Dioctadecyldimethylammonium Chloride Research Articles

Mechanism of high temperature induced destabilization of nonpolar organoclay suspension

HypothesisHigh temperatures can reduce the colloidal stability and rheological properties of nonpolar organoclay suspensions. The desorption of surfactants from organoclay has been proposed to explain this effect, but the mechanism remains unclear. In this work, it was hypothesized that the high-temperature-induced desorption of ion-exchanged surfactants is the main factor affecting the stabilization of suspensions. ExperimentsUsing the cationic surfactant dimethyldioctadecylammonium chloride (DODMAC) and Na-montmorillonite (Na-MMT), the high-temperature-induced reestablishment of the adsorption–desorption equilibrium of DODMAC in organoclay suspensions was studied. Thermogravimetric analysis combined with infrared spectroscopy and gas chromatography/mass spectrometry experiments were performed to determine the thermal decomposition products and, ultimately, infer the adsorption modes and locations of DODMAC on Na-MMT. Thermal analysis and rheology were utilized to demonstrate the high-temperature-induced desorption and transfer of DODMAC in organoclay suspensions. FindingsHigh temperatures induced the complete desorption of physically adsorbed DODMAC molecules from particle surfaces, the partial desorption of ion-exchanged dimethyldioctadecylammonium ions (DODMA+ ions) from particle surfaces, and the partial transfer of ion-exchanged DODMA+ ions from the surfaces to the interlayers. Importantly, desorption of ion-exchanged DODMA+ ions resulted in destabilization of the organoclay suspensions at high temperatures.

Extraction Coupled with Aerobic Oxidative Desulfurization of Model Diesel Using a B-type Anderson Polyoxometalate Catalyst in Ionic Liquids

An efficient aerobic oxidative desulfurization system was explored with polyoxometalate (DODMAC)3Co(OH)6Mo6O18·3H2O (DODMAC: Dimethyldioctadecylammonium Chloride) combined ionic liquids (ILs) as extraction solvent as well as reaction media for aerobic oxidative desulfurization of model diesel. N-octylpyridinium tetrafluoroborate ([Opy]BF4) was employed in the desulfurization system and the amazing recoverability showed without noticeable decrease in activity after seven cycles has aroused the great interest of us. Systematically investigations were carried out on the factors influencing the removal of DBT. The possible mechanism was also investigated hoping to provide new insights into diesel deep desulfurization processes.

When ternary PdCuP alloys meet ultrathin nanowires: Synergic boosting of catalytic performance in ethanol electrooxidation

Noble metal-phosphorus (NMP) alloys have received special attention in the electrocatalysis. Despite a few efforts, the fabrication of anisotropic multicomponent NMPs is largely unsuccessful. Here we develop a facile yet general surfactant-directed aqueous synthesis for one-dimensional (1D) ternary PdCuP alloy nanowires (NWs), and demonstrate their structural and compositional synergy in promoting catalytic performance towards ethanol electrooxidation. Anisotropic PdCuP NWs with an ultrathin diameter of 2.5 nm and ultralong length of hundreds of nanometers are synthesized via in-the-columnar epitaxial growth of crystalline alloys along columnar assemblies of amphiphilic dioctadecyldimethylammonium chloride (DODAC) by NaH2PO2 as the reducing agent and P source simultaneously. This protocol is also synthetically universal, enables the controllability in tuning the P contents and elemental compositions of multicomponent NMP NWs (for example, binary PdP, ternary PdAgP and PdPtP NWs). With synergistically structural and compositional merits, ultrathin PdCuP NWs display dramatically enhanced ethanol electrooxidation performance with a superior mass activity of 6.7 A mgPd−1, which is 9.4 fold higher than commercial Pd nanoparticle catalyst and also surpasses previously reported nanocatalysts. This approach will provide a new access for rational design of anisotropic non-metal-alloyed multicomponent noble metal-based nanocatalysts with desirable functions and synergies for a wide range of (electro)catalytic applications.

