Nonionic Pentaethylene Glycol Monododecyl Ether Research Articles

Impact of Adsorption Layer Properties on Drainage Behavior of Microscopic Foam Films: The Case of Cationic/Nonionic Surfactant Mixtures

Aqueous mixtures of cationic hexadecyltrimethylammonium chloride (CTAC) and nonionic pentaethyleneglycol monododecyl ether (C12E5) are investigated. Adsorption layer properties are systematically studied within a wide concentration range for a 1:1 molar ratio of the surfactants. Surface tension and dilatational rheology measurements are conducted by profile analysis tensiometry. The interfacial data are juxtaposed to drainage kinetics and stability results for microscopic foam films, investigated by microinterferometric thin liquid film instrumentation. The obtained results give experimental evidence of synergistic interactions in the studied solutions, as compared to the corresponding single surfactant systems. Specific runs of dynamic and equilibrium surface tension curves are registered against the total surfactant quantity; the surface dilatational elasticities for the mixtures are systematically higher. A clear correlation is established between adsorption layer performance and foam film characteristics. The maxima of the film lifetimes are well outlined, and the respective values are shifted towards lower overall concentrations. The reported results substantiate the key role of the adsorption layers, and the surface dilatational properties in particular, for foam film drainage kinetics and stability. The well-expressed synergy observed in adsorption layer and foam film properties suggests the substantial benefits of using mixed surfactant systems in the design and fine-tuning of foam systems for innovative applications.

Emulsified oil phase induced internal instability of ionic and nonionic foams revealed by coarse-grained molecular dynamics simulation

Oil phase has strong hydrophobicity and weak interface tension in the foam system, which will destroy the internal structure of foam and reduce the intrinsic stability of the foam film. Coarse-grained molecular simulation techniques were employed to investigate the effect of oil phases on the structural instabilities of two typical foam systems, i.e., ionic sodium dodecyl sulfate (SDS) and nonionic pentaethylene glycol monododecyl ether (C12E5). In both systems, the pseudo-emulsion film ruptures at a critical thickness, subsequently the oil phase enters the air-water interface subsequently. Instability mechanisms are obtained by analyzing dynamic processes of the foam systems. For the SDS foam system, an oil-bridge is formed in the foam film, which is attributed to the electrostatic repulsion between the SDS at the oil-water interface and that at the air-water interface, as well as the discontinuous distribution of SDS at the air-water interface caused by the structural reversal of SDS molecules. However, for the C12E5 foam system, oil phase spreads at the air-water interfaces, which is caused by the continuous distribution of the C12E5 molecules at the air-water interface and the attractive interaction between the neutral C12E5 molecules at the air-water interface and that at the oil-water interface. The outcomes of this work shed light on the destructive mechanism of foam films induced by oil phase and provide guidelines for the design of novel oil-resistant foam system.

Structural change of nonionic surfactant self-assembling at electrochemically controlled HOPG/electrolyte interface

In this study, we have observed structural change of self-assembling nonionic pentaethylene glycol monododecyl ether (C12E5) surfactant formed on a potential-controlled highly oriented pyrolytic graphite (HOPG) surface by electrochemical frequency modulation atomic force microscopy (EC-FM-AFM). At a negative and a positive potential side with respect to the point of zero charge (pzc), a periodic hemicylindrical structure is formed on the whole surface, while a disordered single-layered thin film is formed at a potential around the pzc. This demonstrates that the electrochemical tuning of the electrode potential enables precise control of the nonionic self-assembly structure. We also found that the self-assembly structure is expanded by Na+ ion contained in C12E5 solution. This can be reasonably explained by selective cation binding of a C12E5 molecule like a crown ether. In addition, we estimated a response time of phase transition between the two phases by electrochemical impedance measurement.

