Cationic Surfactant Didodecyldimethylammonium Bromide Research Articles

The Reversible Transformation of a Vesicular Aggregate in Response to a pH Oscillation

The transformation of amphiphilic molecular assemblies in response to chemical oscillations is fundamental in biological systems. The reversible transformation of a vesicular aggregate (VA) in response to a pH oscillation is presented in this study. A VA composed of the cationic surfactant didodecyldimethylammonium bromide is transformed using a pH oscillation ranging between 3 and 7. When the VA attains a stable structure at extreme pH values, the transformation reaches the irreversible stage. However, the addition of a phosphate buffer to the VA suspension changes the pH oscillation pattern from being rectangular to triangular and decreases the oscillation amplitude, successfully achieving the reversible transformation of the VA. Maintaining the non-equilibrium (transient) structures throughout the transformation and not falling into the equilibrium state with a varying pH are essential for the reversible transformation. This may be common and essential for dynamics in biological cells.

Formation of gem-like dispersions of soft crystallites in water by vesicles of a cationic surfactant

A first discovery of iridescent liquid-like aqueous vesicle dispersions formed from the cationic surfactant didodecyldimethylammonium bromide (DDAB) is reported. Iridescence arises for some solid crystallites, thin films, and colloidal crystals, but has not yet been observed in systems that in effect remain liquid-like. Visual observations and spectroturbidimetry (ST) at wavelengths of 350–700 nm were used to determine vesicle sizes and microstructure formation in dispersions for DDAB weight fractions w between 0.020 and 0.030. The DDAB vesicle dispersions exhibited iridescent colors for w = 0.023–0.027, due to the formation of “soft” crystallites formed by self-assembled vesicles. Effective vesicle radii from 30 to 60 nm were inferred from the ST measurements. The volume fractions of the vesicles ϕv and their effective volume fractions ϕv*, which account for the electrostatic double layers around a vesicle, were also estimated. The high values of ϕv* for the iridescent dispersions indicate that they contain neighboring vesicles with highly overlapping electrostatic double layers, even though their values of ϕv remain relatively low. Hence, strong electrostatic repulsive interactions arise between the vesicles, which probably drive the formation of “soft” crystallites, and thus the observed iridescence. Nevertheless, these “soft” crystallites, which could be easily broken up but were quick to reform, remain suspended. Consequently, these vesicle dispersions still flowed as a bulk dispersion with a high viscosity; the dispersion as a whole remained liquid-like or as a “liquid gem”, in contrast to what occurs to the other colloidal crystals made of rigid colloids. Beside their beautiful appearances, these DDAB vesicle dispersions also act as effective stabilizers of dense silica suspensions against sedimentation even at relatively low values of w.

Synergistic solubilization of phenanthrene using micro-nanobubbles and cationic surfactants: Universal verifying, amplifying, and strengthening the synergy

Micro-nanobubbles (MNBs) with their negatively charged surface and cationic surfactant with a positively charged hydrophilic head were designed to synergistically solubilize polycyclic aromatic hydrocarbons (PAHs). Through response surface method experimentation, the results showed that MNBs had no obvious solubilizing effect for the PAH, phenanthrene. However, MNBs and the cationic surfactant didodecyldimethylammonium bromide (DDAB) had a synergistic solubilization effect on phenanthrene. Through the analysis of physical and chemical factors, it could be inferred that the synergy was caused by a conversion in the structure of the vesicles formed by DDAB after the combination of DDAB and MNBs. This structure conversion improved the phenanthrene solubility. In addition to being amplified, this synergy was verified to be universal and could be strengthened. The synergy, which increased with increasing DDAB and MNB concentrations, could achieve up to about 3 times the solubilizing as that without MNBs. In addition to DDAB, MNBs could also synergistically solubilize phenanthrene with other cationic surfactants. Changing the gas source of MNBs from air to nitrogen or oxygen could increase the negative surface charge, which enhanced the synergistic effect between MNBs and cationic surfactants. These results demonstrate a novel method for synergistic solubilization of PAHs by surfactant and MNBs while it can decrease the excessive use of surfactants causing the pollution issues. The synergistic effect between cationic surfactants and MNBs has the potential to be widely used in environmental and medical fields.

