N-dodecyl Ether Research Articles

Interactions of Hydrophobically Modified Polyelectrolytes with Nonionic Surfactants

Interactions of surfactants with hydrophobically modified polyelectrolytes in aqueous solutions are important in several applications such as detergency, cosmetics, food, and paints. Complexes formed in these systems raise some fundamental questions about the polymer-surfactant interactions that control their behavior. In this work, the interactions of a nonionic surfactant, penta-ethyleneglycol mono n-dodecyl ether (C(12)EO(5)), with a hydrophobically modified anionic polymer, poly(maleic acid/octyl vinyl ether) (PMAOVE), in aqueous solutions were studied using surface tension, viscosity, electron paramagnetic resonance (EPR) spectroscopy, light scattering, and fluorescence spectroscopic techniques. When the nonionic surfactant C(12)EO(5) was added to aqueous solutions of the anionic polymer PMAOVE, it was incorporated into the hydrophobic nanodomains of PMAOVE far below the the critical micelle concentration (cmc) of the surfactant. Two inflection points were observed corresponding to the critical complexation concentration (formation of mixed micelles composed of C(12)EO(5) and the octyl chains of PMAOVE) and the saturation concentration (saturation of the polymer with C(12)EO(5) molecules). Above the saturation concentration, the coexistence of pure C(12)EO(5) micelles and mixed micelles of PMAOVE and C(12)EO(5) was observed. Such a coexistence of complexes has major implications in their performance in colloidal processes.

Calorimetric Study on the Temperature Dependence of the Formation of Mixed Ionic/Nonionic Micelles

The differential excess enthalpy of mixed micelle formation was measured at different temperatures by mixing nonionic hexa(ethylene glycol) mono n-dodecyl ether with anionic sodium dodecyl sulfate or cationic dodecylpyridinium chloride. The experimental data were obtained calorimetrically by titrating a concentrated surfactant solution into a micellar solution of nonionic surfactant. The composition and the size of the mixed nonionic/ionic micelles at different surfactant concentrations were also determined. Pronounced differences in both composition and excess enthalpy were found between the anionic and the cationic mixed system. For both systems, the excess enthalpies become more exothermic with increasing temperature, but for the anionic mixed system an additional exothermic contribution was found which was much less temperature dependent. Temperature dependence of the excess enthalpy was attributed to the effect of the ionic headgroup on the hydration of the ethylene oxide (EO) groups in the mixed corona. Ionic headgroups located in the ethylene oxide layer cause the dehydration of the EO chains resulting in an additional hydrophobic contribution to the enthalpy of mixing. A high affinity of sodium dodecyl sulfate for nonionic micelles and an extra exothermic and less temperature dependent contribution to the excess enthalpy found for the SDS-C(12)E(6) system might be attributed to specific interactions (hydrogen bonds) between the sulfate headgroup and the partly dehydrated EO chain.

Quantitative Effect of Nonionic Surfactant Partitioning on the Hydrophile−Lipophile Balance Temperature

Phase behaviors of water/nonionic surfactants/isooctane systems are determined experimentally in temperature-global surfactant concentration diagrams. The surfactants are monodistributed polyoxyethylene glycol n-dodecyl ether. They are used as model mixtures of two, three, or five compounds or as constituents of a commercial surfactant. It is found that the phase diagrams of these systems are bent gradually toward the highest temperatures as the global surfactant concentration decreases. Each phase diagram is well-characterized by the curve of the HLB (hydrophile-lipophile balance) temperature versus the global surfactant concentration. For any fixed global surfactant concentration, this temperature is the middle temperature of the three-phase region; it can be calculated from an additive rule of the HLB temperatures of the surfactants weighted by their mole fractions at the water/oil interface. These mole fractions are determined through the pseudophase model using surfactant partitioning. Calculations require the knowledge of the critical micelle concentration, the partition coefficient between water and oil, and the HLB temperature of each surfactant of the mixture. This treatment can be used to correctly predict the variation of the HLB temperatures of the surfactant mixtures studied versus the global surfactant concentration. Furthermore, these calculations show that the observed curvature of the phase diagrams at the lowest global concentrations is due to the most favorable partitioning toward the oil of the lowest ethoxylated surfactant molecules.