Ultrathin PdAg single-crystalline nanowires enhance ethanol oxidation electrocatalysis

Rational design and synthesis of highly efficient nanocatalysts towards electrochemical ethanol oxidation reaction (EOR) are of great importance for practical applications in direct ethanol fuel cells. Nanoengineering the nanostructures and compositions of EOR electrocatalysts has been of significnat interest because these paratmeters can enhance electrocatalytic kinetics and performance in the EOR. This article reports a synergistic EOR catalyst with remarkably enhanced electrochemical performance based on 3-nm-thick bimetallic PdAg single-crystalline nanowires. Kinetically stable yet thermodynamically unfavorable ultrathin PdAg single-crystalline nanowires (sNWs) are epitaxially grown in situ along nanoconfined hexagonal mesophases directly self-assembled by amphiphilic surfactants of dioctadecyldimethylammonium chloride under optimal synthetic condtions in aqueous solution. Due to the ultrathin and ultralong nanostructure, single-crystalline feature with a high density of low-coordinate atomic steps, high Pd utilization efficiency, and incorporation of more oxophilic Ag with Pd, PdAg sNWs show enhanced mass activity of 2.84 A mgPd−1 and stability (retained 43% after 2500 cycles) in the EOR. The kinetic studies reveal that significant enhancement in EOR performance can be ascribed to the synergic electronic and bifunctional effects of ultrathin PdAg sNWs.

Multimetallic Hollow Mesoporous Nanospheres with Synergistically Structural and Compositional Effects for Highly Efficient Ethanol Electrooxidation.

Controlling the nanostructures and chemical compositions of the electrochemical nanocatalysts has been recognized as two prominent means to kinetically promote the electrocatalytic performance. Herein, we report a general “dual”-template synthesis methodology for the formation of multimetallic hollow mesoporous nanospheres (HMSs) with an adjustable interior hollow cavity and cylindrically opened mesoporous shell as a highly efficient electrocatalyst for ethanol oxidation reaction. Three-dimensional trimetallic PdAgCu HMSs were synthesized via in situ coreduction of Pd, Ag, and Cu precursors on “dual”-template structural directing surfactant of dioctadecyldimethylammonium chloride in optimal synthesis conditions. Due to synergistic advantages on hollow mesoporous nanostructures and multimetallic compositions, the resultant PdAgCu HMSs exhibited significantly enhanced electrocatalytic performance toward ethanol oxidation reaction with a mass activity of 5.13 A mgPd–1 at a scan rate of 50 mV s–1 and operation stability (retained 1.09 A mgpd–1 after the electrocatalysis). The “dual”-template route will open a new avenue to rationally design multimetallic HMSs with controlled functions for broad applications.

Surface modification of La/SnO2–TiO2 nanocomposite via changing the ionic nature of surfactants

Surface of La/SnO2–TiO2 nanocomposite was modified during its synthesis using zwitterionic (3 (N-N dimethyloctadecyl ammonia) propane sulfonate), anionic (sodium dioctyl sulfosuccinate) and cationic (dimethyl dioctadecyl ammonium chloride) surfactants by sol gel method followed by reflux method. Effect of surfactants on morphology was investigated with scanning electron microscopy. Crystallite size was determined by using XRD pattern with the help of Scherrer and Williamson Hall equations, while particle size was calculated through transmission electron microscopy. Optical properties as well as photocatalytic activity was investigated against degradation of methylene blue under sun light. It was found that doping of lanthanum enhanced the photocatalytic activity of SnO2–TiO2 nanoparticles. A direct relation between particle size and band gap was found while both have inverse relationship with degradation and lattice strain.

Ultrathin PdPt bimetallic nanowires with enhanced electrocatalytic performance for hydrogen evolution reaction

We report a general bottom-up synthetic methodology to epitaxially grow 3-nm-thick single-crystalline PdPt bimetallic nanowires using amphiphilic dioctadecyldimethylammonium chloride as the surfactant template. Mechanistic studies show that the existence of Pd element is critical in the synthesis of bimetallic PdPt nanowires with controllable atomic ratios. Due to synergistic effect of anisotropic single-crystalline ultrathin one-dimensional nanostructures and bimetallic elemental compositions, the resulting PdPt nanowires exhibit superior electrocatalytic activity and stability towards the hydrogen evolution reaction (HER). Among them, bimetallic Pd86Pt14 nanowires show the best HER activity with a small overpotential of only 0.8 mV in acidic media at a current density of 10 mA/cm2 (12.8 mV positive than that of commercial Pt nanoparticles), and excellent stability with only 4.6% loss in activity after current-time chronoamperometric responses for 26 h. This surfactant template-directing approach opens a general method for precise control of anisotropic nanostructures in diverse bimetallic nanomaterials for the high-performance electrocatalysts.

