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The authors investigate the structural and colloid properties of a collector represented by amine hydrochloride treated by ultrasound and included in sylvinite flotation. Using the viscosity–temperature dependences, the Gibbs free energy is calculated for amine hydrochloride with and without treatment by ultrasound. It is found that ultrasound-treated amine added in salt-fat solutions are more stable to coagulation. From the synchronous thermal analysis, IR spectroscopy and X-ray phase analysis, it is inferred that ultrasonic treatment of amine hydrochloride slightly increases crystallinity of amine. The research findings improve understanding of the ultrasound effect on the change in the structural and colloid properties of the collector, which are important to optimizing output, sustainability and efficiency of potassium chloride production by flotation. [ABSTRACT FROM AUTHOR]

A combined experimental and molecular dynamic simulation approach was used to examine the structure and interfacial properties of solute-saturated micelles. The properties of dodecylbenzenesulfonate (DBS) micelles were examined in dodecane and benzene hydrocarbon systems. Pyrene fluorescence was used to determine the aggregation number of surfactant monomers in the micelle systems. Molecular dynamic (MD) simulations using energy minimization applying the CHARMm force field with the TIP3P model for water. Comparison of the DBS/benzene and DBS/Dodecane micelles equilibrium structures via radial distribution function (RDF) and probability distribution function (PDF) analysis indicates that the area per head group for the DBS/Benzene micelle interface is significantly larger than that of the DBS/Dodecane at the interface. It was also determined that benzene molecules can move freely within the micelle while dodecane is strictly confined in the core of the micelle. The increased interfacial area per monomer caused by the insertion of benzene also reduces the effectiveness of the surfactant, which has implications for use in various environmental applications. However, the DBS/benzene micelle can solubilize many more hydrocarbon molecules in one micelle with less surfactant monomer (i.e., lower aggregation number) per micelle due to the increased available packing positions within the micelle. This, in turn, increases the efficiency of the surfactant in real-world applications which is consistent with previous laboratory results. Understanding the differing solubilization characteristics of surfactants against various classes of hydrocarbons in single solute systems is a necessary step to beginning to understand their solubilization properties in the mixed waste systems prevalent in most surfactant enhanced remediation (SEAR) strategies. [ABSTRACT FROM AUTHOR]

In this study, the viscosity and viscoelasticity of Gemini surfactant solutions with different molecular structures were measured, and the micelle structure formed by self-assembly in the solution was observed and measured using FESEM and DLS. The effect of the molecular structure of anionic Gemini surfactants on the rheological properties of the solution was studied systematically. The experimental results showed that the carboxylate Gemini surfactants with long hydrophobic carbon chains and a moderate spacer group have better rheological properties in aqueous solution. The carboxylate Gemini surfactant solution aggregated to form more densely, larger-sized micelle structures than the sulfonate Gemini surfactant, so its viscosity and viscoelasticity are greater. When the carbon number of the spacer group was the same (s = 2), as the carbon number of the hydrophobic chain increased (m = 14,16,18), the hydrodynamic diameter increased, the size of the micelle structures formed by self-assembly in the solution increased, the micelles aggregated more tightly, and the solution viscosity and viscoelasticity increased. When the carbon number of the hydrophobic chain was the same (m = 18), as the carbon number of the spacer group increased (s = 2,3,4), the hydrodynamic diameter first increased and then decreased, the micelle structures exhibited the phenomenon of aggregation first and then disintegration, and the solution viscosity and viscoelasticity also increased first and then later decreased. These phenomena indicated that the change of Gemini surfactant molecular structure would lead to the change of its micelle microstructure and eventually lead to the change of solution rheological properties. [ABSTRACT FROM AUTHOR]

Aqueous micellar solutions of sodium dodecyl sulphate were investigated using X-ray scattering technique by a model-independent approach and dynamic light scattering in the concentration range 0.008 – 0.1 M. The obtained results are discussed in the framework of the concept of polyamorphous transition between ensembles of water clusters of low and high density levels. Polyamorphous transition accompanies the formation of dual structures of contact and separated by water micelles with different rates of diffusion.

