Alkyldimethylamine Oxide Research Articles

ИССЛЕДОВАНИЕ АДСОРБЦИИ АМФОТЕРНОГО ПАВ АМИНОКСИДА НА МИКРОБНЫХ КЛЕТКАХ С ЦЕЛЬЮ ВЫДЕЛЕНИЯ ВЕЩЕСТВ БЕЛКОВОЙ ПРИРОДЫ

A promising direction in obtaining effective forages is the creation of technology for obtaining protein from microbial biomass and providing livestock breeding with new types of protein-vitamin concentrates. The Acetobacter methylicum strain, a producer of fodder protein, was used as an object of research. One of the stages of microbial protein production - the stage of isolation of microbial synthesis products - was studied. Protein isolation was carried out at the stationary phase of growth, the time of reaching which was determined by the experimental growth curve of bacterial culture. To intensify the stage of obtaining the final product in this study it is proposed to use an ampholytic surfactant - aminoxide (alkyldimethylamine oxide). It was found that at the concentration of surfactant in the culture liquid up to 1% adsorption of surfactant on the cell walls of bacteria takes place, while there is a destruction of cell walls and, accordingly, a decrease in the number of viable cells in the population of Acetobacter methylicum, which is probably associated with changes in the permeability of cell walls and their subsequent lysis. As a result, the number of viable cells decreases and the amount of released protein increases, which was monitored by the PI parameter (percentage of cell viability in the population). It was shown that for this surfactant the optimal concentration for cell destruction and protein release is 0.5% and the incubation time with surfactant is enough 15 minutes. Changing the surfactant concentration does not result in significant protein yield.

Разработка хлорсодержащих моюще-дезинфицирующих средств на основе амфолитного поверхностно-активного вещества – окиси алкилдиметиламина

Purpose. Compare the stability of sodium hypochlorite (according to the loss of active chlorine) in the presence of an ampholytic surfactant – alkyldimethylamine oxide (amine oxide) from different manufacturers. Materials and Methods. Determination of the mass fraction of active chlorine in the manufactured samples of detergents and disinfectants was carried out by the method of iodometric titration. Results. Three samples of a hypochlorite detergent-disinfectant using amine oxide from various manufacturers were studied: Aromox 14D-W970 (Nouryon company), Ammonyx LO (Stepan company), alkyl dimethylamine oxide (Monastyrikha Chemical Plant LLC). The initial content of active chlorine in all samples was 1.8% wt. The period of observation of the samples was 14 months. Hypochlorite detergent-disinfectant based on amine oxide produced by Monastyrikha Chemical Plant LLC can have a shelf life of not more than 6 months, based on Aromox 14D-W970 – 12 months, based on Ammonyx LO – 8 months. Conclusion. Thus, the stability of sodium hypochlorite (according to the loss of active chlorine) in the composition of detergents and disinfectants, which includes an ampholytic surfactant - amine oxide from various manufacturers, was studied. Taking into account the above factors, a hypochlorite detergent-disinfectant can be manufactured in two versions: the first is a cheaper product with a 6-month shelf life based on alkyl dimethylamine oxide LLC Monastyrikha Chemical Plant, the second is a product with a 12-month shelf life based on Aromox 14D-W970.

Performance enhancement of water and energy efficient foam dyeing and finishing through different foaming agents

ABSTRACT Foam dyeing and finishing is an ecofriendly alternative to conventional padding in textile processing. However, the generation and application of foam is a challenging task especially for wide range of dyes and chemicals due to technical and compatibility issues. In the foam dyeing and finishing process, foaming agent plays a central role. However, there is a lack of research on the compatibility of range of foaming agents with the range of different dyes and finishes. Therefore, in this research, foam was generated and optimized for seven different colorants including three reactive dyes, two direct dyes, and two pigments, and three different finishes including softener, oil and water repellent, and fire retardant using three different foaming agents separately. These foaming agents are alkyl dimethyl amine oxide, alkane sulfonate sodium salt, and ethoxylated decanol. Foam was successfully generated, optimized, and applied on the cotton fabric. Performance of the fabric samples treated with padding and three foaming agents for each dye and finish was evaluated. In most of the foam dyeing and foam finishing recipes, alkane sulfonate sodium salt-based foaming agent indicated the best dyeing and finishing properties and its performance was comparable with conventional padding in addition to significant savings of water, chemicals, and energy.