Elucidating the effect of additives on the alkyl chain packing of a double tail cationic surfactant

HypothesisSome low molecular weight additives can strongly influence the phase behavior of aqueous surfactant systems, and this offers an important handle to control the properties of surfactant solutions and thus to optimize the stability and performance of various formulations. ExperimentsThe surfactant dioctadecyldimethylammonium chloride (DODAC) self-assembles into two lamellar phases in water, the gel phase (Lβ) and the liquid crystalline phase (Lα). Here, we present approaches to tune the gel-to-liquid crystalline transition temperature (Tm) with the use of additives. The effects of urea, sodium butyrate and butyric acid on the packing behavior of DODAC were determined. The surfactant phases were characterized using polarized optical microscopy (POM), differential scanning calorimetry (DSC), and small/wide angle X-ray scattering (SWAXS). FindingsAll three additives - urea, sodium butyrate and butyric acid yield a single and stable lamellar phase. Urea and sodium butyrate have only minor effects on Tm, butyric acid gives a large decrease as it stabilizes the Lα phase with respect to the Lβ phase. From the bilayer thickness of the gel phase an interdigitated or tilted packing of the surfactant molecules is suggested. The addition of sodium butyrate gives a highly interdigitated gel structure and resulted in the transition from lamellar liquid crystal to an isotropic L3 phase.

Development of surfactant-coated alginate capsules containing Lactobacillus plantarum

A novel concept is proposed in which alginate capsules containing a model probiotic Lactobacillus plantarum strain are coated with different surfactants with the aim to enhance cell survival during passage initially through simulated gastric (SGF) and then intestinal (SIF) fluid. The surfactants investigated included the anionic sodium dodecyl sulphate (SDS) and ammonium lauryl sulphate (ALS), the cationic dimethyldioctadecylammonium chloride (DDAC), benzalkonium chloride (BZK) and hexadecyltrimethylammonium bromide (CTAB), and the zwitterionic lecithin. Coating the alginate capsules with CTAB, BZK, ALS and SDS resulted in worst survival (∼4–9 log CFU/g decrease) compared to uncoated capsules (∼3 log CFU/g decrease), after 1 h exposure to SGF and two hours in SIF, which was most likely associated with their gradual penetration inside the microcapsules, as shown by confocal microscopy, and their antimicrobial effects. Coating the alginate capsules with DDAC improved cell survival compared to uncoated capsules (∼1.2 CFU/g decrease), whereas coating with lecithin improved cell survival considerably, resulting in almost complete recovery of viable cells in SGF and SIF (∼0.3 log CFU/g decrease). Although the interaction between alginate and lecithin was relatively weak as demonstrated by turbidity and contact angle measurements, it is likely that the protection was associated with the fact that lecithin was able to penetrate into the capsule rapidly, an observation that was supported by the fact that lecithin enhanced the viability of free cells in SGF and SIF. Lecithin has significant potential of being used as a coating material for probiotic containing capsules.

Hydrolytic Dephosphorylation of p‐Nitrophenyl Diphenyl Phosphate by Alkyl Hydroxamate Ions

AbstractThe kinetics of the hydrolysis of p‐nitrophenyl diphenyl phosphate (PNPDPP) by hydroxamate ions (R'(CO)N(RO−) such as octanohydroxamate (OHA−) and decanohydroxamate (DHA−) was investigated in dioctadecyldimethylammonium chloride (DODAC) and didodecyldimethylammonium bromide (DDAB) vesicles. The physicochemical properties of these surfactants were studied by conductivity and fluorescence measurements at 300 K. The hydrolysis of PNPDPP was studied in a vesicular system by using hydroxamate ions (OHA− and DHA−) at 300 K. The different catalytic effects of hydroxamate ions for the hydrolysis of PNPDPP in the vesicles were determined. All reactions followed pseudofirst‐order kinetics. The reactivity of DHA− was found to be higher than that of OHA− in the vesicular system toward the cleavage of phosphate ester. Further, the binding constants (K) and free energy change (∆G) for the associations of PNPDPP with DODAC and DDAB vesicles were determined spectrophotometrically as well as from the Benesi–Hildebrand (B–H) plots. The pseudophase model was applied for the quantitative treatment of the kinetic data in the vesicle systems.