Although LiNi0.8Co0.15Al0.05O2 (NCA) has various merits such as a high discharge capacity of ~ 195 mAh g−1, improved stability, and low cost, intergranular cracks in the NCA structure can suppress the electronic/ionic motion in the cathode. Thus, in this study, to minimize crack portions in the NCA cathode, we synthesized dense NCA cathode materials using micelle structures controlled with pluronic acid (F127) and polyvinyl alcohol (PVA) as polymer templates and evaluated the electrochemical performance in LIBs using coin-type cells. We found that all the as-prepared samples showed the LiNiO2-based structures doped with Co and Al. With an increasing amount of PVA, the 1st particles can be more agglomerated during heating and thus increase the size of the 2nd particles. Consequently, a significantly dense NCA structure consisting of less cracked 2nd particles can be prepared in the presence of F127 and PVA. In particular, the NCA cathode prepared with an optimal ratio of F127 to PVA exhibited the best electrochemical properties, i.e., high capacity and superior cycle life. [ABSTRACT FROM AUTHOR]

Herein, we characterized the micelle structure and hydration behavior of oleic acid-based gemini surfactants by small-angle neutron scattering. A larger counterion size (Li+ < Na+ < K+ < Cs+) resulted in decreased aggregation number (Nagg) of micelles and increased number of water molecules incorporated within the micelle (Nwater). We suggested that the incorporated water molecules prevent the formation of lower positivecurvature aggregates such as hexagonal liquid crystals. [ABSTRACT FROM AUTHOR]

In order to optimize the thickening performance of clean fracturing fluid, a series of sulfonate Gemini surfactants (DSm-s-m) were synthesized and identified by FTIR, 1HNMR, and 13CNMR. The surface tension curve was obtained by testing the surface tension of the surfactant at different concentrations, and the viscosity of sulfonate Gemini surfactant solution was measured by rheometer and investigated through changing the molecular structure. The microstructures of the solution were studied by SEM. The experimental results indicated that the CMC of the surfactant decreased with increasing the length of the hydrophobic chain. Moreover, the viscosity of sulfonate Gemini surfactant changed with the carbon number (s or m) of spacer group and hydrophobic chain, and the DS18-3-18 had superior viscosity behavior. The viscosity of the DS18-3-18 solution decreased with the temperature increase but was still 13.25mPa·s at 90∘C. The microstructures of DS18-s-18 solution demonstrated that the micelles of the DS18-s-18 solution changed from spherical to layer like and finally to commixture of spherical/layer like with increasing the carbon number of spacer group (s=2,3,4), and the viscosity of the solution increased firstly and then decreased correspondingly. The number of sheet micelles and bulk density in DS18-3-18 solution decreased with the increase of temperature, causing the decrease of the viscosity in solution. However, the intact sheet micelles still existing in solution at 90∘C meant that the DS18-3-18 had prominent temperature-resistant viscosity behavior. These phenomena illustrated that changing the molecular structure of surfactants could cause changes in their microstructure and finally lead to a change in the viscosity of the solution. [ABSTRACT FROM AUTHOR]

We previously showed that Caco-2 cell absorption of β-carotene from taurocholic acid (TA)-based mixed micelles differed depending on the composition of the micelles. In this study, the shapes and sizes of TA-based mixed micelles, that is, mixed micelles of TA, 1-oleoyl-rac-glycerol (MG), oleic acid (OLA), and either 1-palmitoyl-sn-glycero-3-phosphocholine (MPPC; i.e., a lysophospholipid) or 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC; i.e., a phospholipid) (60:3:1:0.75-12) were determined by using small-angle X-ray scattering (SAXS). We found that increasing the ratio of MPPC in mixed micelles of TA, MG, OLA, and MPPC was responsible for the previously observed enhanced β-carotene absorption by Caco-2 cells and changed the micelle shape from core-shell spherical to core-shell ellipsoidal. In contrast, increasing the ratio of POPC in mixed micelles of TA, MG, OLA, and POPC was responsible for the suppressed β-carotene absorption by the cells, changed the micelle shape from core-shell spherical to core-shell ellipsoidal to core-shell cylindrical, and caused a rapid increase in micelle volume. These results will be useful for understanding the mechanisms that mediate β-carotene absorption by cells and for developing technologies to improve the intestinal absorption of lipophilic components of drugs and nutrients. [ABSTRACT FROM AUTHOR]