Stabilization of CO2-foams in brine by reducing drainage and coarsening using alkyldimethylamine oxides as surfactants

Producing CO2-foams in saline environments can be a great challenge in many industrial applications, since fast gas diffusion and reduction of electrical double layer promote fast coarsening and coalescence of bubbles. Amine oxides are zwitterionic surfactants that have been shown to improve foam stability by intermolecular hydrogen bonding, but have not been investigated for CO2-foams yet. This paper reports a study on the use of commercial alkyldimethylamine oxides (CxDAO) as foaming agents in brine for CO2-foams, based on the interactions present at the low pH imposed by the dissolution of the CO2 and the presence of salts. Despite the presence of salt and CO2 increased the protonation degree of amine oxide molecules, favoring hydrogen bonding, a significant improvement in foam stability was only observed when using the long chain surfactant (C14DAO). This behavior was attributed to the synergy between increased attractive hydrophobic interactions of alkyl chains and reduced repulsion among ionic surfactant heads, which led to formation of large surfactant aggregates in bulk, as demonstrated by the significant increase in viscosity of the aqueous phase. There was also a decrease in foam drainage and coarsening rates for the foams using C14DAO in brine, compared to results in deionized water, suggesting that formation of hydrogen bonds is not enough to arrest the destabilization in CO2-foams. Moreover, the linear rate of bubble growth obtained for these foams (∝t) was higher than that reported for N2– or air-foams (∝t1/2), likely due to the high solubility of CO2 in the aqueous phase, which accelerated the coarsening phenomena. The results of this work offer insight on the future design of foaming formulations for stabilizing CO2-foams in applications that require the use of high salinity brines, such as carbon sequestration and oil recovery.

Binding isotherms of surfactants used in detergent formulations to bovine serum albumin

Protein-surfactant interactions are the focus of extensive research due to their many applications in food technology and detergent industry. In this work, we investigate the interaction between bovine serum albumin (BSA) and five relevant surfactants to the cleaning industry, which differ in head group charge, namely: sodium alkyl ether sulphate (C12-C14 AE3S), Cocoamidopropyl amine-oxide (CapAO), alkyl dimethyl amine oxide (C12C14AO), octaethylene glycol monodecyl ether (C10EO8) and didecyldimethylammonium chloride (DDAC). The results collected with fluorescence emission spectroscopy highlight zwitterionic and nonionic surfactants have the lowest affinity for the protein, as their interaction does not result in protein denaturation. Instead, higher and mutually close binding constants are found for AE3S (anionic) and DDAC (cationic) due to the presence of electrostatic interactions between the surfactant heads and the charged residues of BSA. AE3S leads to irreversible protein unfolding. The case of DDAC is more complex and has been studied through a combination of fluorescence, DLS, PGSE-NMR and zeta-potential measurements. At low concentration DDAC binding neutralizes negatively charged residues present in BSA, causing a reversible flocculation of BSA after the isoelectric point (23 DDAC molecules per protein). Further DDAC adsorption, at 70 DDAC molecules per protein, leads to an excess of positive charge on the protein which restores electrostatic repulsions between BSA-surfactant complexes.

