A lattice-gas hamiltonian for micellar binary solutions

An explicit Ising-spin lattice Hamiltonian is proposed as a model for studying the phase diagrams of micellar binary solutions on the micellar length scale. Incorporating many essential features, it can be used to check the validity of a previously suggested scenario for nonuniversality at the consolute point.     

Micellization of cetyltrimethylammonium bromide in the presence of 9-anthryl alkanols

 Surface tension measure-ments in aqueous cetyltrimethyl ammonium bromide were performed in presence of various amounts of 9-(hydroxymethyl)anthracene (AM), 9-[1-(1-hydroxy)ethyl]anthracene (THAE), and 9-[1-(1-hydroxy-2,2,2-trifluoro)ethyl]anthracene (TFAE). Free energies ΔG ^⊖ _m and ΔG ^⊖ _i of micellization and of adsorption to the air–water interface, respectively, were determined as well as the corresponding enthalpies and entropies. ΔG ^o− _m of micellization increased in the presence of AM and THAE, but became more negative when TFAE was added. In contrast to AM and THAE, TFAE addition decreases ΔS ^⊖ _i. For this peculiarity of TFAE, its location and orientation in micellar solution was investigated by means of UV and ¹⁹F-NMR spectroscopy. Received: 26 March 1997 Accepted: 16 May 1997     

High-performance liquid chromatographic analysis of a linear alkylbenzenesulfonate and its environmental biodegradation metabolites

A simple and fast method is described for determining a linear alkylbezenesulfonat e (LAS) and its potential sulfonated and unsulfonated metabolites in natural waters. This method includes extraction of 60 ml of water with an octadecyl-bonded silica (C₁₈) mini-column and analysis of the extract by high-performance liquid chromatography. A reversed-phase column with a 0.008 M potassium phosphate buffer (pH 2.2)-acetonitrile gradient as the mobile phase provides the separation. A UV detector, set at 215 nm, is employed.     

Separate detection of homologous surfactants by means of solid-contact unmodified and modified with molecular sieves potentiometric sensors

To improve the selectivity of surfactant sensors, the surface of their membranes was modified with molecular sieves with predetermined pore sizes. Water-soluble anionic, cationic and non-ionic surfactants were used as pore generators in the molecular sieves and introduced into the source membrane at the stage of its formation. The modified sensors enable detection of alkylsulfates homologues and alkylpyridinium with different lengths of the hydrocarbon chain (C₁₀-C₁₈); homologous poly(oxyethylated nonylphenols) differing in the number of oxyethyl groups (m = 10-100).A novel approach to separate detection of surfactant homologues implies the usage of inselective sensors as a multisensor system. The software-supported multisensor approach allows information of both mixture composition and concentrations of separate components in multicomponent systems to be obtained with a certain accuracy. Inselective non-modified sensors with the highest cross-sensitivity were used to design multisensor systems like an “electronic tongue”.The cross-sensitivity parameters of both source and modified sensors were estimated and the possibility of their usage in multisensor systems like an “electronic tongue” for analysis of multicomponent solutions of homologous surfactant is shown. Analytical signals were processed by artificial neural networks.     

Complete quality analysis of commercial surface-active products by Fourier-transform near infrared spectroscopy

Using proper calibration data Fourier-transform near infrared spectroscopy is used for developing multivariate calibrations for different analytical determinations routinely used in the surfactants industry. Four products were studied: oleyl-cetyl alcohol polyethoxylated, cocamidopropyl betaine (CAPB), sodium lauryl sulfate (SLS) and nonylphenol polyethoxylated (NPEO). Calibrations for major as well as very low concentrated compounds were achieved and every model was validated through linearity, bias, accuracy and precision tests, showing good results and the viability of NIR spectroscopy as a full quality control method for this products. Duplicate and complete analysis on a single sample takes at most 3 min, requiring neither sample preparation nor the use of reagents. The analytical reference procedures involved in this work represent the typical ones used in the industry and the NIR method shows good results in the analysis of components with weight concentrations less than 1%.     