This work investigates the temperature-dependent micelle formation as well as the micellar structure of the saponin aescin. The critical micelle concentration ( c m c ) of aescin is determined from the concentration-dependent autofluorescence (AF) of aescin. Values between c m c aescin , AF (10 ∘ C) = 0.38 ± 0.09 mM and c m c aescin , AF (50 ∘ C) = 0.32 ± 0.13 mM were obtained. The significance of this method is verified by tensiometry measurements. The value determined from this method is within the experimental error identical with values obtained from autofluorescence ( c m c aescin , T ( WP ) (23 ∘ C) = 0.33 ± 0.02 mM). The structure of the aescin micelles was investigated by small-angle X-ray scattering (SAXS) at 10 and 40 ∘ C. At low temperature, the aescin micelles are rod-like, whereas at high temperature the structure is ellipsoidal. The radii of gyration were determined to ≈31 Å (rods) and ≈21 Å (ellipsoid). The rod-like shape of the aescin micelles at low temperature was confirmed by transmission electron microscopy (TEM). All investigations were performed at a constant pH of 7.4, because the acidic aescin has the ability to lower the pH value in aqueous solution.

Self-organization of Triton X-100 (TX-100) surfactants in aqueous dispersion leading to their signature self-assembly is reported based on experimentally determined static structure factor data obtained from small-angle neutron scattering (SANS) experiments. Surfactant gels were formed for dispersions having 40% ≤ [TX-100] ≤ 55% ( v/ v). An unexplored correlation peak was noticed at a specific wave vector q* whose value increased with surfactant concentration. The form factor data could be described by modeling the micelles as core-shell structures (hydrophobic core with a polar shell). The intermicellar interactions were modeled with hard sphere, sticky hard sphere, and hard sphere in square well potential designations. We used a lattice model based on random walk formalism to theoretically describe this self-assembly, and observed that the cluster size decreased with TX-100 concentration consistent with experimental data. The self-organization of TX-100 in aqueous medium is presented. [ABSTRACT FROM AUTHOR]

Micellization of the cationic surfactant cetyltrimethylammonium bromide (CTAB) in dilute aqueous solutions of sodium butyrate (Na-Bu), sodium benzoate (Na-Ben) and sodium salicylate (Na-Sal) at different concentrations, viz. 0.005, 0.01, and 0.05 mol·L, has been investigated. Conductivity, steady-state fluorescence, dynamic light scattering (DLS), atomic force microscopy (AFM), and H NMR techniques shed light on different aspects of micellization. Various micellization parameters such as critical micelle concentration ( cmc), degree of ionization of micelle ( α), and standard Gibbs energy of micellization ( $$ \Delta G_{\text{m}}^{\text{o}} $$ ) have been obtained from conductivity measurements. Steady-state fluorescence has provided useful information about the cmc, polarity of cybotactic region and aggregation number of micelles of CTAB using pyrene as fluorescent probe in various aqueous salt solutions. The data have been analyzed in terms of hydrophobicity/hydrophilicity and polarizability of the anions of the added electrolytes. The content and nature of organic anions governs the shape and size of the micelles as revealed by DLS and AFM measurements. In the dilute concentration regime of added electrolytes, contrary to most of the reported studies pertaining to very high concentration of added electrolyte, no worm like micelles forming a gel like structure have been observed. H NMR experiments provided information about the sites of interaction of anions of added electrolytes with the surfactant head group. Graphical abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The structure of cadmium sulfide (CdS) micelle in stable aqueous solution of ethylenediaminetetraacetic acid was determined by dynamic light scattering, small-angle X-ray scattering and neutron scattering. The micelle aggregate is a single CdS nanoparticle with an average size of about 3 nm, the nanoparticle organic shell and the solvation shell are about 1 nm and 5 nm thick, respectively. These parameters were confirmed by the scanning semi-contact atomic force microscopy and powder X-ray diffraction studies of dry micelle cores isolated by high-speed centrifugation. The CdS micelle was correctly described by a simple double-shell model and was found to possess the structure corresponding to CdS quantum dots. [ABSTRACT FROM AUTHOR]