FOAM GYPSUM PRODUCTS BASED ON LOCAL BINDERS

Objectives. The problems of production of porous gypsum products on a local gypsum binder in the Karachay-Cherkess Republic are considered. Method. The study is based on the method of "dry" mineralization of foams, developed at the Moscow State University of Civil Engineering. As the source materials used plaster binder brand G-6 Ust-Dzhegutinsky plaster plant. An alkyl dimethylamine oxide (amine oxide) foaming agent was chosen as a foaming agent (PO). The choice of software is made taking into account its compatibility with the gypsum binder. At the same time, software of various classes was studied. Studies were performed to obtain foamed gypsum with an average density of 900 kg / m3. Result. A technology for the production of foam gypsum is proposed, based on the technology for the production of foam concrete by the method of “dry” mineralization of foams. The choice of foaming agent was made by comparative evaluation of the studied parameters of foaming agents of various classes. A technique has been developed for designing foamed gypsum formulations to produce products of a given average density. The technique includes the determination of the flow rate of HS, water flow and foaming agent, the determination of the B / T ratio. It was proposed to design the GHG compositions based on a given design average material density (), which in this case is equal to the consumption of dihydrate gypsum (CaSO42H2O). In the proposed method of obtaining foam – gypsum masses, the distinctive feature is the use of the technological properties of dense foams with low multiplicity. The boundary conditions for obtaining wall foam-gypsum products from a local gypsum binder that meet the requirements of GOST have been determined. Conclusion. Using modern research methods, it has been established that foam-hypo products from Ust-Dzhegutinsky gypsum of grade G-6 meet the requirements of standards for building heat-insulating and construction-heatinsulating products with a density of 400-1000 kg / m 3.

Branched alkyldimethylamine oxide surfactants: An effective strategy for the design of high concentration/low viscosity surfactant formulations

HypothesisThe rational design of branched-tail surfactants is a suitable strategy to obtain low-viscosity surfactant-rich isotropic aqueous mixtures with negligible effects on biodegradability. This opens a way to the design of concentrated (“water-free”) surfactant formulations, highly attractive for their ecological and economic benefits. ExperimentsThe aggregation behaviour of N,N-dimethyl-2-propylheptan-1-amine oxide (C10DAO-branched) in aqueous mixtures is investigated across the entire composition range by polarized optical microscopy, small angle X-ray and neutron scattering, electron paramagnetic resonance, and pulse-gradient stimulated echo nuclear magnetic resonance. The humidity scanning quartz crystal microbalance with dissipation monitoring technique is validated as a tool for the fast screening of surfactants phase behaviour. Furthermore, the shear viscosities and viscoelastic moduli of the systems are determined by rheological measurements. FindingsWith respect to the linear isomer, C10DAO-branched presents a much lower tendency to form lyotropic liquid crystalline phases. Except for a narrow composition and temperature range in which a lamellar structure is observed, C10DAO-branched aqueous mixtures are isotropic liquids whose microstructure changes, with increasing concentration, from micellar solutions to unstructured dispersions of hydrated surfactant molecules. Low-viscosity was found for all these mixtures, including the most concentrated ones. Thus, the introduction of a single short side-chain in the tail is demonstrated to be an effective approach to increase the active concentration in surfactant formulations.

Aquatic toxicity structure-activity relationships for the zwitterionic surfactant alkyl dimethyl amine oxide to several aquatic species and a resulting species sensitivity distribution

