Double-chain Cationic Surfactant Research Articles

Effect of Electrolytes on Solution and Interfacial Behaviors of Double Chain Cationic-Nonionic Surfactant Mixtures for Hydrophobic Surface Wetting and Oil/Water Emulsion Stability Applications.

The solution behaviors of the binary mixture of double chain cationic surfactant didodecyldimethylammonium bromide (DDAB) with nonionic surfactants of varied head groups, EO-9 and EO-40, in the presence and absence of electrolytes were studied and found nonideal behavior. The different physicochemical properties such as Gibb's surface excess (Γ), minimum area per molecule (Amin), and interaction parameters at bulk (βM) and interface (βσ) were calculated. In the presence of nonionic surfactants, lowering of CMC, CVC, and surface tension at these two concentrations of DDAB were observed. The βM and βσ values indicate strong interaction between DDAB and EO-40 mixed system. Further, addition of electrolytes to the mixed systems show increased interaction and change of physicochemical properties because of the combination of electrical and salting out effects.

Effects of the Method of Preparation and Dispersion Media on the Optical Properties and Particle Sizes of Aqueous Dispersions of a Double-Chain Cationic Surfactant.

As inferred from visual observations and turbidity measurements, the average radius of the unilamellar vesicles formed in water from the cationic double-chain surfactant didodecyldimethylammonium bromide (DDAB) varies with the method of preparation, being ∼24 nm after sonication (SS method) and ∼74 nm after extrusion/ultrafiltration (SE method). The radii were larger when the vesicles were produced in 10 mM NaBr, ∼65 nm for the SS method and ∼280 nm for the SE method. The specific turbidity, or turbidity per unit path length divided by the surfactant weight fraction, w, of these vesicular dispersions increased with decreasing w until a constant value was reached at w*, which depends on the preparation method and the dispersion medium. The constant specific turbidities are indicative of single and independent scattering and were used to estimate vesicle radii by solving the specific turbidity equations derived for the Rayleigh-Debye-Gans (RDG) regime. Two turbidity equations were used, one accounting for absorbance errors due to some scattered light reaching the detector and another with no correction. Estimates of the average distances between the vesicles and their corresponding Debye lengths were obtained for evaluating the importance of intervesicle electrostatic interactions, which could lead to dependent scattering at higher weight fractions.

Double-Chain Cationic Surfactants: Swelling, Structure, Phase Transitions and Additive Effects.

Double-chain amphiphilic compounds, including surfactants and lipids, have broad significance in applications like personal care and biology. A study on the phase structures and their transitions focusing on dioctadecyldimethylammonium chloride (DODAC), used inter alia in hair conditioners, is presented. The phase behaviour is dominated by two bilayer lamellar phases, Lβ and Lα, with “solid” and “melted” alkyl chains, respectively. In particular, the study is focused on the effect of additives of different polarity on the phase transitions and structures. The main techniques used for investigation were differential scanning calorimetry (DSC) and small- and wide-angle X-ray scattering (SAXS and WAXS). From the WAXS reflections, the distance between the alkyl chains in the bilayers was obtained, and from SAXS, the thicknesses of the surfactant and water layers. The Lα phase was found to have a bilayer structure, generally found for most surfactants; a Lβ phase made up of bilayers with considerable chain tilting and interdigitation was also identified. Depending mainly on the polarity of the additives, their effects on the phase stabilities and structure vary. Compounds like urea have no significant effect, while fatty acids and fatty alcohols have significant effects, but which are quite different depending on the nonpolar part. In most cases, Lβ and Lα phases exist over wide composition ranges; certain additives induce transitions to other phases, which include cubic, reversed hexagonal liquid crystals and bicontinuous liquid phases. For a system containing additives, which induce a significant lowering of the Lβ–Lα transition, we identified the possibility of a triggered phase transition via dilution with water.

Oxidation-Induced Breakage of the Imine Bond and Aggregate Transition in a Se-Containing Dynamic Covalent Surfactant.

