Behenyl Trimethyl Ammonium Chloride Research Articles

Single-Crystalline Mesoporous Palladium and Palladium-Copper Nanocubes for Highly Efficient Electrochemical CO 2 Reduction

Single-Crystalline Mesoporous Palladium and Palladium-Copper Nanocubes for Highly Efficient Electrochemical CO ₂ Reduction

Asymmetry and Rippling in Mixed Surfactant Bilayers from All-Atom and Coarse-Grained Simulations: Interdigitation and Per Chain Entropy

Understanding lateral organizations of self-assembled bilayers is crucial to gain a control on functionally relevant topologies. We study self-assembled bilayers composed of a surfactant, behenyl trimethyl ammonium chloride (BTMAC), a cosurfactant, stearyl alcohol (SA), at a ratio of 2:1 in the presence of water at 283 K employing subsequent all-atom (AA) and coarse-grained (CG) molecular dynamics simulations. Differences in initial configurations lead to the formation of bilayers at ripple or square phases or interdigitated gel phases of varying trans-leaflet asymmetry. The AA ripple and gel phases are reproduced well at the CG level using bonded potentials from Boltzmann inversion of AA canonical sampling and nonbonded potentials from MARTINI. Inhomogeneous populations of disordered chains with higher per chain configurational entropy and tilt result in rippling stabilized by periodic hydrophobic energy barrier and strong interdigitation. Order parameters of the asymmetric bilayers are sufficiently coupled to the per chain entropies at both levels of resolutions to serve as a reflector of the per chain configurational entropy inaccessible by experiments. Thus, trans-bilayer asymmetry may be a controlling parameter to induce rippling in a bilayer of industrial importance. This work will be useful for future investigation on domain-associated transport and signaling in biomembranes at a low temperature.

Cationic collector conformations on an oxide mineral interface: Roles of pH, ionic strength, and ion valence

The adsorption of collectors at the solid–liquid interface to impart and enhance a mineral’s hydrophobicity is essential to mineral froth flotation. During adsorption, collectors must conform on the mineral surface with their nonpolar tails facing the aqueous phase to enhance the mineral’s hydrophobicity. This conformation is subject to conditions prevailing in the aqueous phase, such as the pH and nature of ions present. Since this conformation can affect the degree of hydrophobicity, molecular-level understanding of this phenomenon also is beneficial to improve hydrophobicity via adsorption layer manipulation. In this study, the structural conformational changes of cationic collector behenyl trimethyl ammonium chloride on a silica surface were studied using an in situ quartz crystal microbalance with dissipation (QCM–D) coupled with contact angle measurements. Two electrolytes, NaCl and CaCl2, were used to investigate the effects of ionic strength (IS) and ion valence. The QCM–D data at different pHs, both with and without a background electrolyte, revealed complex changes in the collector conformations and structure of the adsorption layer. Two distinct adsorption characteristics were also observed depending on ion valence: the presence of NaCl led to a thin, rigid layer (low dissipation), while a thick, soft layer (high dissipation) formed in the presence of CaCl2. Meanwhile, the increase in the IS of NaCl resulted in a more rigid adsorbed layer on the silica at both pHs. For CaCl2, the adsorbed layer became softer and highly dissipated at pH 5.7, whereas it became less soft at pH 10. This inconsistency in the rigidity with IS in the presence of CaCl2 was likely due to the strong sorption of Ca(OH)+ at a high pH. Interestingly, the imparted hydrophobicity decreased as the IS increased, with a greater extent of reduction at a high pH regardless of ion type. Moreover, it had a strong relationship with the ratio of dissipation and frequency change, with a lower contact angle at a higher ratio due to greater imbibition of water molecules and/or hydrated cations. These findings have implications for silica flotation systems wherein Ca2+ and Na+ cations are present in appreciable amounts.

Influence of water concentrations on the phase transformation of a model surfactant/co-surfactant/water system

The influence of water concentrations on phase transformations of a surfactant/co-surfactant/water system is investigated by using all atom molecular dynamics simulations. At higher water concentrations, where surfactant (behenyl trimethyl ammonium chloride, BTMAC) to co-surfactant (stearyl alcohol, SA) ratio is fixed, BTMAC and SA self-assemble into spherical micelles, which transform into strongly interdigitated one dimensional rippled lamellar phases upon decreasing water concentrations. Fragmentation or fusions of spherical micelles of different sizes are evident from the radial distribution functions at different temperatures. However, at lower water concentrations rippled lamellar phase transforms into an LβI phase upon heating. Our simulations reveal that the concentrations of water can influence available space around the head groups which couple with critical thickness to accommodate the packing fraction required for respective phases. This directs towards obtaining a controlling factor to design desired phases important for industrial and medical applications in the future.