Amine oxide (AO) is a cationically charged surfactant at environmental pH and has previously been assessed in the OECD (Organization for Economic Cooperation and Development) High Production Volume (HPV) chemicals program. Typical of cationic chemicals, AO is highly aquatically toxic. In this study we vastly improve the knowledge of AO toxicity by developing acute Quantitative Structure Activity Relationships (QSARs) for an alga (Desmodesmus subspicatus), an invertebrate (Daphnia magna) and a fish (Danio rerio) using the appropriate array of OECD Test Guidelines. A chronic toxicity QSAR was also determined for the most sensitive taxon, Desmodesmus. Pure AO spanning the chain lengths of C8 to C16 were tested individually with trace analytical confirmation of exposures in all tests. The QSARs were all of high quality (R2 0.92–0.98) with slopes ranging from −0.338 to −0.484. QSARs were then used to normalize toxicity outcomes for a larger, previously published data set used in HPV, European REACH (Registration, Evaluation, and Authorization of Chemicals), and peer reviewed publications. Two additional species, Lemna gibba (macrophyte) and Ankistrodesmus falcatus (alga) were studied in exposures to dodecyl (C12) AO to provide sufficient taxonomic diversity to conduct a Species Sensitivity Distribution (SSD) analysis. The SSD 5th percentile hazardous concentration (HC5) to C12 AO was found to be 0.052mg/L which is similar to an existing AO 28-d, 3-community periphyton community bioassay normalized to C12 AO (No-observed-effect-concentration or NOEC=0.152mg/L). The statistical properties of the SSD was probed suggesting that new studies of additional taxa would be required that were at least 10-fold more sensitive than the most sensitive taxon to move the HC5 lower by a factor of 3. The overall AO hazard assessment suggests a large margin of safety relative to published environmental exposure data.

Light-responsive multillamellar vesicles in coumaric acid/alkyldimethylamine oxide binary systems: Effects of surfactant and hydrotrope structures

Herein, we report a series of novel light-responsive multilamellar vesicles based on the surfactant/hydrotrope binary systems. The phase behaviors of alkyldimethylamine oxide (CmDMAO, m=10, 12, 14) and trans-coumaric acid (trans-CA) isomerides, including trans-ortho-coumaric acid (trans-OCA), trans-meta-coumaric acid (trans-MCA) and trans-para-coumaric acid (trans-PCA), show that the multilamellar vesicle (MLV) formation region is commonly presented in the trans-CA/CmDMAO systems except trans-PCA/C12DMAO. Moreover, the molecular structures of CmDMAO and trans-CA affect the multilamellar vesicle formation region significantly. Generally speaking, the bigger the m, the larger the MLV region. Various techniques such as rheology, polarized optical microscopy (POM), 1H NMR, 2H NMR, cryogen transmission electron microscopy (cryo-TEM) and freeze-fracture transmission electron microscopy (FF-TEM) are used to characterize the aggregate structures. The multilamellar vesicles can transform into a homogeneous and transparent micelle phase or a two-phase system in the trans-OCA/CmDMAO binary systems under UV light irradiation, which depends on the chain length of CmDMAO and the molar ratio of [trans-OCA]/[CmDMAO]. Specifically, the light-stimuli response of multilamellar vesicles in the trans-OCA/C12DMAO system is representatively studied in detail. UV–vis spectra and 1H NMR measurements illustrate that the light-induced trans-OCA to cis-OCA isomerization is essential during the transitions and the light-induced two-phase formation is attributed to the enrichment of surfactants, because the trans-cis isomerization can not only strengthen the hydrophilicity of cis-OCA but also increase the steric hindrance between cis-OCA and C12DMAO, and thereby altering the morphology of aggregate and the rheological response of bulk phase significantly.

Controlled compaction and decompaction of DNA by zwitterionic surfactants

Abstract Controlled compaction and decompaction of DNA by zwitterionic surfactants, alkyldimethylamine oxides (CnDMAO, n = 10, 12, and 14), were investigated by various analytical tools. It was found that DNA could effectively be compacted by cationic micelles of CnDMAOH+ which were produced by the protonation of CnDMAO in acidic media leading to the formation of water-insoluble CnDMAOH+/DNA complexes. The DNA molecules were compacted at pH 4–5 when the concentration of C10DMAOH+, C12DMAOH+, and C14DMAOH+ reached 8.0, 1.6, and 0.9 mmol L−1, respectively. Interestingly, the precipitates of CnDMAOH+/DNA complexes can re-dissolve which indicated that the DNA molecules were released from the complexes by regulating the pH of the solution to ∼4 and increasing the surfactant concentration to 40, 9.0, and 1.8 mmol L−1 for C10DMAOH+, C12DMAOH+, and C14DMAOH+, respectively. This phenomenon was attributed to the hydrogen bonding formed between cationic CnDMAOH+ and zwitterionic CnDMAO species. These hydrogen-bonded species screen the electrostatic forces between the positively charged CnDMAOH+ micelles and the negatively charged backbones of DNA. Our results demonstrated that the release of DNA from the CnDMAOH+/DNA precipitates depended on the concentration of cationic CnDMAOH+ and the pH of the solution. Compared with the conventional release of DNA by the addition of β-cyclodextrin, the present strategy allowed for a specific controlled release, which favored the penetration of DNA into cells and could protect the DNA molecules from nucleases degradation.