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.

Physicochemical evaluation of the effect of natural zeolite modification with didodecyldimethylammonium bromide on the adsorption of Bisphenol-A and Propranolol Hydrochloride

Wastewater pollution by organic anions is of great interest. Surfactant-modified zeolites exhibit high adsorption of both organic and inorganic toxicants. Here, bisphenol-A and propranolol hydrochloride were adsorbed on natural zeolite modified with the cationic surfactant didodecyldimethylammonium bromide with and without pretreatment of the zeolite with NaCl and HCl. Detailed physicochemical analysis shows chemisorption, electrostatic and hydrophobic interactions with the surfactant and bisphenol-A, and in the case of propranolol, also physisorption.

Influence of surfactants on a pre-adsorbed cationic layer: Removal and modification

Removal of organic species from solid surfaces is a crucial process. The use of oppositely charged surfactants provides a potential method for enhanced removal. Neutron reflectometry has been used to investigate the complex behaviour of a pre-adsorbed and tenacious layer of the cationic surfactant didodecyldimethylammonium bromide (DDAB) on a mica surface, during exposure to different organic species in solution. The anionic surfactant sodium dodecylsulfate (SDS) was shown to be able to remove the cationic layer, but only if anionic micelles were present in solution. To facilitate comparison with the behaviour of a non-ionic surfactant, the direct adsorption of pentaethylene glycol monododecyl ether (C12E5) to mica was also studied; low surface coverage adsorption was seen at the critical micelle concentration and above. C12E5 was then found not to remove the cationic layer, but did include into the layer to some degree. The presence of cationic surfactant on the mica was however shown to significantly modify the adsorption behaviour of the non-ionic surfactant.

Investigation on the adsorption mechanism and model of didodecyldimethylammonium bromide on ZnO nanoparticles at the oil/water interface

We systemically evaluated the effects of the additional ZnO nanoparticles (NPs) on the interfacial activity of the cationic surfactant didodecyldimethylammonium bromide (DDAB) with two hydrophobic chains by the interfacial tension (IFT) measurement and emulsification experiments. The addition of ZnO NPs greatly improved the interfacial activity of the mixed ZnO/DDAB system at the oil/water interface. The zeta potential and fluorescence spectra of the mixed ZnO/DDAB dispersions were investigated to explore the adsorption behavior of DDAB molecules on ZnO NP surfaces. The IFT between a homologous series of n-alkanes and DDAB aqueous solutions in the absence and presence of ZnO NPs was measured to explore the mechanism of the further IFT reduction caused by the additional ZnO NPs. The dynamic IFT data were fitted with two different models. The results indicated that the DDAB adsorption processes in the absence and presence of ZnO NPs were controlled by the mixed diffusion-kinetic controlled model.

Potential Hepatitis B Vaccine Formulation Prepared by Uniform-Sized Lipid Hybrid PLA Microparticles with Adsorbed Hepatitis B Surface Antigen.

For the purpose of strengthening the immunogenicity of the hepatitis B vaccine, which contains hepatitis B surface antigen (HBsAg), the development of biodegradable poly(lactic acid) (PLA) microparticles (MPs) modified with the cationic surfactant didodecyldimethylammonium bromide (DDAB) was attempted. DDAB-PLA MPs with an uniform size of about 1 μm were prepared in a simple and mild way. DDAB-PLA MPs with increased surface charge enhanced antigen adsorption capacity compared to plain PLA MPs. After immunization, DDAB-PLA MPs induced the gene expression of inflammatory cytokines and chemokines, which facilitated the following immune responses. DDAB-PLA MPs augmented the expression of co-stimulatory molecules along with the activation of bone-marrow-derived dendritic cells (BMDCs). DDAB-PLA MP-based vaccine formulations efficiently induced antibody production more than the aluminum-based vaccine and plain PLA MP-based formulation in vivo. Moreover, DDAB-PLA MPs were more likely to generate the polarization of the Th1 response indicating the cytotoxic ability against infectious pathogens. In conclusion, DDAB-PLA MPs could be a potent vaccine formulation to prime robust cellular and humoral immune responses.