Controlling the dynamic imine bonds upon a novel trigger except for pH and temperature is still a significant challenge. Here, a Se-containing imine-based dynamic covalent surfactant (HOBAB-BSeEA) was developed for the first time by mixing two precursors in situ: an asymmetric double-chain cationic surfactant bearing a formyl group at the terminal of one hydrophobic tail and a Se-containing amine (2-(benzylselanyl)ethan-1-amine) in order to confirm the effect of redox on the imine bonds. The imine bond in HOBAB-BSeEA can be regulated not only upon changing the pH as well as other common imine-based surfactants but also by oxidation. The conversion efficiency of imine bonds is closely related with the degree of oxidation and pH. Complete oxidation can decrease the conversion efficiency from ∼87 to 48%, which is comparable to the result of changing the pH from 10.0 to 7.0. With the formation and breaking of imine bonds, the surfactant can be reversibly switched between symmetric and asymmetric structures, accompanied by a morphological transition from vesicles to spherical micelles. Although oxidation cannot demolish all imine bonds, it can completely convert vesicles to spherical micelles, which is mainly ascribed to an increase in the polarity of the micellar microenvironment stemming from the oxidation of Se. However, this transition can only be achieved by reducing the pH to 5.0 instead of 7.0. Nile red loaded in HOBAB-BSeEA vesicles can be quickly, controllably, and step-by-step released upon oxidation stimulus but not pH. Understanding the mechanism of oxidation-induced breakage of imine bonds and disruption of vesicles would be useful in designing redox-responsive imine-based carriers that can unload cargoes according to the level of the local reactive oxygen species.

Regulating Droplet Impact and Wetting Behaviors on Hydrophobic Weed Leaves by a Double-Chain Cationic Surfactant

The addition of a surfactant is a constructive strategy to enhance the deposition of pesticides on plant leaves in agriculture. However, currently used surfactants normally require to be used at high concentrations, and most of them are anionic or nonionic. In this work, we found that didecyldimethylammonium bromide (DDAB), a double-chain cationic surfactant, can not only inhibit droplets from receding and rebounding but also promote sufficient spreading on paraffin and Chenopodium album L. leaf surfaces at an ultralow concentration (0.05%), in comparison with widely reported sodium dodecyl sulfate (SDS) and bis(2-ethylhexyl)sulfosuccinate (AOT). This phenomenon is attributed to the fast adsorption kinetics of DDAB from the bulk to the newly created interface (mere 100 ms), decreasing the surface tension significantly. Field experiments further prove that the addition of DDAB can significantly improve the control efficiency of herbicides. Our findings provide a simple and effective way for improving the droplet deposition on hydrophobic plant surfaces, which may lead to economic and environmental benefits in the future.

Rayleigh and Rayleigh-Debye-Gans light scattering intensities and spetroturbidimetry of dispersions of unilamellar vesicles and multilamellar liposomes

Hypothesis: Since the volume fraction of the surfactant bilayer(s), of thickness db, in a vesicle and liposome is smaller than one, the dependences of the Rayleigh (R) scattering intensity and turbidity on the particle radius a are weaker than those for a homogeneous sphere, which are proportional to a3. The dependences of the Rayleigh-Debye-Gans (RDG) scattering intensity and turbidity on a are also weaker. Work done: The dependences of the effective relative refractive index on a, db, and dw (water layer thickness) were derived. The specific Rayleigh ratio Rθ** and the specific turbidity τ** for single and independent scattering were derived analytically for R and RDG scattering. Spectroturbidimetry data at 25°C for a cationic double-chain surfactant, didodecyldimethylammonium bromide (DDAB) were compared to the turbidity predictions. Findings: For R scattering, Rθ** and τ** are proportional to a2db for vesicles, and to a3dbdw+db for liposomes. For RDG and particle radii 20–1000 nm, τ** is proportional to an, where n is 2 to 0.4 for vesicles and 2 to 1.1 for liposomes. Turbidity data for DDAB vesicles are consistent with the RDG predictions, which are also used to estimate the vesicles’ sizes. RDG applies to liposomes < 800 nm and to much larger sizes for vesicles.