Partitioning of Small Amphiphiles at Surfactant Bilayer/Water Interfaces: An Avoided Level Crossing Muon Spin Resonance Study

The temperature-dependent variation of local environment and reorientation dynamics of the small amphiphile 2-phenylethanol in lamellar phase dispersions of the dichain cationic surfactants, 2,3-diheptadecyl ester ethoxypropyl-1,1,1-trimethylammonium chloride (DHTAC) and dioctadecyldimethylammonium chloride (DODMAC), and the nonionic surfactant, tetra(ethylene glycol) n-dodecyl ether (C12E4), have been determined using avoided level crossing muon spin resonance spectroscopy (ALC-muSR). For cosurfactant radicals the hydrophobic or hydrophilic character of the surrounding media can be determined from their magnetic resonance signatures. Comparison of the three different bilayer-forming surfactant systems shows that the ALC-muSR technique is able to distinguish both major and subtle differences in the partitioning of the cosurfactant radicals between the different systems.

Ostwald ripening and solubilization in alkane in water emulsions stabilized by different surfactants

The Ostwald ripening (OR) and the solubilization of alkanes in water emulsions stabilized by the anionic surfactant sodium dodecyl benzene sulfonate (SDBS) and the non-ionic surfactants hexaoxyethylene glycol n-dodecyl ether (C12E6) and polyoxyethylene (20) sorbitan monolaurate (Tween20) were investigated. For the emulsions stabilized by the anionic SDBS the mass transport in both OR and solubilization is molecular diffusion of the oil through the continuous phase and no contribution of a micellar mediated transport is observed. For the emulsions stabilized by the non-ionic surfactants three different situations occur. For emulsions prepared in one single step under the high shear conditions of a microfluidizer, the mass transport is also mainly molecular diffusion. For already prepared emulsions to which extra surfactant is added, there is, besides molecular diffusion, a small contribution by a micellar mediated mechanism. Finally, in the solubilization studies the mass transport is a fusion–fission mechanism rather than molecular diffusion.

On the oligomeric state of the red blood cell glucose transporter GLUT1

We stripped human red blood cell membranes of cytoskeleton proteins at pH 12 without reductant, partially solubilized the obtained vesicles by use of octaethylene glycol n-dodecyl ether and purified the glucose transporter GLUT1 by anion-exchange chromatography followed by sulfhydryl-affinity chromatography, which removed most of the nucleoside transporter (NT) and the lipids. Eighty percent of the sulfhydryl-bound GLUT1 could be eluted with sodium dodecyl sulfate (SDS) indicating that the bound protein was multimeric. Matrix-assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-ToF-MS) of the trypsinized major SDS-PAGE zone of the purified material identified GLUT1 but no other membrane protein. Transmembrane helices 1 and 8 were among the detected fragments. The reconstituted purified GLUT1 showed glucose transport activity, although only approximately 0.05 high-affinity cytochalasin B (CB) binding sites were present per GLUT1 monomer. The vesicles used as starting material for the purification showed 0.4 CB sites per GLUT1 monomer, similar to vesicles prepared in the presence of dithioerythritol. The data are consistent with the coexistence of monomeric GLUT1 with high-affinity CB-binding activity and preferentially solubilized multimeric GLUT1 with no CB-binding activity in the red blood cell membrane vesicles prepared without reductant.

Ostwald Ripening of Alkane in Water Emulsions Stabilized by Hexaethylene Glycol Dodecyl Ether

The Ostwald ripening and the solubilization of alkane in water emulsions stabilized by the nonionic surfactant hexaethylene glycol n-dodecyl ether (C12E6) were investigated. For emulsions prepared under high-shear conditions in a microfluidizer, the presence of micelles swollen by alkane hardly affects the ripening rate. For already formed emulsions to which extra surfactant solutions were added, the ripening rates increased slightly with increasing added surfactant concentration. The ratio of the highest to the lowest observed ripening rate is no more than a factor of 3. The main aging mechanism is the transport of alkane by molecular diffusion through the continuous phase. This mechanism is confirmed by the temperature dependence of the ripening rate. The solubilities and the solubilization rates of different alkanes in several surfactants were determined. The solubilization rates of different alkanes are approximately proportional to their solubilities in micellar surfactant solution and are dependent ...