Dry powder pulmonary delivery of cationic PGA-co-PDL nanoparticles with surface adsorbed model protein

Pulmonary delivery of macromolecules has been the focus of attention as an alternate route of delivery with benefits such as; large surface area, thin alveolar epithelium, rapid absorption and extensive vasculature. In this study, a model protein, bovine serum albumin (BSA) was adsorbed onto cationic PGA-co-PDL polymeric nanoparticles (NPs) prepared by a single emulsion solvent evaporation method using a cationic surfactant didodecyldimethylammonium bromide (DMAB) at 2% w/w (particle size: 128.64±06.01nm and zeta-potential: +42.32±02.70mV). The optimum cationic NPs were then surface adsorbed with BSA, NP:BSA (100:4) ratio yielded 10.01±1.19μg of BSA per mg of NPs. The BSA adsorbed NPs (5mg/ml) were then spray-dried in an aqueous suspension of L-leucine (7.5mg/ml, corresponding to a ratio of 1:1.5/NP:l-leu) using a Büchi-290 mini-spray dryer to produce nanocomposite microparticles (NCMPs) containing cationic NPs. The aerosol properties showed a fine particle fraction (FPF, dae<4.46μm) of 70.67±4.07% and mass median aerodynamic diameter (MMAD) of 2.80±0.21μm suggesting a deposition in the respiratory bronchiolar region of the lungs.The cell viability was 75.76±03.55% (A549 cell line) at 156.25μg/ml concentration after 24h exposure. SDS-PAGE and circular dichroism (CD) confirmed that the primary and secondary structure of the released BSA was maintained. Moreover, the released BSA showed 78.76±1.54% relative esterolytic activity compared to standard BSA.

Specular neutron reflection at the mica/water interface – irreversible adsorption of a cationic dichain surfactant

Neutron reflection from the important mineral mica at the solid/liquid interface is presented here using a new approach – a very thin mica crystal supported on a silicon substrate. This approach avoids the problems of crystal defects and surface undulations that have hindered previous work. The use of mica as a reflectivity substrate is important as it is a model surface, which is atomically smooth with a high structural charge. In this work the mica/water interface is fully characterized. In particular, a characteristic double critical edge is observed, arising from the higher scattering length densities of the mica and D2O subphase relative to the silicon support. The experimental data are modelled using a combined approach: conventional amplitude summation (matrix method) for the thin layers and reflected intensity summation with attenuation terms for the thick layers of mica and hydrocarbon adhesive. Reflection data from the adsorption of the dichain cationic surfactant didodecyldimethylammonium bromide (DDAB) to the surface of muscovite mica from aqueous solution are also presented. It is found that, at twice the critical micelle concentration, a bilayer of DDAB with a thickness of 24 Å is observed, containing essentially no water. Its partial removal by washing and ion exchange is also presented.

Aqueous solutions of the double chain cationic surfactants didodecyldimethylammonium bromide and ditetradecyldimethylammonium bromide with Pluronic F68: Dynamic surface tension measurements

The adsorption kinetics of mixtures of the non-ionic copolymer Pluronic F68 with two double chain cationic surfactants didodecyldimethylammonium bromide (di-DDAB) and ditetradecyldimethylammonium bromide (di-TDAB) is studied with dynamic surface tension experiments. A time dependent synergy is observed, in most of the mixtures. In a few cases, hindrance effects are observed. Clusters are formed at concentrations well below the critical micelle concentration (cmc), at the critical aggregation concentration (cac). The presence of the copolymer stabilizes the electrostatic repulsion between the positively charged quaternary ammonium headgroups of di-DDAB and di-TDAB. The electrostatic repulsion between the polar parts of the same and adjacent surfactant molecules is minimized. We compare our results with recently published results, using mixtures of these double chain cationic surfactants with hydroxypropylmethylcellulose.