Phthalocyanine-modified surfactant-encapsulated polyoxometalate and its self-assembly in solution

Firstly, a novel functional double-chain cationic surfactant was designed and prepared in this study. Zinc phthalocyanine (ZnPc) was bonded onto the dodecyl (11-hydroxy-undecyl) dimethylammonium bromide (DHDA), obtaining the novel surfactant ZnPc-O-DHDA. Then, the surfactant-encapsulated polyoxometalate (POM) complex (ZnPc-O-DHDA/PW12) was prepared by using the double-phase co-precipitation method, through ion replacement with the Keggin-type polyoxometalate H3PW12O40 (PW12). The composition and structure of the complex were characterized using FT-IR, 1HNMR and elemental analysis (EA). ZnPc-O-DHDA has a good absorption and emission spectral performance in the visible region. When ZnPc-O-DHDA combined with PW12 to form a complex, and its Q-band fluorescence emission was enhanced because of the increased singlet–triplet energy gap of ZnPc. Thermogravimetric analysis (TGA) and EA data indicated the ratio of ZnPc-O-DHDA and PW12 in the complex was 2.8:1. ZnPc-O-DHDA/PW12 can self-assemble in DMSO/H2O (v:v = 4:1) solvent to form a spherical structure with a size of about 500 nm. The resulting aggregates could be successfully transferred into water to produce pellets of about 50 nm, while transferred into ethanol to produce small cubes of about 150 nm. The successful synthesis of this functional surfactant ZnPc-O-DHDA and its POM complex provide a new approach for the further design and preparation of functional POM aggregates.

Effect of a Cationic Surfactant on Droplet Wetting on Superhydrophobic Surfaces.

We experimentally and theoretically examine the influence of a double-chain cationic surfactant, didodecyldimethylammonium bromide (DDAB), on the wetting states and contact angles on superhydrophobic (SH) surfaces made of hydrophobic microcylinders. We use two types of micropatterns of different surface roughness, r, and packing fraction, ϕ, and vary nine dimensionless surfactant concentrations (CS), normalized by the critical micelle concentration (CMC), in the experiments. At low CS, some of the surfactant-laden droplets are in a gas-trapping, Cassie-Baxter (CB) state on the high-roughness microstructures. In contrast, some droplets are in a complete-wetting Wenzel (W) state on the low-roughness microtextures. We found that the contact angle of CB drops can be well predicted using a thermodynamic model considering surfactant adsorption at the liquid-vapor (LV) and solid-liquid (SL) interfaces. At high CS, however, all of the DDAB drops wet in a Wenzel mode. Based on a Gibbsian thermodynamic analysis, we find that for the two types of superhydrophobic surfaces used, the Wenzel state has the lowest thermodynamic energy and thus is more favorable theoretically. The CB state, however, is metastable at low CS due to a thermodynamic energy barrier. The metastable CB wetting state becomes more stable on the SH microtextures with greater ϕ and r, in agreement with our experimental observations. Finally, we generalize this surface-energy analysis to provide useful designs of surface parameters for a DDAB-laden surfactant droplet on the SH surface with a stable and robust CB state.

Effects of Light Dispersed Particles on the Stability of Dense Suspended Particles Against Sedimentation.

A novel method in which vesicular dispersions of the double-chain cationic surfactant DDAB (didodecyldimethylammonium bromide) stabilize suspensions of high density titania particles was recently presented (Yang, Y.-J; Corti, D.S.; Franses, E. I. Langmuir 2015, 31, 8802-8808). At high enough DDAB concentration, the vesicles form a close-packed structure, providing strong resistance to the sedimentation of the titania particles, while the dispersions remain highly shear-thinning with moderate limiting viscosities. Here, to elucidate the key factors of the mechanism by which vesicles or other nonsettling particles stabilize high density particles against sedimentation, we use Brownian dynamics simulations (BDS) to examine the sedimentation behavior of mixtures of "dense particles" that settle rapidly on their own and "light particles" that represent nonsettling "rigid vesicles". BDS confirm that for large enough values of the volume fraction ϕ2 of the light particles, the dense particles should remain suspended. The rheological behavior of the mixtures is also computed with BDS. The observed shear-thinning behavior of the light particle dispersion suggests that the suspensions of the dense particles are still flowable at high shear stresses. Furthermore, the local viscosity of light particles around the dense particles significantly increases with increasing ϕ2, particularly when the same gravitational force applied in the BDS is exerted on a dense particle. The arrangement of light particles around the moving dense particles is an important factor in determining the stability of the dense particles against sedimentation. The BDS results indicate that dispersions of nonsettling particles provide a general method for the stabilization against sedimentation of high density particles.