A structural and temporal study of the surfactants behenyltrimethylammonium methosulfate and behenyltrimethylammonium chloride adsorbed at air/water and air/glass interfaces using sum frequency generation spectroscopy

Molecular scale information about the structure of surfactants at interfaces underlies their application in consumer products. In this study the non-linear optical technique of Sum Frequency Generation (SFG) vibrational spectroscopy has been used to investigate the structure and temporal behaviour of two cationic surfactants used frequently in hair conditioners. SFG spectra of films of behenyltrimethylammonium methosulfate (BTMS) and behenyltrimethylammonium chloride (BTAC) were recorded at the air/water interface and on glass slides following Langmuir Blodgett (LB) deposition. The assignment of the BTMS and BTAC spectral features (resonances) to the CH stretching modes of the surfactants was consolidated by comparison with the SFG spectrum of deuterated cetyltrimethylammonium bromide (d-CTAB) and by recording spectra on D2O as well as on water. The CH resonances arise from the methylene and methyl groups of the tail and head-groups of the surfactants. A slow collapse mechanism was observed following film compression of both BTAC and BTMS. The change in molecular structure of the films undergoing this slow collapse was followed by recording sequential SFG spectra in the CH region, and by monitoring the SFG intensity at specific wavenumbers over time. Additionally, LB deposition onto glass was used to capture the state of the film during the slow collapse, and these SFG spectra showed close similarity to the corresponding spectra on water. Complementary Atomic Force Microscopy (AFM) was used to elucidate the layering of the compressed and relaxed films deposited onto mica by LB deposition.

Role of Chain Length and Type on the Adsorption Behavior of Cationic Surfactants and the Silica Floatability

In this study, we investigated the adsorption isotherms of cationic surfactants (i.e., distearyl dimethyl ammonium chloride (DDAC), behenyl trimethyl ammonium chloride (BTAC), and stearyl trimethyl ammonium chloride (STAC)) onto silica surface and the corresponding silica floatability according to chain type and length of cationic surfactants. The results for the adsorption isotherms of cationic surfactants showed that the adsorptive amounts increased with increasing surfactant concentration, but differences in the position of the adsorption isotherms existed between DDAC, BTAC, and STAC. Specifically, in the high range of initial surfactant concentrations (i.e., 10 ¹5 ­10 ¹3 M), the adsorptive amounts increased with increasing hydrocarbon chain length. In addition, in the presence of DDAC, the adsorptive amounts were much greater than those in the presence of BTAC and STAC. The results were attributed to the fact that the increase in the hydrocarbon chain group of surfactants decreased the Gibbs free energy of the system, resulting in a shift of hemimicelle concentration toward lower concentration. Meanwhile, in the low range of initial surfactant concentrations (i.e., 5 © 10¹7­5 © 10¹6M), the adsorptive amounts were comparable regardless of surfactant type, which was due to the fact that the interaction between the cationic surfactants and the silica surface was mainly governed by electrostatic attractive force. The results from silica flotation and hydrophobicity tests showed that silica floatability increased with increasing hydrocarbon chain group of surfactants (i.e., floatability was in the order of DDAC > BTAC > STAC) under the conditions where the adsorptive amounts of the surfactants were comparable and that floatability results were consistent with those for the hydrophobicity of silica surface. Overall, the findings from the present study suggested that the hydrocarbon chain length and type of cationic surfactants play a significant role in both the adsorption behavior of surfactants and the silica floatability. [doi:10.2320/matertrans.M2014088]

The syntheses of transparent thin layers and spherical particles of nanoporous silicas

Thin layers of silica-surfactant hybrids with the thickness of several tens of nm formed on flat substrate from basic aqueous methanol solution containing tetraethoxysilane, behenyltrimethylammonium chloride, and ammonia. From the same solution, micrometer sized spherical particles of silica-surfactant hybrids were obtained. Both film and spherical particles were transformed to nanoporous silicas by calcination in air. The synthetic variables have been examined to find following dominant experimental parameters; the pore size of nanoporous silica spherical particles can be controlled by the synthetic temperature and the thickness of the films was varied by the amount of base.