Dynamic surface tension studies of mixtures of hydroxypropylmethylcellulose with the double chain cationic surfactants didodecyldimethylammonium bromide and ditetradecyldimethylammonium bromide

Dynamic and equilibrium surface tension experiments were carried out to study the adsorption kinetics of mixtures of the nonionic polymer hydroxypropylmethylcellulose (HPMC) with two double chain cationic surfactants, didodecyldimethylammonium bromide (di-DDAB) and ditetradecyldimethylammonium bromide (di-TDAB). Results are obtained concerning the capacity of the surfactants to lower surface tension, the rate of lowering, the extent of adsorption at the interface, the possibility of changing conformation during and after adsorption, and the interactions between the adsorbed molecules. A time-dependent synergy is observed in most of the mixtures, while in a few cases hindrance effects are observed. The interaction of HPMC with the double chain cationic surfactants resulted in complexes with higher surface activity than the two components alone. Two induction times were observed, the second ones being more significant in the presence of di-TDAB. At concentrations well below the critical micelle concentration (cmc), the critical aggregation concentrations (cac), evidence for clusters is observed.

Interactional and aggregation behavior of twin tail cationic surfactants with pluronic L64 in aqueous solution

The aqueous mixed systems of twin tail cationic surfactants didodecyldimethylammonium bromide, ditetradecyldimethylammonium bromide, and dihexadecyldimethylammonium bromide with pluronic L64 have been studied to determine the bulk aggregation and interactional behavior. Various experimental techniques, namely small-angle neutron scattering (SANS), fluorescence, conductivity, and surface tension, have been employed to investigate the mixed micellization. The SANS data analysis has been employed to determine the shapes of different aggregates formed. Pure twin tail cationic surfactants form vesicles whereas the micelles of pure pluronic L64 are spherical. The mixed systems (surfactant + L64) also form spherical micelles, and the spherical shape of mixed micelles is predominantly controlled by pluronic L64. Various interfacial parameters such as surface excess (Γ max), minimum area per molecule (A min), and thermodynamic parameters such as the standard Gibbs free energy of micellization (\( \Delta G_{{mic}}^{{0}} \)), Gibbs free energy of adsorption (\( \Delta G_{{ads}}^{{0}} \)), and effective Gibbs free energy (\( \Delta G_{{eff}}^{{0}} \)) have been determined from the surface tension measurements. The results were interpreted on the basis of pseudophase separation model and regular solution theory. The interactions of each surfactant with pluronic L64 are found to be nonideal and antagonistic. The repulsive nature of the interaction is explained on the basis of the changes in the microenvironment of micelles of pluronic L64. Micelles of pluronic L64 are less hydrophobic and contains significant amount of water, and inclusion of hydrophobic alkyl chains of twin tail cationic surfactants disturbs this microenvironment of pluronic L64 micelle.

Synergistic effects in mixtures of two identically charged ionic surfactants with different critical micelle concentrations

Expressions for the critical micelle concentration (cmc) and activity coefficients as functions of surfactant composition in mixtures of two identically charged monovalent ionic surfactants are derived from the nonlinear Poisson–Boltzmann (PB) theory. For the special case of no added salt, the simple expression cmcα = xcmcα1 + (1 − x)cmcα2 is deduced, where the exponential parameter α > 1 depends on the number of ionic species in a surfactant molecule as well as the curvature of the self-assembled interface. Theoretical predictions are compared with cmc values obtained with some different experimental techniques for mixtures of the two cationic surfactants didodecyldimethylammonium bromide (DDAB) and dodecyltrimethylammonium bromide (DTAB) in water and in the absence of added salt. It is demonstrated that the PB theory generates significantly better agreement with experimental data than predicted by ideal behaviour or the regular mixture theory. We find that maximum synergistic effects occur at a DDAB mole fraction in solution y = 0.005. According to the PB theory, this very low value of y corresponds to a mole fraction of DDAB in the self-assembled interfacial aggregates equal to x = 0.995. Moreover, our calculations of the surfactant composition in the self-assembled interfacial aggregates above cmc demonstrate that the transition from small micelles to large bilayer aggregates is found to consistently occur at a mole fraction of DDAB equal to about x = 0.41–0.42, irrespective of the surfactant molar ratio in solution. Experimental observations strongly support the fact that concentrations of free surfactant, as well as the surfactant composition in the self-assembled interfacial aggregates, may be accurately calculated from the non-linear Poison–Boltzmann theory. On the other hand, a micelle-to-bilayer transition induced by changes in surfactant mole fraction in the self-assembled interfacial aggregates is consistent with neither ideal surfactant behaviour nor synergistic behaviour according to the regular mixture theory.