Evidence for a Critical Micelle Concentration of Surfactants in Hydrocarbon Solvents

The concentration-dependent aggregation of two surfactants, anionic sodium dioctylsulfosuccinate (Aerosol OT or AOT) and nonionic pentaethylene glycol monododecyl ether (C12E5), has been studied in cyclohexane-D12 using small-angle neutron scattering (SANS). A clear monomer-to-aggregate transition has been observed for both surfactants, spherical inverse micelles for AOT and hank-like micelles for C12E5. This suggests that a critical micelle concentration exists for surfactants of these kinds in nonpolar solvents. The nature of the transition is different for the two surfactants. AOT aggregates are the same size and shape with decreasing concentration until a sharp critical micelle concentration, after which they cannot be detected. However, C12E5 aggregates gradually decrease in size. These differences demonstrate that the strength of the solvophobic effect can influence the formation of surfactant aggregates in nonaqueous solvents.

Chemiluminescence of phthalhydrazide derivatives in organized media: Interactions with surfactants and cyclodextrins

The chemiluminescent oxidation of some phthalhydrazide derivatives, luminol (LUM), isoluminol (ISOL), N-(4-aminobutyl)-N-ethylisoluminol (ABEI) and N-(6-aminohexyl)-N-ethylisoluminol (AHEI), has been carried out in micellar media and in the presence of natural cyclodextrins (CDs), using Co(II) as catalyst and H2O2 as oxidant. The cationic cetyltrimethylammonium bromide (CTAB) and, in a lesser extent, the anionic sodium dodecyl sulfate (SDS) produce quenching in the chemiluminescence (CL) of all the luminophores at concentrations above the cmc, whereas slight enhancements are attained with the non-ionic pentaethylene glycol monododecyl ether (C12E5). On the contrary, the incorporation of the CDs to the reaction produces a remarkable intensification of the CL. Binding of the luminophores to the macrocycles and the micelles has been studied by Pulsed-Gradient-Spin-Echo-NMR (PGSE-NMR) and fluorescence anisotropy. The cationic CTAB decreases the emission mainly due to charge compensation as a result of the association of the luminophores and the luminescent intermediates to the micelles. The presence of the alkyl substituents of ABEI and AHEI provides an additional hydrophobic contribution to the binding process. SDS quenches this reaction as the micelles retain Co(II) on their anionic layer. The protection and stabilization of these luminophores or their luminescent intermediates provided by the cavities of the CDs make this family of cyclic oligosaccharides much more suitable agents than the surfactants for enhancing the CL in aqueous media for this specific reaction.

Solubilization of Polyelectrolytic Hairy-Rod Polyfluorene in Aqueous Solutions of Nonionic Surfactant

We report on the solubilization, phase behavior, and self-organized colloidal structure of a ternary water-polyfluorene-surfactant (amphiphile) system comprised of polyelectrolytic poly{1,4-phenylene[9,9-bis(4-phenoxybutylsulfonate)]fluorene-2,7-diyl} (PBS-PFP) in nonionic pentaethylene glycol monododecyl ether (C12E5) at 20 degrees C. We show in particular how a high amount (milligrams per milliliter) of polyfluorene can be solubilized by aqueous C12E5 via aggregate formation. The PBS-PFP and C12E5 concentrations of 0.31 x 10(-4)-5 x 10(-4) M and 2.5 x 10(-4)-75 x 10(-4) M, respectively, were used. Under the studied conditions, the photoluminescence (PL), surface tension, static contact angle, and (pi-A) isotherm measurements imply that D2O-PBS-PFP(C12E5)x realizes three phase regimes with an increasing molar ratio of surfactant over monomer unit (x). First, for x < or = 0.5, the mixture is cloudy. In this regime polymer is only partially dissolved. Second, for 1 < or = x < or = 2, the solution is homogeneous. In this regime polymer is dissolved down to the colloidal level. Small-angle neutron scattering (SANS) patterns indicate rigid elongated (polymer-surfactant) aggregates with a diameter of 30 A and mean length of approximately 900 A. The ratio between contour length and persistence length is less than 3. Third, for x > or = 4, the solution is homogeneous and there is cooperative binding between polymer and surfactant. Surface tension, contact angle, and surface pressure remain essentially constant with increasing x. A PL spectrum characteristic of single separated polyfluorene molecules is observed. SANS curves show an interference maximum at q approximately 0.015 A(-1), indicating an ordered phase. This ordering is suggested to be due to the electrostatic repulsion between polymer molecules adsorbed on or incorporated into the C12E5 aggregates (micelles). On dilution the distance between micelles increases via 3-dimensional packing. In this regime the polymer is potentially dissolved down to the molecular level. We show further that the aggregates (x = 2) form a floating layer at the air-water interface and can be transferred onto hydrophilic substrates.