Redox Reactions of Cobalt (III) Complexes of α –Hydroxy Acids by Pyridinium Bromo Chromate in the presence of Surfactants

The Kinetics of one electron transfer route seems to be un available for Pyridinium bromo chromate with cobalt (III) bound and unbound complexes of α –hydroxy acids in micellar medium pyridinium bromo chromate oxidises cobalt (III) bound and unbound α –hydroxy acids. It rules out the synchronous C-C bond fission and electron transfer to Cobalt (III) centre. Oxidation of above complexes increases with increase of temperature with increase in micellar concentration. An increase in the rate is observed. The added dimethyl dioctadecyl ammonium chloride (DDAC) increases the rate of oxidation of a reaction much more than Ammonium lauryl sulphate (ALS). Similar trends observed in Lactato and Glycolato Cobalt (III) Complexes

Optimisation of surfactant decontamination and pre-treatment of waste chicken feathers by using response surface methodology

Commercially processed, untreated chicken feathers are biologically hazardous due to the presence of blood-borne pathogens. Prior to valorisation, it is crucial that they are decontaminated to remove the microbial contamination. The present study focuses on evaluating the best technologies to decontaminate and pre-treat chicken feathers in order to make them suitable for valorisation. Waste chicken feathers were washed with three surfactants (sodium dodecyl sulphate) dimethyl dioctadecyl ammonium chloride, and polyoxyethylene (40) stearate) using statistically designed experiments. Process conditions were optimised using response surface methodology with a Box-Behnken experimental design. The data were compared with decontamination using an autoclave. Under optimised conditions, the microbial counts of the decontaminated and pre-treated chicken feathers were significantly reduced making them safe for handling and use for valorisation applications.

Effect of modification extent of montmorillonite on the performance of starch nanocomposite films

The mechanism of the influence of organically modified montmorillonites (OMts) with different modification extents on starch/OMt nanocomposites was investigated. The nanostructures of OMts and their dispersion in starch films were analyzed using X‐ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. The modifier content in the OMts increased with an increase in the added amount and molecular weight of the modifiers. The highest d‐spacing of 3.71 nm was achieved for the OMt modified with 30% dioctadecyl dimethyl ammonium chloride (DDAC). Intercalated nanostructures were formed between starch and the OMts modified with DDAC, whereas exfoliated nanostructures were formed between starch and the OMts modified with octadecyltrimethyl ammonium chloride (OAC) and octadecyl dimethyl benzyl ammonium chloride (ODBAC). The films with the OMt modified with 50% DDAC exhibited the highest tensile strength of 6.22 MPa. The water vapor permeability (WVP) of the film with the OMt modified with 30% DDAC exhibited a minimum value of 1.63 × 10−10 g · m/m2 · s · Pa. The amount and types of the modifiers in the OMts significantly influenced the structure and properties of the starch/clay nanocomposites. For a given polymer, the modification extent of Mt should be optimized to achieve high‐performance nanocomposites.

An investigation of kinetic and physicochemical properties of vesicular surfactants with oximate and hydroxamate ions: Hydrolytic reactions of organophosphorus pesticides