In vitro skin permeation of hinokitiol loaded in vesicles composed of behenyltrimethylammonium chloride and stearic acid

Introduction: Behenyltrimethylammonium chloride (BTAC) and stearic acid (SA) could be associated with each other through salt bridges, and the associated BTAC/SA could build bilayer vesicles with the aid of hinokitiol (HKL). Method: The vesicles were prepared by a precipitation method and used to enhance the skin permeation of HKL. Results: In case the molar ratio of BTAC/SA/HKL was 1/1/0, no vesicle was observed on transmission electron microscope photos. When the molar ratio of BTAC/SA/HKL was 1/1/0.4, vesicle was observed together with some agglomerates. When the content of HKL increased to the ratios of 1/1/0.8 and 1/1/1.2, vesicles were exclusively observed. In vitro fluxes for 18 hours through hairless mouse skin of HKL dissolved in alcoholic solutions were less than 1 mg/cm2/h. Whereas the fluxes of HKL encapsulated in the vesicles were about three times higher than that of HKL in the alcoholic solutions. Conclusion: The vesicles could be used for the hair growth promotion.

The Influence of Bilayer Composition on the Gel to Liquid Crystalline Transition

We report molecular dynamics simulations of bilayers using a united atom model with explicit solvent molecules. The bilayer consists of the single tail cationic surfactant behenyl trimethyl ammonium chloride (BTMAC) with stearyl alcohol (SA) as the cosurfactant. We study the gel to liquid crystalline transitions in the bilayer by varying the amount of water at fixed BTMAC to SA ratio as well as by varying the BTMAC to SA ratio at fixed water content. The bilayer is found to exist in the tilted, L(beta') phase at low temperatures, and for the compositions investigated in this study, the L(beta') to L(alpha) melting transition occurred in the temperature range 330-338 K. For the highest BTMAC to SA composition (2:3 molar ratio), a diffuse headgroup-water interface is observed at lower temperatures, and an increase in the d-spacing occurs prior to the melting transition. This pretransition swelling is accompanied by a sharpening in the water density variation across the headgroup region of the bilayer. Signatures of this swelling effect which can be observed in the alkane density distributions, area per headgroup, and membrane thickness are attributed to the hydrophobic effect. At a fixed bilayer composition, the transition temperature (>338 K) from the L(beta') to L(alpha) transition obtained for the high water content bilayer (80 wt %) is similar to that obtained with low water content (54.3 wt %), confirming that the melting transition at these water contents is dominated by chain melting.

Effect of polyols on the shear-induced structure and rheological properties of behenyl trimethyl ammonium chloride/1-octadecanol/water ternary systems

The effects of polyols on the rheological properties of ternary systems consisting of behenyl trimethyl ammonium chloride (C 22TAC), 1-octadecanol (C 18OH) and water are studied to improve the stability against shear forces. The basic ternary systems behave as solids due to the formation of lamella liquid crystals called α gel. The external shear to ternary systems cause the rupture of gel structures and the systems are converted from solid-like bodies to viscoelastic liquids. It is confirmed through differential scanning calorimetry and small angle X-ray scattering that the mechanism resulting in the rheological changes is the release of bound water in lamella liquid crystals without rupture of lipophilic layers. When the trivalent alcohol like glycerin is added, the quaternary systems show the plastic responses even after violent shear. The phase transition behavior implies that the glycerin molecules are hardly incorporated into the lamella layers of lipophilic groups, but remain in the water layers to increase in their strength. The C 22TAC/C 18OH/glycerin/water quaternary systems can form the strong gel with high stability against external shear.