Micelle and Surface Tension of Double-Chain Cationic Surfactants.

Since the early 20th century, the slightly disparate measurements of a surfactant’s critical micelle concentration, via either surface tension or electrical conductivity, have been assumed one and the same. As a consequence, the possibility that micelles can adsorb at the air/water surface has been disregarded and has led to some abnormalities in the literature that remain as yet unresolved. In this paper, we closely examined the two critical concentrations for a double-chain cationic surfactant. We confirmed that the two concentrations represent two different physical phenomena. Furthermore, the results verified the existence of surface micelles, which are different from the bulk micelles. The formation of the surface micelles can be explained by the structural changes of the adsorption layer, which was also corroborated by molecular simulations. The findings open new challenges to examine the surface adsorption, which offers new insights into the molecular levels.

Mixed surfactant (altering chain length and head group) aggregates as an effective carrier for tuberculosis drug

Surface properties and aggregation behavior of cationic-cationic and cationic-non-ionic mixed surfactant systems viz. Dodecylethyldimethylammonium bromide (DDAB) with a series of double chain cationic surfactants (DiDDAB, DMDTAB, and DODAB) and non-ionic surfactants (Brij 96, Tyloxapol and Tween 80) were analysed using surface tension and transmission electron microscopy (TEM). The effect of chain length of cationic surfactant and hydrophilic-lypophilic balance (HLB) prominently observed in critical aggregation (cac) value. The aqueous solubility of anti-tuberculosis drug: rifampicin (RIF) was comparatively studied by UV–vis spectroscopy in presence of formulated micelles and vesicles. RIF was significantly solubilised in aqueous medium using all the formulated aggregates. RIF is very unstable in basic medium (above pH-7) and in oxidizing media. Therefore, stability at pH-13 as well as in strong oxidising environment was monitored using UV–vis spectroscopy. To trace the locus of the drug encapsulation in the micelles/vesicles, fluorescence spectroscopy and TEM studies were carried out. Both the techniques stemmed in complimentary results and confirmed that, RIF is majorly populated at polar medium in cationic-cationic vesicles and favour to reside at hydrophobic medium of the nonionic-cationic micelles.

Solvent Free Synthesis, Characterization and Evaluation of Dimethylaminopropylamine based Double Tailed Amidoamine Cationic Surfactant

Lauramidopropyl dimethylamine was quaternised using Lauryl Bromide to synthesize a double chain cationic surfactant. The surfactant was obtained in good yield without the use of any solvent. Amidoamine cationic surfactant chemical structure was analyzed using mass spectroscopic technique. The physicochemical properties of the amidoamine surfactant were calculated from surface tension and conductance measurements giving a critical micelle concentration of 8.04 × 10 -3 mM which is quite lower than conventional surfactants. The amidoamine also exhibits a good foaming ability and wettability. The amidoamine cationic surfactant was evaluated for efficacy against different microorganisms and the results show that it has good antimicrobial activity against both Gram positive and Gram negative bacteria.

Enhanced physical stability of positively charged catanionic vesicles: Role of cholesterol-adjusted molecular packing

Abstract A pseudodouble-chain ion pair amphiphile, hexadecyltrimethylammonium-dodecylsulfate (HTMA-DS), and a double-chain cationic surfactant, ditetradecyldimethylammonium bromide (DTDAB), were used as the main materials to form positively charged catanionic vesicles with various cholesterol contents. The effects of cholesterol on physical stability of the charged catanionic vesicles were then investigated by size, zeta potential, and Fourier transform infrared analyses. With the presence of cholesterol, the physical stability of the vesicles was enhanced. The inclusion of cholesterol would increase the distance between the charged headgroups of the vesicle-forming molecules and reduce the tendency of the counterion binding onto the charged vesicle surfaces, leading to a more pronounced charge character of the vesicles. Furthermore, with the incorporation of cholesterol, the sterol ring of cholesterol tended to maximize the contact with neighboring hydrocarbon chains, thus improving the bilayer mechanical strength. In the meantime, the alkyl side-chain of cholesterol together with the segments of the hydrocarbon chains near the ends in the vesicle-forming molecules could form flexible regions within the vesicular bilayers. Thus the presence of cholesterol in the bilayer structures of HTMA-DS/DTDAB catanionic vesicles not only enhanced the inter-vesicular electrostatic repulsion but also adjusted the intra-vesicular molecular packing, resulting in improved physical stability of the vesicles.