Sodium dodecyl sulfate (SDS) surfactants form micelles when dissolved in water. These are formed of a hydrocarbon core and hydrophilic ionic surface. The small-angle neutron scattering (SANS) technique was used with deuterated water (D2O) in order to characterize the micelle structure. Micelles were found to be slightly compressed (oblate ellipsoids) and their sizes shrink with increasing temperature. Fits of SANS data to the Mean Spherical Approximation (MSA) model yielded a calculated micelle volume fraction which was lower than the SDS surfactant (sample mixing) volume fraction; this suggests that part of the SDS molecules do not participate in micelle formation and remain homogeneously mixed in the solvent. A set of material balance equations allowed the estimation of the SDS fraction in the micelles. This fraction was found to be high (close to one) except for samples around 1 % SDS fraction. The micelle aggregation number was found to decrease with increasing temperature and/or decreasing SDS fraction. [ABSTRACT FROM AUTHOR]

The susceptibility of total casein and the individual caseins in reconstituted skim milk to transglutaminase (TGase)-induced cross-linking was studied as a function of incubation temperature (5–40 °C), pH (5·0–7·0) and mineral addition. Within the ranges studied, the level of total casein cross-linked increased with increasing temperature, pH and concentration of added trisodium citrate, whereas adding calcium chloride had the opposite effect. These effects can be largely related to the effects of these parameters on TGase activity. In addition, the parameters were also found to influence the susceptibility of κ-casein, and to a lesser extent β-casein, to cross-linking, whereas the susceptibility of αs1-casein was not affected. The susceptibility of κ-casein to cross-linking increased with increasing temperature and calcium chloride addition, but decreased with increasing pH and citrate content, whereas the susceptibility of β-casein to TGase-induced cross-linking decreased with increasing temperature, but was not affected by other parameters. These findings highlight the fact that selection of environmental conditions during cross-linking can be applied to tailor the surface, and hence possibly colloidal stability, of casein micelles in TGase-treated milk. [ABSTRACT FROM PUBLISHER]

Abstract: Chemical penetration enhancers such as micelles can be formed from the solubilisation of the nonionic surfactants in the nanoemulsion system which may then provide an effective solution to the problems associated with drug delivery systems. The structural properties of micelles comprising 5, 20, and 30 molecules of the nonionic surfactant Tween80 were investigated by all-atom level molecular dynamics simulation in explicit water system. The micelles with higher aggregation numbers showed a prolate shape, with the surface being dominated by the polar hydrophilic moieties of surfactant molecules. The average radius of gyration was between 1.1-4.9nm while the effective radius, determined from the radius of gyration was between 1.4-3.2nm. The estimated structural properties of the micelles formed may give us a more detail insight in understanding the complexity of these classes of nonionic surfactants. [Copyright &y& Elsevier]

Abstract: The manner of interaction of the coat peptide of the Pf3 phage (Pf3 peptide) with lipid bilayers has been extensively studied. Presently, we designed a derivative of the Pf3 peptide, referred to as the DDRK peptide, and subjected it to trypsin digestion to understand its physicochemical properties. In the presence of Triton X-100 used for solubilization of the peptide, digestion of DDRK with trypsin caused specific cleavage at the lysine (Lys) residue in its N-terminal region but not at other Lys residues or at the arginine residue. As the N-terminal region of the DDRK peptide is relatively hydrophilic, but its remaining region is hydrophobic, this hydrophobic region of the peptide would be expected to be coated by Triton micelles. Thus, we propose that the presence of such micelles protected against cleavage there, leading to selective cleavage by trypsin of the DDRK peptide at its hydrophilic Lys residue in the N-terminal part of the molecule. However, such a protective effect on the DDRK peptide against trypsin digestion was not observed with octylglucoside. The observed results are important for better understanding of the manner of interaction between detergents and hydrophobic peptides. [Copyright &y& Elsevier]

Abstract: Micelle-encapsulated multi-walled carbon nanotubes (MWCNTs) with sodium dodecyl sulfate (SDS) were used as catalyst support to deposit platinum nanoparticles. High resolution transmission electron microscopy (HRTEM) images reveal the crystalline nature of Pt nanoparticles with a diameter of ∼4nm on the surface of MWCNTs. A single proton exchange membrane fuel cell (PEMFC) with total catalyst loading of 0.2mg Ptcm−2 (anode 0.1 and cathode 0.1mg Ptcm−2, respectively) has been evaluated at 80°C with H2 and O2 gases using Nafion-212 electrolyte. Pt/MWCNTs synthesized by using modified SDS-MWCNTs with high temperature treatment (250°C) showed a peak power density of 950mWcm−2. Accelerated durability evaluation was carried out by conducting 1500 potential cycles between 0.1 and 1.2V with 50mVs−1 scan rate, H2/N2 at 80°C. The membrane electrode assembly (MEA) with Pt/MWCNTs showed superior performance stability with a power density degradation of only ∼30% compared to commercial Pt/C (70%) after potential cycles. [ABSTRACT FROM AUTHOR]