Shear-induced structural transformation of pentaethylene glycol n-dodecyl ether and lithium perfluorooctane sulfonate mixed-surfactant lamellar solution

The viscoelastic behavior of the shear-induced structural transformation from the lamellar phase to multilamellar vesicles (MLVs) of a mixed-surfactant system was investigated. The transformation was divided into two processes on the basis of the strain dependence of the apparent viscosity. The first stage is a lamellar-to-intermediate structure transformation. It was found that a strain, not an applied shear rate, governed this process. The second stage is an intermediate-to-MLV phase transformation, which was not controlled by the strain. These structure developments were found in the shear-thickening viscosity regime. The MLV phase formed by applying shear flow exhibited shear-thinning viscosity behavior and reversible response to shear flow. The viscoelastic properties of the MLV phase were investigated by dynamic viscoelastic measurements. Under oscillating shear deformation, the amplitude dependence of the dynamic modulus indicated that the viscoelasticity of the MLV depended on the initial structure, such as the number of vesicle shells and the size of the MLV, which is governed by the preshear rate.

Analytical investigation of the self-desorption of the oligomers of mixtures of a polydisperse ethoxylated surfactant with sodium dodecylsulfate from a silica/water interface

The adsorption isotherms onto a hydrophilic silica of mixtures of sodium dodecylsulfate (SDS) and of all the oligomers of a polydisperse nonylethylene glycol n-dodecyl ether (C 12E 9) surfactant were determined using a high-performance liquid chromatography (HPLC) technique. Incorporation of the anionic surfactant to the negatively charged silica surface is favored by the adsorption of the nonionic surfactant. Comparison between the adsorption isotherms of mixtures of SDS with a monodisperse C 12E 9 and a polydisperse C 12E 9 shows that the adsorption of SDS at the silica/water interface is stronger with the latter material than with the former in a large surface coverage domain. The composition of the surface aggregates and the variation of the oligomer distribution in these aggregates were determined. The previously described phenomena called self-desorption which was observed for the global C 12E 9 and SDS surfactant mixtures was confirmed: increasing the total concentration at a fixed surfactant ratio induces at high concentration a desorption of the anionic surfactant and all of the less polar oligomers from the solid/water interface. An interpretation scheme is proposed which assumes that the interaction of SDS is larger with the less polar oligomers than with the polar ones. The self-desorption effect could then be considered as the consequence of the polydispersity of the nonionic surfactant and to the net repulsion interaction between SDS and the silica surface as the mole fraction of SDS in the surfactant mixture increases.

Temperature Dependence of the Surface Phase Behavior and Micelle Formation of Some Nonionic Surfactants

The surface phase behavior and micellar properties of two nonionic surfactants, namely, ethylene glycol mono n-dodecyl ether (EGDE) and ethylene glycol mono n-tetradecyl ether (EGTE), have been investigated at different temperatures. From the study of film balance and Brewster angle microscopy (BAM), it has been observed that both of the amphiphiles show a first-order phase transition indicating conspicuous cusp points in their respective adsorption isotherms. This is further confirmed by the observation of bright 2-D condensed domains at the solution surfaces just after the appearance of the cusp points in the adsorption isotherms. Each of the above amphiphiles has a definite temperature above which they cannot show any indicative feature of phase transition, even with solutions of concentration above the critical micelle concentration (CMC) of the amphiphiles. These temperatures are found to be 23 and 37 °C for EGDE and EGTE, respectively. The CMC values of the amphiphiles increase with increasing tempe...