Thermo-reversible capture and release of DNA by zwitterionic surfactants.

The thermo-reversible capture and release of DNA were studied by the protonation and deprotonation of alkyldimethylamine oxide (CnDMAO, n = 10, 12 and 14) in Tris-HCl buffer solution. DNA/C14DMAO in Tris-HCl buffer solution with pH = 7.2 is transparent at 25 °C, indicating that DNA molecules exist mainly in individuals and the binding of C14DMAO is weak. With the increase of temperature, the pH of the buffer solution continuously decreases, which leads to protonation of C14DMAO (C14DMAO + H(+)→ C14DMAOH(+)) and an obvious increase of the turbidity of the samples. This indicates a stronger binding of the protonated C14DMAOH(+) to DNA. Further investigations demonstrated the formation of DNA/C14DMAOH(+) complexes, in which the stretched DNA molecules are effectively compacted as evidenced from UV-vis absorptions, circular dichroism (CD) measurements, atomic force microscopy (AFM) observations, dynamic light scattering (DLS) measurements and agarose gel electrophoresis (AGE). Interestingly, when the temperature is turned back to 25 °C, the compacted DNA molecules can fully recover to the stretched conformation. This cycle can be repeated several times without obvious loss of efficiency. The effect of the chain length of CnDMAO has also been investigated. When C14DMAO was replaced by C12DMAO, similar phenomena can be observed with a slightly higher critical surfactant concentration for DNA compaction and a slightly lower pH of Tris-HCl buffer solution with pH = 6.8. For the DNA/C10DMAO system, however, no DNA compaction was observed even in Tris-HCl buffer solution with a much lower pH and a much higher C10DMAO concentration. The negative charges of DNA molecules can easily be neutralized by positive charges of cationic CnDMAOH(+) (n = 12 and 14) micelles. DNA was compacted and then insoluble DNA/CnDMAOH(+) complexes were formed. Because of the much higher critical micelle concentration (cmc) of the shorter chain length C10DMAOH(+), cationic C10DMAOH(+) micelles cannot form under the studied condition to compact DNA. The strategy may provide an efficient and alternative approach for stimuli-responsive gene therapy and drug release.

Is the incidence of aliphatic amine-induced occupational rhinitis and asthma underestimated?

Amines, some of which are known to cause asthma, are frequently present in the work environment, but are rarely identified as being responsible for occupational rhinitis (OR) or asthma (OA). However, amine-induced OR/OA may be underreported. To discuss this hypothesis, we report a series of patients with positive amine-specific nasal provocation test (NPT). Review of the medical charts of 37 patients with OR (alone or associated with asthma), submitted to a NPT with an aliphatic or alicyclic amine (except for EDTA) present in a product used at work. Most patients worked in the healthcare sector or for a cleaning company. Amines were mostly present in cleaning products. Seven patients had a positive NPT. NPTs were positive for the following amines: bis(aminopropyl)laurylamine, C12-C18 alkyldimethylamine oxides, bis(2-hydroxyethyl)tallowamine oxides, 3-dimethylaminopropylamine, 2,2'-dimethyl-4,4'-methylene-bis(cyclohexylamine), lauryldimethylamine oxide. NPTs were negative for the following amines: monoethanolamine, diethanolamine, triethanolamine, isopropanolamine, triethylamine, triethylenetetramine, aminopropyltriethoxysilane, alkylpropylenediamineguanidine acetate. The frequency of amine-induced OR/OA may be underestimated, particularly when cleaning products are incriminated. Comprehensive investigation of all cases is mandatory to ensure an efficient prevention policy and consequently a good clinical and socio-occupational prognosis of occupational respiratory disease.

