Double-tailed Cationic Surfactant Research Articles

An HLD framework for cationic ammonium surfactants

The Hydrophilic-Lipophilic Difference (HLD) model can be described by additive contributions accounting for the effect of the oil and surfactant nature, temperature, ionic strength, and so on. The first step to build an HLD framework for a surfactant class is to have Winsor III phase equilibria in a restricted range of formulation variables. In this respect, anionic and nonionic surfactants are well suited for an HLD study. On the contrary, it is difficult achieve for pure cationic surfactant Winsor III phase equilibria without the addition of alcohols and this has precluded the extension of the HLD to cationic surfactants. In the present contribution, we first propose a system based on a blend of single-tailed and double-tailed cationic surfactant to study the oil contribution, and then we afforded the determination of the surfactant contribution trough an experimental approach (the “HLD-titration”) that is especially tailored for systems displaying a wide range of existence of Winsor III phase equilibria. HLD-titration results confirmed the ionic strength contribution to HLD as a logarithmic function of salinity for cationic-based microemulsions similarly to anionic ones. However, the oil carbon number contribution is almost four-fold larger ( k ​= ​0.7 ​± ​0.1) with respect to anionic surfactants. A clearing point was observed in correspondence of the Winsor III phase equilibria under stirring. This approach allows us the determination of the so-called characteristic curvature ( Cc ), i.e. the term describing the surfactant nature contribution to the film curvature, of the cationic surfactant. Finally, the method was adopted to determine Cc values of 7 quaternary ammonium surfactants differing in the polar heads nature and further three amine oxide surfactant at pH ​= ​1 where they are protonated.

Self-Assembled Magnetic Viruslike Particles for Encapsulation and Delivery of Deoxyribonucleic Acid.

Developing nontoxic artificial carriers for stimuli-responsive capture, transport, and delivery of biomolecules is of immense scientific interest. Herein, for the first time, we synthesize a double-tailed cationic surfactant, (C16H33)2(CH3)2N+[FeCl3Br]-, which possesses magnetic properties [magnetic surfactants (Mag-Surfs)]. The time-dependent formation of virus-shaped hybrid mixed assemblies of polyoxometalates (POMs) {Mo72Fe30}/Mag-Surf with hollow-shell structures is followed. These structures serve well as robust high-surface-area shuttles, which can be manipulated with applied magnetic fields. By using cationic Mag-Surfs, the anionic POMs and DNA can be complexed in these ternary mixtures. These virus-shaped complexes act as nanoanchors and nanomotors, which can be utilized for binding, anchoring, and delivery of biomolecules, such as DNA. It is found that they have a good absorption capacity for DNA and myoglobin over 24 h, after application of a magnetic field. The realization of magnetic virus-shaped {Mo72Fe30}/Mag-Surf spheres may open possibilities for designing other functional nanoparticles, allowing effective control over the delivery/separation of biomolecules.

Fabric Softener-Cellulose Nanocrystal Interaction: A Model for Assessing Surfactant Deposition on Cotton.

There is currently a renewed interest for improving household and personal-care formulations to provide more environment-friendly products. Fabric conditioners used as softeners have to fulfill a number of stability and biodegradability requirements. They should also display significant adsorption on cotton under the conditions of use. The quantification of surfactant adsorption remains however difficult because the fabric-woven structure is complex and deposited amounts are generally small. Here, we propose a method to evaluate cellulose-surfactant interactions with increased detection sensitivity. The method is based on the use of cellulose nanocrystals (CNCs) in lieu of micron-sized fibers or yarns, combined with different techniques, including light scattering, optical and electron microscopy, and electrophoretic mobility. CNCs are rod-shaped nanoparticles in the form of 200 nm laths that are negatively charged and can be dispersed in bulk solutions. In this work, we use a double-tailed cationic surfactant present in fabric softener. Results show that the surfactants self-assemble into unilamellar, multivesicular, and multilamellar vesicles, and the interaction with CNCs is driven by electrostatics. Mutual interactions are strong and lead to the formation of large-scale aggregates, where the vesicles remain intact at the cellulose surface. The technique developed here could be exploited to rapidly assess the fabric conditioner efficiency obtained by varying the nature and content of their chemical additives.

Self-patterning porous films of giant vesicles of {Mo72Fe30}(DODMA)3 complexes as frameworks

This work describes the preparation and properties of self-patterning porous films consisting of giant vesicles formed by a 2.5-nm-diameter, polyoxometalate (POM) cluster {Mo72Fe30} macroanion, and a double-tailed cationic surfactant dimethyldistearylammonium bromide (DODMABr) in CHCl3–CH3OH mixture solvent (VCHCl3: VCH3OH=3:1). These inverse vesicles with the diameter in the range of 0.45~1.3μm in organic solution and the porous films consisting of the giant vesicles of the {Mo72Fe30}(DODMA)3 complexes were characterized by SEM, TEM, XPS and AFM observations. Self-patterning of these giant vesicles into porous films that are highly ordered honeycomb films on solid surfaces can survive drying as the frameworks are firstly studied in detail. Water contact angle measurements proved that the porous films of {Mo72Fe30}(DODMA)3 vesicles were endowed hydrophobic property from the hydrophilic surface. This porous film materials consisting of giant vesicles may be promising new options in many fields like photoelectrochemistry, sterilization, template, catalysis, in-situ synthesis.