In order to develop a special surfactant that is suitable for improving oil recovery in low permeability reservoirs, and simultaneously meet the requirements of effectively improving sweep efficiency, displacement efficiency and good injectability, a series of new Gemini surfactants (GAC-3m, m = 14, 16, 18) were synthesized and characterized by FTIR and 1HNMR. The surface activity, interfacial activity, thickening properties and viscoelasticity of GAC-3m solution were systematically studied. The mechanism of viscosity and elasticity enhancement were also discussed. The results showed that with increasing the carbon number of hydrophobic chain, the surface activity and interface activity of GAC-3m surfactant increased first and then decreased, the viscosity and elasticity gradually increased. The micelle microstructures changed from sheet to network-like, and the structural morphology was gradually complete and compact, which made the viscosity and elasticity of the GAC-3m surfactant solution increase. GAC-3m exhibit fascinating surface activity, interfacial activity and low values of CMC (<4.5 × 10−4 mol/L), which is conducive to the formation of micelle structure at low concentration. The 0.5% GAC-316 solution can substantially reduce the oil-water interfacial tension to ultralow values (10−3 mN/m), and also possess attractive viscosity (18.58 mPa s) and viscoelastic properties (tanδ = 0.5 < 1). In accordance with the experimental studies, the novel surfactants (GAC-3m) are a kind of low interfacial tension viscoelastic Gemini surfactant, promising in enhancing the recovery of low permeability reservoirs. The insights gained from this study contribute to enriching the theoretical research of the viscoelastic Gemini surfactant and promote the applications of low interfacial tension viscoelastic Gemini surfactant in the recovery of heterogeneous low permeability reservoirs fields. • A series of new carboxylate Gemini surfactants GAC-3m were synthesized and characterized by FTIR and 1HNMR. • The interfacial activity, thickening property, viscoelasticity and thickening mechanism of GAC-3m solution were studied. • GAC-3m exhibit fascinating surface activity and low CMC, which is conducive to forming micelle structure at low concentration. • GAC-316 can reduce the interfacial tension to ultralow values, and also possesses attractive viscosity and viscoelasticity. • GAC-3m possess favorable shear-thinning behavior which is desirable for improving mobility control during EOR processes. [ABSTRACT FROM AUTHOR]

Abstract: Pollution of soils and sediments by heavy metals is an environmental concern. Among the remedial techniques, soil washing is proving to be reliable. Biosurfactant rhamnolipid has shown its potential as a washing agent. In this research, small angle neutron scattering (SANS) was employed to investigate the size and morphology of rhamnolipid aggregates and micelle structure in the presence of heavy metals Cu, Zn, and Ni. The results indicate the importance of the pH of the system in the morphology of the aggregates in the rhamnolipid solution. Creation of a basic condition by addition of 1% NaOH led to the formation of large aggregates (>2000 Å) + micelles with while in the acidic environment with 1% NaCl, large polydisperse vesicles with a radius about 550–600 Å were formed. The size of the aggregates in both acidic and basic condition is fine enough to ease the flow of the rhamnolipid solution through the porous media with the pore sizes as small as 200 nm. [Copyright &y& Elsevier]

Abstract: The phase behavior in the brine/sodium N-dodecanoyl sarcosinate (Sar)/isopropyl N-dodecanoyl sarcosinate (SLIP) system has been investigated by means of phase study, static light scattering, and small-angle X-ray scattering. The liquid crystal phases, hexagonal (H1) and discontinuous cubic (I1), melt upon the addition of NaCl, which shows the similar effect to the increasing of temperature. The addition of SLIP to the brine/Sar solution at high Sar concentration induces the phase transition from H1 to I1 via the isotropic micellar solution (Wm2). The micellar structure in the Wm2 phase also changes from the wormlike to the globular micelle with SLIP concentration. Adding NaCl reduces the repulsive force between the Sar head groups and simultaneously the space of the solubilized SLIP in the palisade layer, leading SLIP to shift their location further into the micelle core. As a consequence, the hexagonal symmetry breaks into the micelle solution and the liquid crystal order is destabilized entropically. [Copyright &y& Elsevier]