Phosphor-free silica-coating of monodisperse cores for dual functionalization with luminescent and mesoporous shell

To dually functionalize monodisperse cores with luminescence and mesopores, hydrolysis and condensation of tetraethyl orthosilicate in the presence of a double chain cationic surfactant of didodecyldimethylammonium bromide (DDAB) were applied to monodisperse silica cores with an average size smaller than 100 nm. Highly monodisperse core-shell particles were obtained by uniform coating of the cores with silica shell. Calcination of the silica shell at 500 °C to remove the incorporated DDAB surfactant provided the shells with mesoporous and luminescent properties without using any phosphors. The size of mesopores could be expanded by using dihexadecyldimethylammonium bromide (DHAB) with alkyl chains longer than DDAB. The combination of silica shell formation and calcination was also applied to monodisperse polymer cores, which created monodisperse, luminescent, hollow mesoporous silica particles (HMSs) with a sub-100 nm cavity inside. The emission intensity of mesoporous shell measured with an excitation wavelength of 365 nm could be sharply increased by an increase in the volume of mesoporous shell formed on the silica cores, implying that the luminescent centers derived from organic residue homogeneously distributed in the mesoporous shell.

A coacervative extraction based on single-chain and double-chain cationic surfactants

A coacervative extraction (CAE) with the common cationic surfactants dodecyltrimethylammonium bromide (DTAB) and didodecyldimethylammonium bromide (DDAB) was firstly developed. Notable characteristics of the CAE was the use of low concentration of salt (0.1molL−1 NaBr) at ambient temperature and without the requirement of organic solvent. The CAE was based on phase separation due to the neutralization of the surface charge of the micelle by electrostatic interaction with the predominant common counter ion (bromide). The coacervative phase was subjected to an optimized micellar liquid chromatography with UV (MLC-UV) method without any treatments. The method was applied to the determination of penicillins including amoxicillin, ampicillin, penicillin-G, oxacillin, and cloxacillin in milk samples. Method detection limits (MDLs) from standard were 0.5–2ngmL−1, and 40–80-fold analyte enrichment were obtained. The CAE-MLC-UV has shown to be of high potential for the analysis of five penicillins in milk with recoveries >90%.

A Microextraction Method Based on Ligandless Ion-Pair Formation for Measuring the Cadmium Cation in Real Samples by Flame Atomic Absorption Spectrometry

A new, simple, and ligandless ion-pair microextraction method has been developed for preconcentration and determination of cadmium ion in saline solutions and food samples. This technique is based on using a double chain cationic surfactant called didodecyldimethylammonium bromide (DDAB) as an ion-pairing agent and extraction solvent combined with dispersive microextraction named supramolecule aggregate-based dispersive liquid-solid microextraction (SA-DLSME) prior to aspiration to flame atomic absorption spectrometer. The Cd2+ ion interacts with chloride ion in saline solution, and the resulting anionic complex is microextracted by cationic supramolecule aggregates of DDAB due to electrostatic interaction. This technique benefits the advantages of supramolecule aggregate properties and dispersive liquid-liquid microextraction technique without the use of any dispersing solvent. Phase separation behavior of DDAB and several effective parameters that have influence on extraction efficiency of cadmium ion such as pH, salt concentration, centrifugation time, and DDAB amount were thoroughly investigated and optimized. Under the optimized experimental conditions, the limit of detection (LOD) and linear range were 1.3 and 5–250 ng mL−1, respectively, with relative standard deviations (RSD) in the range of 3.1–4.3 for interday analysis and 4.5–5.5 for intraday tests at different concentrations of cadmium. The proposed method was successfully applied for the determination of cadmium ion in real samples, and its accuracy was confirmed by analysis of a certified reference material.