Rheological studies of thermotropic phase transitions in cationic vesicle suspensions: Instantaneous “jamming” and aging behavior

Cationic double-tailed surfactants exhibit a rich thermotropic phase behavior. Here, we examine the effect of thermal gradients and processing history on the rheology and microstructure of concentrated multilamellar vesicle (MLV) suspensions made from a double-tailed cationic surfactant (diC18:0 DEEDMAC), whose bilayers are in the crystalline (solid) state at room temperature. The rheological properties of the MLV suspensions are found to be strongly dependent on the thermal behavior of the constituent bilayer with the visco-elastic moduli exhibiting a nonmonotonic variation with temperature, initially increasing by 1–2 orders of magnitude at an intermediate temperature, before rapidly decreasing at higher temperatures. Furthermore, when subject to a contraction flow through an extruder, above the main phase transition temperature of the bilayers, the suspensions instantaneously transform into a “jammed,” glassy-state at the extruder outlet. The glassy dispersions behave like stiff gel-like materials, having visco-elastic moduli that are several orders of magnitude higher than their unextruded counterparts. We probe mechanisms leading to the formation and subsequent aging of the jammed suspensions and show that the microstructural evolution of the extruded “gels” on aging is qualitatively different from that of the unextruded suspensions.

Direct Measurements of Effect of Counterion Concentration on Mechanical Properties of Cationic Vesicles

Theoretical analyses of charged membranes in aqueous solutions have long predicted that the electric double layer surrounding them contributes significantly to their mechanical properties. Here we report the first, direct experimental measurements of the effect of counterion concentration on the bending and area expansion modulus of cationic surfactant vesicles. Using the classical technique of micropipet aspiration coupled with a modified experimental protocol that is better suited for cationic vesicles, we successfully measure the mechanical properties of a double-tailed cationic surfactant, diethylesterdimethyl ammonium chloride (diC18:1 DEEDMAC) in CaCl2 solutions. It is observed that the area expansion modulus of the charged membrane exhibits no measurable dependence on the counterion concentration, in accordance with existing models of bilayer elasticity. The measured bending modulus, however, is found to vary nonmonotonically and exhibits a minimum in its variation with counterion concentration. The experimental results are interpreted based on theoretical calculations of charged and bare membrane mechanics. It is determined that the initial decrease in bending modulus with increasing counterion concentration may be attributed to a decreasing double layer thickness, while the subsequent increase is likely due to an increasing membrane thickness. These mechanical moduli measurements qualitatively confirm, for the first time, theoretical predictions of a nonmonotonic behavior and the opposing effects of ionic strength on the bending rigidity of charged bilayers.

Molecular Dynamics Study of Catanionic Bilayers Composed of Ion Pair Amphiphile with Double-Tailed Cationic Surfactant

The physical stability of catanionic vesicles is important for the development of novel drug or DNA carriers. For investigating the mechanism by which catanionic vesicles are stabilized, molecular dynamics (MD) simulation is an attractive approach that provides microscopic structural information on the vesicular bilayer. In this study, MD simulation was applied to investigate the bilayer properties of catanionic vesicles composed of an ion pair amphiphile (IPA), hexadecyltrimethylammonium-dodecylsulfate (HTMA-DS), and a double-tailed cationic surfactant, ditetradecyldimethylammonium chloride (DTDAC). Structural information regarding membrane elasticity and the organization and conformation of surfactant molecules was obtained based on the resulting trajectory. Simulation results showed that a proper amount of DTDAC could be used to complement the asymmetric structure between HTMA and DS, resulting in an ordered hydrocarbon chain packing within the rigid membrane observed in the mixed HTMA-DS/DTDAC system. The coexistence of gel and fluid phases was also observed in the presence of excess DTDAC. MD simulation results agreed well with results obtained from experimental studies examining mixed HTMA-DS/DTDAB vesicles.

Facile Preparation of Organic Nanoparticles by Interfacial Cross-Linking of Reverse Micelles and Template Synthesis of Subnanometer Au−Pt Nanoparticles

A single- and a double-tailed cationic surfactant with the triallylammonium headgroup formed reverse micelles (RMs) in heptane/chloroform containing a small amount of water. The reverse micelles were cross-linked at the interface upon UV irradiation in the presence of a water-soluble dithiol cross-linker and a photoinitiator. The resulting interfacially cross-linked reverse micelles (ICRMs) of the single-tailed surfactant aggregated in a solvent-dependent fashion, whereas those of the double-tailed were identical in size as the corresponding RMs. The ICRMs could extract anionic metal salts, such as AuCl(4)(-) and PtCl(6)(2-), from water into the organic phase. Au and Pt metal nanoparticles were produced upon reduction of metal salts. The covalent nature of the ICRMs made the template synthesis highly predictable, with the size of the metal particles controlled by the amount of the metal salt and the method of reduction. Nanoalloys were obtained by combining two metal precursors in the same reaction. Reduction of the ICRM-entrapped aurate also occurred without any external reducing agents, and the gold nanoparticles differed dramatically from those obtained through sodium borohydride reduction. The same template allowed the preparation of luminescent Au(4), Au(8), and Au(13)-Au(23) clusters, as well as gold nanoparticles several nanometers in size, simply by using different amounts of gold precursor and reducing conditions.