The antimicrobial agent C31G is effective for therapy for HSV-1 ocular keratitis in the rabbit eye model

The amphoteric C31G solution contains equimolar alkyl dimethlyglycine and alkyl dimethyl amine oxide buffered with citric acid. C31G acts as a broad spectrum antiviral and an antibacterial. No previous in vivo studies have been done to test C31G in an animal model of HSV-1 ocular keratitis. We assessed the anti-herpetic activity of C31G in the rabbit eye model using three treatment groups: (1) 1% trifluorothymidine (TFT); (2) 0.25% C31G plus 0.5% hydroxypropyl methylcellulose (HPMC); and (3) vehicle, 0.5% HPMC. Scarified rabbit corneas were inoculated with the HSV-1 strain McKrae. On post inoculation (PI) day 3, rabbits were placed in three balanced groups based on slit-lamp examination (SLE) scores. Treatment began on PI day 3, five times a day for five consecutive days. In addition to the daily, masked SLE scoring, the eyes were assessed daily for stromal opacity, scleral inflammation, neovascularization, eyelid inflammation, inflammatory discharge, and epiphora. C31G and TFT were very effective in reducing the lesions and pathogenesis associated with HSV-1 ocular keratitis. The vehicle control scores were significantly higher and did not effectively treat HSV-1 keratitis. C31G has the potential to be used to treat herpetic keratitis as well as other herpetic topical lesions in humans.

Balance of Coordination and Hydrophobic Interaction in the Formation of Bilayers in Metal-Coordinated Surfactant Mixtures

Metal-ligand coordination and hydrophobic interaction are two significant driving forces in the aggregation of mixtures of M(n+) surfactants and alkyldimethylamine oxide (CnDMAO) in aqueous solutions. The coordinated systems exhibit rich aggregation behavior. This study investigated the effect of M(n+) ions (Zn(2+), Ca(2+), Ba(2+), Al(3+), Fe(3+), La(3+), Eu(3+), and Tb(3+)) and hydrophobic chains (hydrocarbon and fluorocarbon) on the formation of metal-coordinated bilayers. We found that fluorocarbon chains and branched hydrocarbon chains are preferable to the corresponding linear hydrocarbon chains for the formation of an Lα phase. Moreover, Lα phases formed by fluorocarbon chains exhibited higher viscoelasticity than ones formed by the hydrocarbons, and the bilayers formed by branched chains were rather flexible, revealing obvious undulation. The construction of bilayers was also strongly affected by metal ions due to their variable coordination ability with CnDMAO. Our results contribute to the understanding of the formation of metal-coordinated bilayers, which is driven by the interplay of noncovalent forces.

Solubilisation of camptothecin by nonionic surfactants and alkyldimethylamine oxides

Abstract The solubilisation of poorly soluble antineoplastic drug camptothecin by nonionic surfactants (polysorbates and octylphenol ethoxylates) and alkyldimethylamine oxide surfactants with the alkyl chain length 8 to 16 carbon atoms was investigated. The hydrophobicity of the solubilising agent turned out to be the primary structural parameter controlling the solubility efficiency of camptothecin in an aqueous solution. The quantitative parameter of solubilisation (drug loading coefficient) provided values in the range of 0.1–1.2% and 0.1–1.0% for alkyldimethylamine oxides and nonionic surfactants, respectively. The decreasing number of oxyethylene units and the extension of the hydrophobic part of nonionic surfactant molecule resulted in the increase of camptothecin solubility. From the dynamic light scattering measurements, the hydrodynamic diameter values of camptothecin-loaded alkyldimethylamine oxide and nonionic micelles were found in the range of 4–42 nm and 5–120 nm, respectively. The experimental values confirmed the increase in micellar size with the increasing alkyl chain length. The values of the packing parameter of camptothecin-loaded dodecyldimethylamine oxide micelles indicate their spherical shape at all the investigated surfactant concentrations. A simple computer model of camptothecin-loaded dodecyldimethylamine oxide micelle provided the diameter of the structure cross section which is consistent with the experimental values.