Even during the secretory stage of amelogenesis, enamel crystals thicken as amelogenins (the major protein component) decrease. To explain this phenomenon, we propose a model for amelogenin structure and function based upon the hypothesis that amelogenin forms micelles. Solubility and hydrophobicity analyses suggest that all but the hydrophilic amelogenin C-terminal regions aggregate via hydrophobic bonds to form a micelle core. Amelogenin micelles may form super-assemblies via their C-termini (KTKREEVD), which contain complementary positive (KTKR) and negative (EEVD) elements. Disassembly of the micelles through controlled proteolysis provides space for crystal growth. Initial cleavage (by enamelysin) removes the surface-accessible amelogenin C-terminus, exposing the middle portion to cleavage (by EMSP1). As a result, the 13-kDa amelogenin, a rod-shaped domain based upon ultrafiltration and transmission electron microscopy studies, is released. This model explains how amelogenin is able to 'space' and support the ribbon-like crystals and continuously yield space as the crystals thicken, until they are sufficiently mature to support themselves. Abbreviations: dentino-enamel junction (DEJ), sodium dodecyl sulfate (SDS), polyacrylamide gel electro phoresis (PAGE), transmission electron microscope (TEM). [ABSTRACT FROM AUTHOR]

Abstract: Well-defined amphiphilic block copolymers, poly(ethylene glycol) methyl ether-b-poly(styrene) (mPEG-b-PS), in which the PS blocks had different molecular weights, were synthesized by atom transfer radical polymerization (ATRP). Through introduction of selective solvents for the blocks, crystalline and amorphous blocks were self-assembled into different micelle structures in solutions. Atomic force microscopy (AFM) was used to characterize the micelle structures. It was observed that spherical micelles were always formed, whereas lamellar aggregates appeared only in the PS-selective solvent when the molecular weight of the PS block in mPEG-b-PS was low. The crystallizable mPEG blocks were self-assembled into either the core or corona of the micelles formed. The effects of the self-assembled structures on the crystallization behavior of mPEG blocks were then investigated with differential scanning calorimeter (DSC). When the PS molecular weight was much larger than that of mPEG, the result showed that the crystallinity of the mPEG block was lower when mPEG blocks crystallized in the corona than that in the core of the micelles. In this case, when mPEG blocks crystallized in micelle coronae, the micelle core formed by insoluble PS blocks was very big, so mPEG chains had to distribute sparsely in the micelle coronae. It was hard for mPEG chains in one micelle or among different micelles to gather together to crystallize. However, when the PS molecular weight was lower than that of mPEG, the crystallinity of mPEG was higher when the mPEG chains crystallized in the micelle corona, as the core formed by insoluble PS was small and the mPEG chains in the corona were easy to aggregate and crystallize. [Copyright &y& Elsevier]

Abstract: n-Octyl-β-d-glucopyranoside (OG) is a non-ionic glycolipid, which is used widely in biotechnical and biochemical applications. All-atom molecular dynamics simulations from two different initial coordinates and velocities in explicit solvent have been performed to characterize the structural behaviour of an OG aggregate at equilibrium conditions. Geometric packing properties determined from the simulations and small angle neutron scattering experiment state that OG micelles are more likely to exist in a non-spherical shape, even at the concentration range near to the critical micelle concentration (0.025M). Despite few large deviations in the principal moment of inertia ratios, the average micelle shape calculated from both simulations is a prolate ellipsoid. The deviations at these time scales are presumably the temporary shape change of a micelle. However, the size of the micelle and the accessible surface areas were constant during the simulations with the micelle surface being rough and partially elongated. Radial distribution functions computed for the hydroxyl oxygen atoms of an OG show sharper peaks at a minimum van der Waals contact distance than the acetal oxygen, ring oxygen, and anomeric carbon atoms. This result indicates that these atoms are pointed outwards at the hydrophilic/hydrophobic interface, form hydrogen bonds with the water molecules, and thus hydrate the micelle surface effectively. [Copyright &y& Elsevier]