The role of the surfactant head group in the emulsification process: Single surfactant systems

To clarify the effect of the surfactant head group on the emulsification process, dilute dodecane in water emulsions were prepared in a small flow-through cell with three surfactants which had the same hydrocarbon tail length but different head groups. The different surfactants types were (a) a nonionic, hexa(ethyleneglycol) mono n-dodecyl ether (C 12E 6), (b) an anionic, sodium dodecyl sulfate (SDS), and (c) a cationic, n-dodecyl pyridinium chloride (DPC), and the emulsions were prepared under the same conditions. From dynamic light scattering measurements, it was shown that the mean steady state droplet size of the emulsions (obtained after 20 min dispersion) could be related to the interfacial tension at concentrations in the region of the cmc. This result was in agreement with laminar and turbulent viscous flow theory. However, the particle size versus surface tension data for the different surfactant systems did not fall on a single line. This behavior suggested that the surfactant played a secondary role in defining the droplet size (in addition to reducing the interfacial tension) possibly through diffusion and relaxation, during deformation of the interface. In addition, it was found that the values of the equilibrium “surfactant packing densities” of the different surfactants at the oil/water interface were almost equal near the cmc, but the mean droplet size and the interfacial tension at the cmc decreased following the order DPC>SDS>C 12E 6.

Topological transition in aqueous nonionic micellar solutions.

We have studied the topological transition of the nonionic micelles of a penta-ethyleneglycol mono n-dodecyl ether (C12E5)/DL-alpha-phosphatidylcholine Dimyristoyl (DMPC) mixture in water by light scattering and viscosity measurements. The topological transition concentration decreases with an increase of the mixing ratio of DMPC to C12E5. The topological transition point is strongly affected by defect energies of the end cap (epsilon(1)) and a threefold junction (epsilon(3)) and is compared with a recent theoretical study. This experimental study shows the first clear evidence for the topological transition in a nonionic micellar system resulting from balancing the defect energies.

Cationic and Nonionic Surfactant Adsorption on Thiol Surfaces with Controlled Wettability

We have shown that thiolated surfaces work very well as model substrates in adsorption measurements using the quartz crystal microbalance-dissipation. Functionalized self-assembled monolayers were prepared from mixtures of hydrophobically, SH-C 1 6 , and hydrophilically, SH-C 1 6 OH, terminated thiols, which allowed the interfacial energy of the surfaces to be changed in a systematic way. The prepared thiol surfaces were used as substrates for adsorption of a cationic (DTAB, dodecyltrimethylammonium bromide) and a nonionic (C 1 2 EO 8 , octa(ethylene oxide) mono(n-dodecyl ether)) surfactant. When the fraction of methyl groups at the surfaces was increased, the adsorption for both DTAB and C 1 2 EO 8 was increased. In particular, there is a transition from a micellar surfactant layer to a surfactant monolayer at 25-50% surface coverage of SH-C 1 6 groups. In addition, the role of the counterion in the adsorbed surfactant layer for the charged surfactant is discussed in terms of contribution to the mass and viscoelastic response determined by the quartz crystal microbalance.

Dependence of Phase Behavior of Some Non-ionic Surfactants at the Air–Water Interface on Micellization in the Bulk

The temperature-dependent surface phase behavior of two sparingly soluble surfactants, namely, ethylene glycol n-dodecyl ether (EGDE) and ethylene glycol n-tetradecyl ether (EGTE), at the air–water interface was investigated by film balance and Brewster angle microscopy (BAM). A cusp point followed by a pronounced plateau region in the surface pressure–time (π– t) adsorption isotherms of the amphiphiles measured by film balance indicates the first-order phase transition. Bright two-dimensional condensed phase domains in a dark background are observed by BAM just after the phase transition. In both cases the critical surface pressure necessary for the phase transition increases with increasing temperature. The domains are found to be circular up to 5 and 27°C for EGDE and EGTE, respectively, above which they show a fingering pattern. Condensed domains are observed up to 23 and 37°C for EGDE and EGTE, respectively. The surface properties of the amphiphiles are found to be markedly affected by their tendency to aggregate in the bulk as micelles. The CMC values of both the amphiphiles show a maximum at a definite temperature, T max, that corresponds well to their respective maximum temperatures of domain formation. An increase in temperature beyond T max results in an increasing trend for the formation of micelles. Consequently the system suffers from a shortage of two-dimensional surface concentration of the molecules to attain the surface pressure necessary for phase transition. With increasing temperature, the enthalpy, Δ H m°, and entropy, Δ S m°, of micellization change from negative to positive in both cases. An enthalpy–entropy compensation effect is found to hold for both the amphiphiles over the entire temperature range. The thermodynamic quantities reveal that the increase in temperature is favorable for micellization when the temperature exceeds the corresponding T max of the amphiphiles.