Temperature regulated supramolecular structures via modifying the balance of multiple non-covalent interactions

Gelation of lithocholic acid (LCA) mixed with zwitterionic alkyldimethylamine oxide, (CnDMAO, n = 10, 12, 14, 16, and 18), in water was detected. Hydrogels can only form at an appropriate hydrophilic–hydrophobic balance condition (n = 12, 14, and 16) with the highest gelation capability at n = 12. Microstructures of hydrogels were determined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) observations, indicating that the hydrogels are formed by helically intertwined fibrils. The formation of the hydrogel fibrils was suspected to be driven by a delicate balance of multiple non-covalent interactions including hydrogen bonding, electrostatic interaction, hydrophobic interaction, and the steric effect of LCA molecules. It is very interesting that temperature changes alone can induce a reversible transition between the helical fibrils and vesicle bilayers. The breakage or reconstruction of the hydrogen bonds produced by the temperature change determined the phase structure transition, i.e., the temperature change could modify the balance of the weak interactions for the formation of hydrogels. The observation of modification of supramolecular structures via temperature change may provide an efficient strategy for the phase structure transition and also may find potential applications in biosensors, shape memory, templating of functional molecular materials, etc.

Effect of Hydrophilic Groups of Ca Surfactants and Hydrophobic Chains of CnDMAO on Coordinated Vesicle Formation

The effects of hydrophilic headgroups of Ca surfactants, calcium dodecylsulfate (Ca(DS)(2)), calcium dodecylsulfonate (Ca(DSA)(2)), and calcium laurate (CaL(2)) and hydrophobic chains of alkyldimethylamine oxide (C(n)DMAO, n = 12, 14, 16) on the formation of Ca(2+)-ligand coordinated vesicles was investigated in detail. On the basis of phase behavior studies, rheological properties and freeze-fracture transmission electron microscope (FF-TEM) images were measured. Quite different phase behaviors were observed in different surfactant systems. For a Ca surfactant with a highly polar group, Ca(DS)(2), vesicles were observed in all Ca(DS)(2)/C(n)DMAO (n = 12, 14, and 16) systems, whereas for Ca surfactant with lower polar group, Ca(DSA)(2), vesicles can form in Ca(DSA)(2)/C(n)DMAO systems of n = 14 and 16 but not for n = 12. For CaL(2), the surfactant with the least polar group, vesicles form only in the CaL(2)/C(16)DMAO system. The results demonstrate that in the systems formed by Ca surfactants and C(n)DMAO, the formation of vesicles is driven not only by interaction between Ca(2+) and the N → O groups of C(n)DMAO but also by electrostatic and hydrophobic interactions. Vesicles prefer to form in Ca surfactants with highly polar headgroups and C(n)DMAO with long chain length.

Electrochemical Synthesis of Zinc Nanoparticles via a Metal−Ligand-Coordinated Vesicle Phase

Two salt-free Zn(2+)-ligand-coordinated vesicle phases were prepared from the mixtures of alkyldimethylamine oxide (C(n)DMAO, n = 14 and 16, i.e., C(14)DMAO and C(16)DMAO) and zinc laurate [(CH(3)(CH(2))(10)COO)(2)Zn] in aqueous solution. The two salt-free Zn(2+)-ligand-coordinated vesicle phases were subsequently used as the templating media for fabricating zinc nanoparticles on an indium-doped tin oxide (ITO) electrode via electrodeposition. Influence of temperature, direct current density, and composition of the surfactant mixtures on the average diameter and size distribution of Zn nanoparticles was investigated in more detail. The structure of Zn@ITO was determined by scanning electron microscope and energy-dispersive X-ray spectroscopy analysis. Monodispersed Zn nanoparticles on ITO electrode (ZnNPs@ITO) with different average diameters were obtained, and the distribution can be controlled. Finally, ZnO nanostructures on the ITO substrate were prepared from the as-synthesized Zn@ITO nanoparticles through electrochemical surface oxidation. The preparation of nanostructured Zn and ZnO particles by our established method may pave the way for a new templating route from metal-ligand-coordinated vesicles.