Interactions between surfactants and {1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diyl}

The interaction between the water-soluble anionic conjugated copolymer poly{1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diyl} (PBS-PFP) and various surfactants has been studied in aqueous solution by UV–vis absorption spectra, fluorescence and electrical conductivity. It is suggested from the linear dependence of absorbance, fluorescence and electrical conductivity on concentration that in the absence of surfactant, moderately stable dispersions are formed. These are affected in different ways on adding cationic, anionic or neutral surfactants. With the cationic cetyltrimethylammonium bromide, quenching of fluorescence intensity and lifetime, and formation of a new emission occurs at concentrations well below the critical micelle concentration (cmc). Electrical conductivity measurements indicate a discontinuity at surfactant/polymer ratio corresponding to electroneutrality, due to complexation. With the anionic sodium dodecyl sulfate, fluorescence quenching is also observed, but is attributed to formation of some mixed polymer/surfactant aggregate. The most striking changes are observed with the non-ionic pentaethyleneglycol monododecyl ether (C 12E 5), where a blue shift in fluorescence emission, dramatic increases in lifetime and quantum yield, and changes in electrical around the cmc are interpreted in terms of incorporation of single polymer chains in elongated cylindrical micelles. This is supported by 1H NMR spectroscopic measurements.

Study of mixtures of n-dodecyl-beta-D-maltoside with anionic, cationic, and nonionic surfactant in aqueous solutions using surface tension and fluorescence techniques.

Surfactants of practical interest are invariably mixtures of different types. In this study, mixtures of sugar-based n-dodecyl-beta-D-maltoside with cationic dodecyltrimethylammonium bromide, anionic sodium dodecylsulfate, and nonionic pentaethyleneglycol monododecyl ether in solution, with and without supporting electrolyte, have been studied using surface tension and fluorescence spectroscopic techniques. Interaction parameters and mole fraction of components in mixed micelles were calculated using regular solution theory. The magnitude of interactions between n-dodecyl-beta-D-maltoside and other surfactants followed the order anionic/nonionic > cationic/nonionic > nonionic/nonionic mixtures. Since all surfactants have the same hydrophobic groups, strengths of interactions are attributed to the structures of hydrophilic headgroups. Electrolyte reduced synergism between n-dodecyl-beta-D-maltoside and ionic surfactant due to charge neutralization. Industrial sugar-based surfactant, dodecyl polyglucoside, yielded results similar to that with dodecyl maltoside, implying that tested commercial alkyl polyglucosides are similar to the pure laboratory samples in synergistic interactions with other surfactants. Fluorescence study not only supported the cmc results using tensiometry, but showed that interfaces of all the above mixed micelle/solution interfaces are mildly hydrophobic. Based on these results, an attempt is made to discover the nature of interactions to be a combination of intermolecular potential energies and free energy due to packing of surfactant molecules in micelles.

Unusual wetting dynamics of aqueous surfactant solutions on polymer surfaces

Static and dynamic contact angles of aqueous solutions of three surfactants—anionic sodium dodecyl sulfate (SDS), cationic dodecyltrimethylammonium bromide (DTAB), and nonionic pentaethylene glycol monododecyl ether (C 12E 5)—were measured in the pre- and micellar concentration ranges on polymer surfaces of different surface free energy. The influence of the degree of substrate hydrophobicity, concentration of the solution, and ionic/nonionic character of surfactant on the drop spreading was investigated. Evaporation losses due to relatively low humidity during measurements were taken into account as well. It was shown that, in contrast to the highly hydrophobic surfaces, contact angles for ionic surfactant solutions on the moderately hydrophobic surfaces strongly depend on time. As far as the nonionic surfactant is considered, it spreads well over all the hydrophobic polymer surfaces used. Moreover, the results obtained indicate that spreading (if it occurs) in the long-time regime is controlled not only by the diffusive transport of surfactant to the expanding liquid–vapor interface. Obviously, another process involving adsorption at the expanding solid–liquid interface (near the three-phase contact line), which goes more slowly than diffusion, has to be active.