Effects of Oxyethylene Chain Length and Temperature on Partitioning of Homogeneous Polyoxyethylene Nonionic Surfactants between Water and Isooctane

Partition coefficients of homogeneous poly(oxyethylene glycol n-dodecyl ether) C12H25(OCH2CH2)iOH (i = 2−9) between water and isooctane were determined from experimental measurements in the temperature range 20−40 °C. All surfactants were found to have partition coefficients lower than unity, which indicates that their hydrophobic character is more important than their hydrophilic one. An increase in ethylene oxide number from 2 to 9 induces an exponential increase of the partition coefficient of 3 orders of magnitude, while an increase of 20 °C in the temperature decreases its magnitude only 0.5 of an order of magnitude. The hydroxyl group contribution to the free energy of transfer of the surfactant molecules from water to isooctane was found to be more important than that of an ethylene oxide group. An increase in temperature leads to an important decrease in its contribution, while the ethylene oxide contribution remains practically constant. Contributions of the functional groups of the surfactant molecules to the free energy of partitioning are evaluated in order to build up a database to predict the partitioning of nonhomogeneous nonionic surfactants of the same family within the temperature range investigated.

Spin Probe Study on the Interaction of Chitosan-Derived Polymer Surfactants with Lipid Membrane

Chitosan-derived polymer surfactants, sulfated N-acyl-chitosan (S–Cn–Chitosan), were synthesized and compared with commonly used low-molecular-weight surfactants, sodium dodecyl sulfate (SDS), dodecyltrimethyl ammonium chloride (DTAC), and octaethyleneglycol mono n-dodecyl ether (BL8SY), in their interaction with a lipid membrane using a spin probe method. A suspension of dipalmitoylphosphatidyl-choline (DPPC) spin-labeled strongly (10%) with a spin probe, 1-palmitoyl-2-(12-doxyl) stearoyl-phosphatidylcholine, was mixed with the surfactant solutions. The dissolution time of the DPPC membrane was estimated from the peak height change vs time, which was caused by the decrease in spin–exchange interaction. The times were 2, 4, and 70 s for BL8SY, SDS, and DTAC and 1.2 and 8.8 h for S–C10–Chitosan and S–C14–Chitosan, respectively, showing that the dissolution of the lipid membrane with polymer surfactants was far slower than that with low-molecular-weight surfactants. In addition, the time depended on the length of the alkyl chains of the polymer surfactants. Simulations of the ESR spectra of the DPPC-surfactant systems containing small amounts of surfactants were carried out in order to examine how the membrane structure was changed by the incorporation of surfactant molecules. By this analysis, it was revealed that the rigidity of the membrane was decreased by the addition of low-molecular-weight surfactants in the order of DTAC>SDS>BL8SY, inverse to the order of dissolution times. S–Cn–Chitosan, in contrast, increased the rigidity of the membrane, suggesting that polymer surfactants adhered to the lipid membrane and tightly enfolded the riposome anchoring their alkyl chains.