Phase behavior, rheological properties, and vesicles of alkyldimethylamine oxide and fluorinated acidic surfactant mixtures

Weakly basic alkyldimethylamine oxide (CnDMAO, n = 12, 14, and 16) molecules can be protonated to form a cationic surfactant, CnDMAOH+, by an acidic fluorocarbon surfactant, 8-2-fluorotelomer unsaturated acid (C7F15CFCHCOOH), to produce the salt-free cationic and anionic (catanionic) surfactant mixtures in aqueous solution. These comparative studies on phase behavior and rheological properties of these salt-free catanionic hydrocarbon–fluorocarbon surfactant mixtures in detail clearly indicate the existence of a birefringent Lα-phase for C12DMAO/C7F15CFCHCOOH and C14DMAO/C7F15CFCHCOOH systems at 25.0 ± 0.1 °C. However, the birefringent Lα-phase of C16DMAO/C7F15CFCHCOOH system exist at 60.0 ± 0.1 °C. The birefringent Lα-phase which consists of uni- and multilamellar vesicles, and oligovesicular vesicles is independent of the hydrocarbon chain of CnDMAO at controlled temperatures. The vesicles were demonstrated by cryo-transmission electron microscopy (cryo-TEM) and negative-staining TEM images, in which pliability of the bilayer membranes decreases with the increasing length of hydrogenated chains of hydrocarbon surfactants. The formation of the salt-free catanionic Lα-phase consisting of vesicles could be induced by the strong electrostatic interaction between the cationic hydrocarbon C14DMAOH+ and the anionic fluorocarbon C7F15CFCHCOO−, C14DMAOH+ is produced through acid–base reaction of C14DMAO and C7F15CFCHCOOH. The rheological properties of micelles and vesicles in the three mixture systems were measured, which provided much more information about the hydro- and fluorocarbon surfactant mixtures. The size distribution and structural transition of these similar systems but having different length chains of hydrocarbon surfactants were studied by dynamic light scattering (DLS) and 1H and 19F NMR spectroscopy.

Protonation Behavior and Stability of Micelles of N-Lauroylaminoalkyl-Dimethylamine Oxides-Effects of Added Salt Concentration and Spacer Length

The protonation behavior and the stability of micelles of N-lauroylaminopropyl-N',N'- dimethylamine oxide (C12AmCn; n=3) were studied by the hydrogen ion titration and the equilibrium surface tension measurement. The surface potential of C12AmC3 micelles estimated from the results of hydrogen ion titration was lower than that of dodecyldimethylamine oxide micelles at added NaCl concentration, C(S), of 0.1M. The critical micelle concentration (cmc) estimated from surface tension measurements revealed that a reversal of the stability of the cationic and the nonionic micelles of C12AmC3 takes place in the range of C(S) higher than about 0.2M, that is, the cationic micelles become more stable than the nonionic ones in the range C(S) >or= 0.2M. In addition, the surface tension measurements were carried out for C12AmCn with different spacer length, n, ranging from 2 to 6 methylene units at C(S) = 0.1M. The cmc values of nonionic species were kept at almost constant for n <or= 4, while they decreased with n for n >or= 4. The cmc values of cationic species also tended to decrease with n for n >or= 4. These results were compared with those obtained for alkyldimethylamine oxides, and the effect of amide group and spacer groups introduced into amine oxide surfactants was discussed.