactant solutions. XAD-4 impregnated with a nonionic surfactant, polyethylene glycol monooleyl ether, was useful for extracting gold(III) from hydrochloric acid. The extractions of platinum(II) and palladium(II) were improved in the use of XAD-4 impregnated with a nitrogen-containing nonionic surfactant, polyethylene glycol stearyl amine. On the other hand, base metals such as copper(II), cobalt(II), nickel(II) and zinc(II), were hardly extracted.

Protein separation with surfactant-coated octadecylsilyl silica involving Cibacron blue 3GA-conjugated nonionic surfactant

A novel medium for protein separation, namely affinity admicelle, was prepared by mixing of octadecylsilyl (ODS) silica gels, a polyoxyethylene-type nonionic surfactant (Triton X-100), and a surfactant-conjugated substrate (affinity ligand) in an aqueous solution. The ligand was synthesized by mixing a triazine dye (Cibacron Blue 3GA, CB) and a polyethylene glycol monooleyl ether (C 18EO 7, C 18EO 10, or C 18EO 20) having different length of polyoxyethylene moiety in weakly alkaline solutions. The amount of Triton X-100 sorbed on 1 g of ODS silica was 0.2 mmol. Affinity ligands having highly hydrophobic oleyl group were predominantly sorbed on ODS silica. The losses of Triton X-100 and affinity ligand were within 0.3% and negligible by washing the admicelles were with a 25-fold volume of 1 mM Tris–HCl solution (pH 7.4). The coating ODS silica with Triton X-100 was effective to prevent the irreversible sorption of albumin (bovine, serum). An NADH-dependent enzyme, alcohol dehydrogenase (ADH, yeast), was successfully collected on the admicelles involving CB-conjugated ligands (CB-C 18EO 20). The maximum collection of ADH to 90 mg/ml of affinity admicelles was 68 ± 4%. However, CB-C 18EO 7 and CB-C 18EO 10 having shorter polyoxyethylene unit were not available, suggesting the requirement of the spacer moiety in the affinity ligand. The recovery and purification factor based on the ratio of activity (unit)/protein (mg) from Whatman DE52-treated yeast extract was 27% and 12, respectively.

Protein separation with surfactant-coated polystyrene involving Cibacron Blue 3GA-conjugated Triton X-100

Through mixing of porous polystyrene particles (Amberlite XAD-4), non-ionic surfactants, and surfactant-conjugated substrates (affinity ligand) in an aqueous solution led to the formation of a novel medium (affinity admicelle) for protein separation. The ligand (CB–Triton) was synthesized by mixing a triazine dye (Cibacron Blue 3GA (CB)) and a polyoxyethylene-type non-ionic surfactant (Triton X-100) in weakly alkaline solutions. Triton X-100 and CB–Triton were competitively sorbed onto XAD-4. Albumin (bovine serum), alcohol dehydrogenase (yeast), and lysozyme (chicken egg) having specific interaction to CB were collected onto the affinity admicelle. On the other hand, the collection of ovalubmin (chicken egg white), having no binding ability to CB, was negligibly small. Lysozyme in 100 μl of chicken egg white, diluted with 900 μl of 10 mM Tris–HCl (pH 7.4), was successfully collected on 18 mg of CB–Triton admicelles and, then, it was eluted with 1 ml of aqueous solution of 100 mM phosphate (pH 7.4). The recovery based on the activity for the lysis of micrococcus and the concentration factor were 60% and 40 ( n=3), respectively.

Effect of Nonionic Head Group Size on the Formation of Worm-Like Micelles in Mixed Nonionic/Cationic Surfactant Aqueous Systems

The phase behavior, microstructure and rheological properties of mixtures of polyoxyethylene type nonionic surfactants (C12EOn, n = 0–4) and alkyltrimethylammonium bromide cationic surfactants in water were investigated. Upon addition of C12EO3 to the aqueous cationic system at high surfactant concentration, both the interfacial curvature of aggregates and the effective cross-sectional area per surfactant molecule, aS, decrease, resulting in a hexagonal-lamellar liquid crystal phase transition. This effect becomes more pronounced as the alkyl chain-length of the cationic surfactant increases. At low surfactant concentration, addition of nonionic amphiphile to micellar solution above a particular concentration, C*, induces a rapid unidimensional micellar growth, and particularly in CTAB systems viscoelastic micellar solutions of entangled wormlike micelles are formed. With successive addition of the nonionic amphiphile ultimately a micellar to lamellar phase transformation occurs. Rheological measurements within the Wm-phase show that with decreasing EO chain-length, C* also decreases and viscosity increases more swiftly with increasing concentration of nonionic amphiphile, suggesting a rapid micellar growth. This is attributed to the decrease in aS, as predicted by a simple geometrical model.