Abstract: Bile salts are surfactants in bile that facilitate digestion, adsorption and excretion of various compounds. They have planar hydrophobic and hydrophilic faces and therefore exhibit some unusual properties; including the shape and size of the micelles that they form. Molecular dynamics simulations of the spontaneous aggregation of six bile salts (cholate (CHD), glycocholate (GCH), taurocholate (TCH), glycochenodeoxycholate (GCD), glycodeoxycholate (GDX) and glycolithocholate (GLC)) were performed in an aqueous phase to gain insight into their micellar structure. The aggregates that formed spontaneously from a random distribution of molecules ranged in size from 8 to 17molecules. The structures are highly dynamic in nature and are on average oblate, but can vary from oblate, to spherical or prolate. Intermolecular hydrogen bonding within the micelles was found to be an important factor in determining the micelle size, structure and dynamics. The molecular arrangement within the micelles maximises the hydration of the hydrophilic chains and some favourable orientations for adjacent molecules were acquired. The dynamics of the micelles were investigated using the hydrogen-bond lifetime autocorrelation function correlation time, which exhibited a relationship with the degree of hydroxylation. Comparison of the proposed model to the three literature models showed some features of the disk shaped models of Cary and Small [M.C. Cary, D.M. Small, Arch. Intern. Med. 130 (1972) 506–527] and Kawamura et al. [H. Kawamura, Y. Murata, T. Yamaguchi, H. Igimi, M. Tanaka, G. Sugihara, J.P. Kratohvil, J. Phys. Chem. 93 (1989) 3321–3326], whereas the third, inverted helix model of Giglio et al. [E. Giglio, S. Loreti, N.V. Pavel, J. Phys. Chem. 92 (1988) 2858–2862] can be discounted. The proposed model is better than the existing models, which assumed a rigid and structured molecular arrangement. [Copyright &y& Elsevier]

The parameters of the reaction of para-substituted 2-aminomethylphenols with 4-nitrophenyl bis(chloromethyl)phosphinate in toluene catalyzed by reversed micelles of polyethylene glycol-600 monolaurate depend on the nucleophile structure. The efficiency of the catalytic action increases in the series of substitutes C9H19 i

Rheological properties of a drag-reducing surfactant were investigated with the intention to find out the influence of shear rate and the duration of shear straining on the Shear Induced Structure. The ability of the surfactant to restore the broken drag-reducing network after the decrease of shear stress is well known. This property of reversible change caused by high shear at different flow conditions was compared to a more intensive mechanical straining by means of ultrasound. Observations using electronmicroscope and spectrometer are also presented. [ABSTRACT FROM AUTHOR]

We present a general method of determining the structure and charge of globular ionic micelles, using neutron small-angle scattering. The micellar solutions may have any concentration within the micellar phase. The method is based in part on an analytic calculation of the interparticle correlations between monodisperse spherical micelles, and we discuss the theory in some detail to justify its application to polydisperse globular particles. Experimental results are presented for several cationic and anionic micellar systems. [ABSTRACT FROM AUTHOR]

Nuclear magnetic resonance is applied to investigate the relative positions and interactions between cationic and non-ionic carbohydrate-based surfactants in mixed micelles with D 2 O as the solvent. This is accomplished by using relaxation measurements [spin-lattice (T 1 ) and spin-spin (T 2 ) analysis] and nuclear Overhauser effect spectroscopy (NOESY). This study focuses on the interactions of n-octyl β-d-glucopyranoside (C8G1) and β-d-xylopyranoside (C8X1) with the cationic surfactant hexadecyltrimethylammonium bromide (C 16 TAB). Whereas the interactions between carbohydrate and cationic surfactants are thermodynamically favorable, the NOESY results suggest that both of the sugar head groups are located preferentially at the interior core of the mixed micelles, so that they are not directly exposed to the bulk solution. The more hydrophilic sugar headgroups of C8G1 have more mobility than sugar heads of C8X1 owing to increased hydration. Herein, an inverted carbohydrate configuration in mixed micelles is proposed for the first time and supported by fluorescence spectroscopy experiments. This inverted carbohydrate headgroup configuration would limit the use of these mixed surfactants when access to the carbohydrate headgroup is important, but may present new opportunities where the carbohydrate-rich core of the micelles can be exploited., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)