Porphyrin-Based Bola-Amphiphiles as Structure-Directing Agents for the Synthesis of Mesostructured Silica

Summary.  Amphiphilic porphyrins with a bola-type arrangement of trimethylammonium headgroups can be used to generate M41S-type silica mesostructures with a lamellar topology and alternating organic–inorganic layers. Within the organic layers, the porphyrin entities are aggregated as shown by UV-Vis spectroscopy. The use of a bola amphiphile as structure-directing agent extends the possibilities of surfactant-controlled assembly of inorganic structures. In addition, the direct functionalization of the organic part of organic–inorganic hybrid nanostructures is possible due to the combination of the amphiphilic function with that of a chromophore. Corresponding author. E-mail: peter.behrens@mbox.acb.uni-hannover.de Received February 22, 2002; accepted May 8, 2002     

Use of cholate derivatives with submicellar concentration for controlling selectivity of proteins in hydrophobic interaction chromatography

Hydrophobic interaction chromatography (HIC) of proteins using a phenyl column has been performed in the presence of various surfactants with micellar and submicellar concentration ranges. Most surfactants were effective for a decrease in the retention of proteins in both concentration ranges. However, the use of anionic cholate derivatives increased the retention of the proteins with high isoelectric point, such as lysozyme, cytochrome c, and trypsin, in submicellar concentration range, and then decreased it above the critical micellar concentration, while the retention of the other proteins was monotonously decreased. The results of frontal chromatographic analysis of the surfactant and capillary electrophoresis for the proteins in the presence of surfactant show that in the submicellar concentration range, cholate derivatives allowed to be adsorbed on the stationary phase, while they exhibited no interactions with the proteins. Thus, it appeared that the increase in the retention of basic proteins was due to the electrostatic attraction between the proteins and cholate-modified stationary phase. We have applied the unique property of cholate to the separation of ovalbumin and lysozyme in egg white sample using hydrophobic chromatography.     

Ternary complex formation in aqueous solution between a beta-cyclodextrin polymer, a cationic surfactant and DNA

Polyelectrolyte complexes have been elaborated by mixing in water neutral poly(beta-CD), a cationic surfactant (DTAC) and herring sperm DNA fragments. The driving forces for the poly(beta-CD)/DTAC/DNA association in aqueous solution are, on the one hand, reversible inclusion interactions between the CD cavities of poly(beta-CD) and the alkyl group of DTAC, leading to the formation of a polycation and, on the other hand, electrostatic interactions between the opposite charges of the cationic surfactant and anionic DNA. Viscometry and SANS have been used to prove the occurrence of such ternary complexes in dilute aqueous solutions.     

Method for Determination of the Kinetic Parameters in Electrolytes Containing Surface‐Active Substances,Accounting for the Influence of Electrode Potential on the Changes of the Free Electrode Surface

Based on the generally accepted concept of the influence exerted by the value of the electrode potential on the degree of coverage of the electrode surface with molecules of the adsorbed surface‐active substance (SAS), an equation has been derived in the present paper which meets the requirement of consistency in stability of the electrode surface and allows for calculating the kinetic parameters of an irreversible electrochemical process, such as they would have been if the value of the electrode potential did not influence the size of the free (uncoated) electrode surface. The method is based on the substantial difference between the rates of charging of the double electric layer and of establishing adsorption equilibrium on the electrode surface. In the general case of adsorption of organic molecules this difference is about 4 orders of magnitude, which gives grounds for the assumption that within the short time from the start of the galvanostatic pulse till the onset of a Faraday process the electrode surface remains unchanged, i.e., such as it has been at the equilibrium potential. The method is illustrated by processing of the experimental data for two SAS widely used in the industrial practice, which yield a sufficiently long transition time (τ>5 s) and at the same time change more or less the overpotential of the electrochemical process. The electric charge of the electrode changes its sign at that, which is an indication of the applicability of the method in the potential regions in which SAS are desorbed as well.     

Polystyrene nanorod formation in <Emphasis Type="Italic">C</Emphasis><Subscript>12</Subscript><Emphasis Type="Italic">E</Emphasis><Subscript>5</Subscript> hemimicelle thin film templates

This paper reports the synthesis and characterization of polystyrene nanorods in hemicylindrical hemimicelles of a nonionic polyoxyethylene surfactant, C ₁₂ E ₅, on graphite. The surface structure is characterized by atomic force microscopy (AFM), Fourier transform infrared spectroscopy, and contact angle goniometry. Uniformly aligned polystyrene nanorods are captured by AFM. The nanorod dimensions are studied as a function of the reaction time and styrene monomer concentration. The template synthesis using self-assembled surfactant surface aggregates promises to create functional and stable nanostructures for optoelectronics and surface engineering.