Rate constants have been determined spectrophotometrically for the reaction of paraoxon, parathion and fenitrothion (OP pesticides) with oximate (Ox−) and hydroxamate (HA−) ions in aqueous and cationic vesicular media at 300K. All reactions followed the pseudo-first-order kinetics. The surface properties i.e. the critical vesicle concentration (cvc), maximum surface access (Γmax), surface pressure at the cvc (Πcvc) and minimum surface area per molecule (Amin) of vesicular surfactants dioctadecyldimethylammonium chloride (DODAC) and didodecyldimethylammonium bromide (DDAB) with Ox− and HA− ions have been evaluated by conductivity and surface tension measurements at 300K. The standard Gibbs free energy of vesicle formation (ΔG0v), Standard Gibbs free energy of adsorption (ΔG0ad), and standard Gibbs free energy of vesicle formation per alkyl chain (ΔG0v, tail) of cationic vesicular surfactants with Ox− and HA− ions have also been evaluated. SEM (Scanning Electron Microscope) and TEM (Transmission Electron Microscope) were used to investigate the morphological behavior and size of vesicular surfactants. We observed a well-defined contour of vesicular surfactants that are mostly spherical and globular shape. The effects of vesicular morphology and chemical reactivity have been discussed.

Effects of grinding montmorillonite and illite on their modification by dioctadecyl dimethyl ammonium chloride and adsorption of perchlorate

Montmorillonite (Mt) and illite (Ilt) were ground for different times under wet condition and sequentially subjected to organic modification by dioctadecyl dimethyl ammonium chloride (DDAC). The influence of the grinding time on the obtained products in terms of DDAC loading and ClO4− adsorption were evaluated. Multiple techniques were used to characterize the changes in structure and morphology before and after mechanical or organic modification. Compared with Ilt, Mt showed a stronger resistance to mechanical treatment due to its swelling property. Silicon nuclear magnetic resonance (29Si NMR) spectra and X-ray diffraction (XRD) patterns of samples ground for 30min indicate the disintegration of Ilt and exfoliation of Mt, resulting in increase of ClO4− uptake by 147% for OIlt and 13% for OMt. Three stages in the grinding Mt can be proposed, including the separation of large particles into small particles, exfoliation of small particles, and disintegration of exfoliated single layers. In contrast, two stages are involved in the grinding Ilt, which are the destruction/exfoliation of large particles and further disintegration of small exfoliated layers.

Fabrication of electrospun PVDF nanofibers with higher content of polar β phase and smaller diameter by adding a small amount of dioctadecyl dimethyl ammonium chloride

In this work, the effect of dioctadecyl dimethyl ammonium chloride (DDAC, a kind of alkyl ammonium salt) on polar β phase content and the diameter of electrospun PVDF nanofibers was investigated for the first time. Our experimental results show that the diameter of the electrospun PVDF nanofiber could be largely reduced and the content of polar β phase also become dominant immediately by just adding a little amount of DDAC. When the mass fraction of DDAC reached 4%, the content of polar β phase increased by about 39.1% compared with PVDF nanofibers without DDAC. Besides, the crystallinity of PVDF nanofibers also increased with the addition of DDAC. Based on the results, the possible mechanism of cooperative effect between electrospinning and DDAC on fiber diameter and formation of β phase in PVDF was discussed.

The yield stress of model waxy oil after incorporation of organic montmorillonite

To study the influence of organic montmorillonite (OMMT) on the yield stress of the model waxy oil (LMO) under dynamic cooling, OMMT was prepared through ion exchange of the sodium montmorillonite with dimethyldioctadecylammonium chloride (DOAC). The incorporation of OMMT lead to a great reduction of the yield stress, which could be explained by the inhibition effect of OMMT on the wax gelation. For 100ppm OMMT loading, the yield stress reduced by 74.1% at 36°C. The inhibition effect was realized through decreasing the wax crystallinity, reducing the crystal dimension and introducing the electrostatic repulsion between the crystal particles. The role of thermal history on the yield stress was also studied. Compared with the pure LMO, the OMMT-doped LMO showed different dependence level on the thermal history, but similar trend with that. High testing temperature and short holding time facilitated a lower yield stress. Due to the presence of different shear stress during cooling, the cooling rate showed a complicated effect on the yielding process.