Complex Behavior of Series of Cationic Carbamate Surfactants with SDBS, SDS, SAS Anionic Surfactants

Abstract The spontaneous formation of vesicles in aqueous catanionic mixtures, composed of six double-chain cationic surfactants 2,3-bis (alkyl carbamoyloxy)-N, N-dimethyl-N-(2-hydroxy alkyl) propyl chloride (CnPAC, n = 12, 14) and the three conventional anionic surfactants sodium dodecylbenzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), sodium dodecyl sulfonate (SAS), was investigated. The aggregation behavior of a catanionic system is proved by visual observation, electrical conductivity, dynamic light scattering (DLS), zeta (ζ) potential, and transmission electronic microscopy (TEM). By variation of the mixing ratios of cationic and anionic surfactants, we find that the formed vesicles are stable, and the complex system with hydrophobic C14 tail shows larger turbidity than that of hydrophobic C12 tail. The positive and negative electrostatic interactions are regarded as the main driving forces for vesicles formation.

Synthesis and Physicochemical Properties of Double-Chain Cationic Surfactants

In this study two types cationic surfactants were synthesized, purified, and characterized in our laboratory. One them is a series of cationic surfactants, a two tail–one head surfactant, N,N-dialkyl-N,N-diethylammonium bromide, abbreviated as “m-0-m” (m = 10, 12, and 16). The other type is N,N′-dialkyl-N,N,N′,N′-tetramethyl-N,N′-ethanediyl-diammonium dibromide, two tail–two head surfactants, abbreviated as “m-2-m” (m = 12 and 16). Once NMR spectra (1H NMR, 13C NMR) for all the gemini surfactants that were synthesized were taken, then the melting temperatures (TM) were measured. These surfactants have very high surface activity. The main goal of our study was to examine some properties of these two tail cationic surfactants by manipulating their dimeric structure. The effects of alkyl chain length and headgroup on surfactant self-assembly in solution were investigated. Critical micelle concentrations (CMC), degree of micelle ionization (α), and Krafft temperatures (TK) of 1 wt % aqueous solutions of these...

The influence of the micellar pseudophase of the double-chained cationic surfactant di-n-tetradecyldimethylammonium bromide on the absorption spectra and protolytic equilibrium of indicator dyes

Abstract The absorption spectra and protolytic equilibrium of a set of acid–base indicators and solvatochromic dyes have been studied in aqueous solutions of the cationic surfactants possessing two long hydrocarbon tails. In water, the double-chained surfactant di- n -tetradecyldimethylammonium bromide, DTDAB, forms large-sized anisometric self-assembled aggregates or bilayer (vesicle) type. The anionic dyes are readily bound to the DTDAB pseudophase, which results in the pronounced shifts of their absorption bands and alterations of the p K a s. The results have been compared with those obtained earlier in CTAB and gemini 16-4-16 cationic surfactants.

Enhancing physical stability of positively charged catanionic vesicles in the presence of calcium chloride via cholesterol-induced fluidic bilayer characteristic

An ion pair amphiphile (IPA), hexadecyltrimethylammonium-dodecylsulfate (HTMA-DS), and a double-chained cationic surfactant, dimethyldimyristylammonium bromide (DTDAB), could form positively charged catanionic vesicles with a potential application in gene delivery. To improve the gene delivery efficiency, the addition of CaCl2 into cationic liposomal systems has been proposed in the literature. In this study, detrimental effect of calcium chloride on the physical stability of the positively charged HTMA-DS/DTDAB catanionic vesicles was demonstrated by the size and zeta potential analyses of the vesicles. It was noted that the reduced electrostatic interaction between the catanionic vesicles could not fully explain the lowered physical stability of the vesicles in the presence of CaCl2. Apparently, the molecular packing/interaction in the vesicular bilayers played an important role in the vesicle physical stability. To modify the molecular packing/interaction in the vesicular bilayers, cholesterol was adopted as an additive to form catanionic vesicles with HTMA-DS/DTDAB. It was found that the physical stability of the catanionic vesicles was significantly improved with the presence of cholesterol in the vesicular bilayers even in the presence of 50 mM CaCl2. An infrared analysis suggested that with the incorporation of cholesterol into HTMA-DS/DTDAB vesicular bilayers, the alkyl chain motion was enhanced, and the molecular packing became less ordered. The cholesterol-induced fluidic bilayer characteristic allowed the vesicular bilayers to be adjusted to a stable status, resulting in improved physical stability of the catanionic vesicles even in the presence of CaCl2 with a high concentration.