Structure–activity relationship of cyclodextrin/biocidal double-tailed ammonium surfactant host–guest complexes: Towards a delivery molecular mechanism?

In aqueous solution, the biocidal double-tailed cationic surfactant, di- n-decyl-dimethyl-ammonium chloride can form inclusion complexes with various cyclodextrins (α- CD, β- CD, γ- CD, HP-α- CD, HP-β- CD and CM-β- CD). A physicochemical study has been performed to investigate the association parameters of these host–guest complexes by combining the use of ammonium and chloride selective electrodes, NMR spectroscopy and molecular modeling. stoichiometries, equilibrium constants and geometries were determined by resorting to a specific algorithm. The antimicrobial activity of the encapsulated ammonium surfactant was compared with that of the free ammonium showing three different behaviors depending on the cyclodextrin. The close relationship between the complex structure and the biocidal activity is used to propose a delivery molecular mechanism.

Langmuir monolayer behavior of an ion pair amphiphile with a double-tailed cationic surfactant

The spread or Langmuir monolayer behavior of an ion pair amphiphile (IPA), hexadecyltrimethylammonium-dodecylsulfate (HTMA–DS), with a double-tailed cationic surfactant, dihexadecyldimethylammonium bromide (DHDAB), at the air/water interface was analyzed with surface pressure–area isotherms, area relaxation curves, and Brewster angle microscope (BAM) images. The surface pressure–area isotherms showed that with increasing the DHDAB molar ratio, X DHDAB, spread monolayers of HTMA–DS with DHDAB became rigid. In addition, unreasonably small limiting areas per alkyl chain of the molecules in the monolayers were found, especially at X DHDAB = 0.5, implying the molecular loss from the monolayers at the interface. For spread HTMA–DS/DHDAB monolayers at the interface, a new IPA, DHDA–DS, was proposed to form through the displacement of HTMA + from HTMA–DS by DHDA +, leaving HTMA + dissociated. The formation of DHDA–DS and the desorption of dissociated HTMA + upon the interface compression were supported by the results obtained from designed monolayer experiments with BAM observations, and were discussed by considering the hydrophilicity, packing efficiency, and headgroup charge characteristic of the species. Moreover, the area relaxation curves of spread HTMA–DS/DHDAB monolayers suggested that the formation of DHDA–DS was strongly related to the improved monolayer stability at the interface, which may have implications for the DHDAB-enhanced physical stability of catanionic vesicles composed of HTMA–DS.

Synthesis and characterization of a novel double-tailed cationic surfactant

Abstract A novel double-tailed cationic surfactant, N,N′-didodecylacetamidinium bicarbonate, was prepared by reacting dimethylacetamide dimethyl acetal with dodecylamine, followed by reacting with dry ice. MSD, FTIR, 1H NMR, 13C NMR, 2D-NMR were used to confirm its structure. The surfactant reduced the surface tension of pure water to 24.7 mN m−1 and its critical micelle concentration was 8.75 × 10−5 M. Formation of vesicle was also observed.

Electrochemical Control of Vesicle Formation with a Double-Tailed Cationic Surfactant Bearing Ferrocenyl Moieties

We already reported spontaneous vesicle formation in aqueous solutions of bis(11-ferrocenyl(undecyl))dimethylammonium bromide (11-BFDMA), a newly synthesized ferrocene-modified double-chain-type cationic surfactant (Kakizawa, Y.; Sakai, H.; Nishiyama, K.; Abe, M. Langmuir 1996, 12, 921.). We have examined in this study electrochemical control of vesicle formation of 11-BFDMA using the redox reaction of ferrocenyl groups in their molecules. Static light scattering, conductivity, and cyclic voltammogram measurements on the solution revealed that vesicles made of the reduced form of 11-BFDMA disintegrate and change into smaller molecular aggregates including micelles through oxidation of ferrocenyl groups. Oxidation of ferrocenyl groups also caused a remarkable decrease in the solubilization equilibrium constant for benzene in 11-BFDMA solution and release into the bulk phase of benzene solubilized in bimolecular layers of 11-BFDMA vesicles. In addition, glucose entrapped in the inner aqueous phase of the ve...

CATIONIC VESICLE PRECURSORS AS RETARDING AND LEVELLING AGENTS FOR THE DYEING OF ACRYLIC FIBRES

Abstract The use of a double-tailed cationic surfactant as additive in the dyeing of polyacrylonitrile with cationic dyes is proposed. Single-tailed colorless cations usually compete with the dyes for the anionic sites within the fibre and at the fibre surface, thus retarding and giving levelness to the dyeings. A set of comparative tests has shown that di-methyl-di-dodecylammonium chloride (DDDAC) behaves better by far, as retarding and levelling agent, than commercially well known single-tailed cations.