Overproduction in yeast and rapid and efficient purification of the rabbit SERCA1a Ca 2+-ATPase

Large amounts of heterologous C-terminally his-tagged SERCA1a Ca 2+-ATPase were expressed in yeast using a galactose-regulated promoter and purified by Ni 2+ affinity chromatography followed by Reactive red chromatography. Optimizing the number of galactose inductions and increasing the amount of Gal4p transcription factor improved expression. Lowering the temperature from 28°C to 18°C during expression enhanced the recovery of solubilized and active Ca 2+-ATPase. In these conditions, a 4 l yeast culture produced 100 mg of Ca 2+-ATPase, 60 and 22 mg being pelleted with the heavy and light membrane fractions respectively, representing 7 and 1.7% of total proteins. The Ca 2+-ATPase expressed in light membranes was 100% solubilized with L-α-lysophosphatidylcholine (LPC), 50% with n-dodecyl β- D-maltoside (DM) and 25% with octaethylene glycol mono- n-dodecyl ether (C 12E 8). Compared to LPC, DM preserved specific activity of the solubilized Ca 2+-ATPase during the chromatographic steps. Starting from 1/6 (3.8 mg) of the total amount of Ca 2+-ATPase expressed in light membranes, 800 μg could be routinely purified to 50% purity by metal affinity chromatography and then 200 μg to 70% with Reactive red chromatography. The purified Ca 2+-ATPase displayed the same K m for calcium and ATP as the native enzyme but a reduced specific activity ranging from 4.5 to 7.3 μmol ATP hydrolyzed/min/mg Ca 2+-ATPase. It was stable and active for several days at 4°C or after removal of DM with Bio-beads and storage at −80°C.

Conformational Analysis of Nonionic Surfactants by FT-Raman Spectroscopy Measurements

A conformational analysis of ethylene oxide and methylene chains for the mixtures of nonionic surfactant (polyethyleneglycol mono n-dodecyl ether, C12EOn = 5 ∼ 8) with pure water was carried out by FT-Raman spectroscopy measurements to clarify the relationship between the conformation of the methylene or ethylene oxide chain and the aggregate for C12EOn in the pure water. The trans conformation for C-C bond in the hydrophilic ethylene oxide chain in liquid crystalline phase was less than that in aqueous micellar solution and pure C12EOn. On the other hand, the order of the hydrophobic methylene chain decreased with increasing concentration of C12EOn.

Self-Desorption of Mixtures of Anionic and Nonionic Surfactants from a Silica/Water Interface

The adsorption of a mixture of two surfactants, the anionic sodium dodecyl sulfate and the nonionic nonylethylene glycol n-dodecyl ether, from water to a hydrophilic silica dispersion has been studied at pH = 5.0 and 25 °C in a large concentration range at several surfactant compositions by a classical depletion method. The adsorption of the latter compound onto silica induces the incorporation of the former by the formation of mixed surfactant aggregates. However, at high total surfactant concentration, about 100 times the mixed critical micelle concentration, both surfactants are partially desorbed from the silica surface. This behavior is qualitatively interpreted as the consequence of two phenomena: on one hand, the strong interaction between the anionic and the nonionic surfactant in the bulk above the critical micelle concentration and on the other hand the repulsion which occurs between the negatively charged dissociated silanol groups and the anionic surfactant in the mixed aggregates at the silica/water interface. At high total surfactant concentration and above a specific anionic/nonionic surfactant ratio the former phenomenon is favored over the latter, hence the desorption of both surfactants.

Thermodynamic Study of Phase Transitions in Lyotropic Liquid Crystals: Adiabatic Calorimetry on Nonionic Surfactant C12E6−Water System

The heat capacities of the binary system consisting of a nonionic surfactant, hexaoxyethylene n-dodecyl ether (C12E6), and water were precisely measured as a function of temperature by adiabatic calorimetry over the temperature and the concentration ranges where lyotropic liquid crystals are formed. The enthalpy and entropy of transitions were determined for all transitions observed. The enthalpy and entropy of transition between liquid crystalline phases suggest that the liquid crystalline phases in this system are mainly constructed by C12E6 molecules with a fixed amount of water. The excess heat capacities, as estimated by measuring the heat capacity of neat C12E6, are positive over the entire temperature and concentration ranges. The excess heat capacities also support the suggestion given above concerning the role of C12E6 molecules on the structure building.