After‐Rinsing Hair Growth Promotions of Hinokitiol‐Containing Vesicles and Emulsions

Two kinds of topical dosage forms of hinokitiol (HKL), namely vesicles and oil‐in‐water (O/W) emulsions, were prepared. Behenyl trimethylammonium chloride (BTMAC) and fatty acids were used as bilayer‐forming materials of the vesicles, and oils were employed as oil phases of the emulsions. The substantivity of HKL in the preparations was evaluated in vitro using hairless mouse skins. After applying the preparations onto the skin and rinsing it, the amount of HKL left on the skin was determined using high performance liquid chromatography (HPLC). It was higher when HKL was encapsulated in cationic vesicles rather than in nonionic vehicles, emulsions. An ionic interaction between the cationic vehicle and negatively charged skin is likely to account for the high substantivity. Among the emulsion preparations, an emulsion having octyl salicylate as oil phase exhibited the highest substantivity of HKL. This is probably because that the oil is a good solvent for HKL and it is skin‐retentive. In vivo hair growth‐promotion effect of each dosage form was investigated, where the sample application onto the clipped backs of female mice (C57BL6) and the subsequent rinsing of the backs were done once a day for 30 days. Only HKL in the cationic vesicles had hair growth promotion effect, possibly due to the significant substantivity.

Structure and Performance of Cationic Assembly Dispersed in Amphoteric Surfactants Solution as a Shampoo for Hair Damaged by Coloring

In recent years, hair coloring gains popularity as a trend of consumer's hair care. This coloring frequently damages hair. In response to this, a new shampoo-base was developed for repairing hair damaged by coloring. The new shampoo-base was prepared by dispersing cationic assembly in a solution of amphoteric surfactants. The mixture of behenyl trimethyl ammonium chloride (C22TAC) and behenyl alcohol (C22OH) was applied as the cationic assembly, which are dispersed in amido propyl betaine laurate (LPB) solution. LPB, which behaves as an amphoteric surfactant, was used as the wash-base. It was verified from the results on the measurements of DSC, calorimeter polarization, cryo-SEM and X-ray diffraction that the cationic assembly has a crystalline structure in the LPB solution. The new shampoo-base was highly efficient to change the color-damaged hair from hydrophilic to hydrophobic. The friction level of the hair washed with the new shampoo-base recovered to the same state as that of healthy hair. The exfoliation of cuticle was reduced after washing with the new shampoo-base.

Effects of dioctadecyl dimethyl ammonium chloride on the rheological behavior of behenyl trimethyl ammonium chloride/1-hexadecanol/water ternary system

The effects of dioctadecyl dimethyl ammonium chloride (DODAC) on the rheological properties of ternary systems consisting of behenyl trimethyl ammonium chloride (C 22TAC), 1-hexadecanol (C 16OH), and water are studied to improve the long-term stability and to establish the preparation method of cosmetic products. The basic ternary systems behave as solids at low stresses, due to the formation of lamella liquid crystals called α gel. The additions of DODAC to ternary systems cause the rupture of α gel structures and transformation to vesicles. The structures of molecular assemblies are confirmed through particle size distribution, differential scanning calorimetry, and freeze fracture electron microscopy. The vesicle structures formed in coexistence of single-chain surfactant and double-chain surfactant are highly stable. Because the quaternary systems are considered to be constructed by the mixtures of α gel and vesicles at the appropriate concentrations of DODAC, the rheology can be controlled by the structural balance between them.

Rheological properties and structures of cationic surfactants and fatty alcohol emulsions: effect of surfactant chain length and concentration

Rheological and optical properties of cetyltrimethylammonium chloride (CTAC)/fatty alcohol (FA), behenyltrimethylammonium chloride (BTAC)/FA and CTAC/FA/hydroxyethyl cellulose (HEC) emulsions have been studied with particular emphases on the effects of FA content, the difference in the chain length of the hydrophobic groups between CTAC and BTAC, and the addition of a water soluble polymer, HEC. The effects of the FA content are to accelerate the structure development during the aging period and to increase the storage modulus, the yield stress, and the zero-shear-rate viscosity in the three emulsion systems investigated. At a low FA content of 2% w/w, lamellar and vesicular aggregates and isolated multilamellar vesicles can be observed in the CTAC/FA and BTAC/FA emulsions, respectively. At a high FA content of 6% w/w or with an excess of FA present, networklike structures and sunflower-like structures form, respectively, instead, inducing a higher entanglement storage modulus and a higher yield stress relative to those emulsions with a low FA content. The effect of adding HEC to the CTAC/FA emulsion is to reduce the entanglement storage modulus and the yield stress, consistent with the optical observation that the presence of the polymer disrupts the formations of lamella and vesicular aggregates and network structures.