Nanoformulations for dimethyl fumarate: Physicochemical characterization and in vitro/in vivo behavior

Dimethyl fumarate has been demonstrated useful in relapsing remitting multiple sclerosis treatment (Tecfidera®). Nevertheless, since Tecfidera® capsules induce flushing, gastro-intestinal events and other more serious drawbacks, in this investigation a nanoparticle based system to be administered by an alternative way is proposed. In particular this study describes the preparation and characterization of dimethyl fumarate-containing solid lipid nanoparticles (SLN). Namely SLN based on tristearin, tristearin SLN treated with polysorbate 80 and cationic SLN constituted of tristearin in mixture with dimethyldioctadecylammonium chloride were investigated. The effect of the presence of dimethyl fumarate, functionalization by polysorbate 80 and dimethyldioctadecylammonium chloride was studied on morphology and dimensional distribution of SLN, by photon correlation spectroscopy and cryogenic transmission electron microscopy. Dimethyl fumarate release from SLN, studied by Franz cell, evidenced a Fickian dissolutive type kinetic in the case of SLN treated by polysorbate 80. Moreover fluorescent SLN were produced and characterized in order to investigate their in vitro permeability and in vivo biodistribution in mice.An in vitro study of fluorescent SLN permeability performed through a model of mouse brain microvascular endothelial cells, indicated that cationic SLN displayed higher permeability values with respect to neutral SLN and SLN treated by polysorbate 80. Biodistribution of polysorbate 80 treated SLN was studied by fluorescent imaging after intraperitoneal or intranasal administration in mice. The in vivo images indicate that polysorbate 80 treated SLN were able to reach the brain, even if they prevalently accumulated in liver and spleen, especially by intraperitoneal route.

Tribological properties of a synthetic mica-organic intercalation compound used as a solid lubricant

Solid lubricants have long been widely used to enhance lubricity and to achieve a longer die life in the field of tribological applications. Molybdenum disulfide (MoS2) is the most desirable solid lubricant because of its low friction coefficient, good anti-seizure ability stemming from easy cleavage and excellent adhesion to the metal surface. Although MoS2 performs well, it has a disadvantage in that its black appearance significantly stains the working environment. Therefore, non-black solid lubricants are strongly desired. Herein, we investigated the properties of a clay-organic intercalation compound as a solid lubricant. It is well known that some types of layered clay minerals have a cation exchange capacity and are capable of being intercalated with an organic cation between the silicate layers. This reaction is based on the ion exchange of exchangeable inorganic ions (Na+, K+, etc.) in the layered clay minerals. In this study, we examined the properties of synthetic mica, whose silicate layers were intercalated with a cationic organic compound (dioctadecyl dimethyl ammonium chloride). We evaluated the lubrication performance of the mica using a newly devised upsetting-ironing type tribometer. X-ray diffraction (XRD) results show that the distance between the silicate layers of the intercalated synthetic mica increased to 36.6Å from 12.6Å for a non-intercalated one. Owing to the increase in the interlayer distance, the lubrication coating containing the synthetic mica-organic intercalation compound showed a much improved lubrication performance than that of the non-intercalated one. These findings indicate that the lubricity of the clay minerals is highly dependent on the friction between the different silicate layers, and that the cationic organic compound incorporated into the interlayers can improve the lubricity. This result means that the clay-organic intercalation compound is a promising solid lubricant as an alternative to MoS2.

High temperature stable W/O emulsions prepared with in-situ hydrophobically modified rodlike sepiolite

HypothesisHydrophobic modification can influence interparticle interaction, their interfacial adsorption, and stability of particle-stabilized emulsions. Emulsions stabilized by rodlike particles are more stable than those prepared with spherical particles even at low concentrations. Moreover, interfacial adsorption of particles will be tuned by controlling the modification. Thus, it is possible to prepare stable W/O emulsions with in-situ modified rodlike particles. ExperimentsRodlike sepiolite particles were in-situ modified in oil using dimethyldioctadecylammonium chloride (DODMAC). High salinity solution (water) in paraffin oil (W/O) emulsion was prepared with the modified particles. Stability of emulsions at room temperature and after aging at 160°C for 24h was studied. Mechanism of emulsion stability was explored by rheological measurements and confocal fluorescent microscopy. FindingsRemarkable stability against coalescence was found at high temperature. The enhanced stability is due to the high viscosity of continuous phase. Moreover, modification of sepiolite particles at high DOMDAC concentrations enhances particle adsorption at water-oil interfaces and network in continuous phase, which improve the stability against sedimentation and coalescence of the W/O emulsions.