One-pot synthesis of monodispersed ZnS nanospheres with high antibacterial activity

A facile one-pot method to prepare water-soluble, uniform-sized ZnS nanospheres (NSs) is reported. In the reaction, gradually decomposed thioacetamide (TAA) was used as the sulfur precursor, and cationic surfactant didodecyldimethylammonium bromide (DDAB) embedded with ferrocene (Fc) as the ligands for anions. The synthesized ZnS NSs were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). Wonderfully, the obtained ZnS NSs exhibited high performance in prohibiting the growth of Escherichia coli strain MG1655 (E. coli) and negligible mammalian cell toxicity, and these important features make it a promising antimicrobial agent for controlling implant-related infections.

Surfactant bilayer coatings in narrow-bore capillaries in capillary electrophoresis

The cationic surfactants didodecyldimethylammonium bromide (DDAB) and dioctadecyldimethyl-ammonium bromide (DODAB) have previously been shown to form semi-permanent coatings that effectively prevent adsorption of cationic proteins in fused silica capillaries with inner diameters of 25-75 µm. This paper investigates the impact that narrower capillary diameters (≤25 µm) have on the stability of surfactant bilayer coatings and the efficiency of separations of model cationic proteins and neurotransmitters. Using a DODAB-coated 5 µm i.d. capillary 210 consecutive protein separations (1050 min) were performed without recoating the capillary between runs. Separation efficiencies of 1,400,000-2,000,000 plates per m (340,000-430,000 plates) were obtained. Migration time reproducibilites of 6.8% RSD were observed for 300 injections performed over a 30 day period without any regeneration of the coating. Neurotransmitters were separated with efficiencies ranging from 470,000-610,000 plates per m (110,000-140,000 plates) in a 5 µm capillary.

Electrochemistry of Sc3N@C78 embedded in didodecyldimethylammonium bromide films in aqueous solution

The electrochemical behavior of trimetallic nitride clusterfullerene (Sc3N@C78) embedded in films of the cationic surfactant didodecyldimethylammonium bromide (DDAB) on glassy carbon (GC) electrodes in aqueous solution was investigated. Four pairs of reversible redox peaks were observed in the potential range between +0.6 and −0.9 V vs. SCE. Different to the electrochemistry of pristine Sc3N@C78 in organic solution, the first reduction is a one-electron rather than simultaneous two-electron process because of the strong binding between DDA+ and the monoanion of Sc3N@C78. The generated radial monoanion, dianion and trianion of Sc3N@C78 are stable during continuous potential cycling, while some chemical reactions take place when the third anion is further reduced in the films. The cyclic voltammograms of Sc3N@C78/DDAB films checked at different temperatures pointed to strong temperature dependence. The electrochemical processes were also measured in different electrolytes, which showed pronounced anionic dependence and no cathodic dependence on either the cation or anions present. A possible electron-transfer mechanism of a Sc3N@C78/DDAB film was presented.

Cationic double-chained surfactant as pseudostationary phase in micellar electrokinetic capillary chromatography for drug separations

The cationic double-chained surfactant didodecyldimethylammonium bromide (DDAB) was used as pseudostationary phase (PSP) in micellar electrokinetic capillary chromatography (MEKC). Its performance on the three kinds of drugs, i.e., basic, acidic, and neutral drugs, was systematically investigated. Nicotine, cotinine, caffeine, lidocaine, and procaine were selected as the model basic drugs. Good baseline separation and high efficiency were obtained under the optimal separation condition that consisted of 50 mM phosphate (pH 4.0) and 0.08 mM DDAB. Three basic phenylenediamine isomers can also be well separated with DDAB in buffer. In addition, DDAB can form cationic bilayer on the capillary wall, thus the wall adsorption of basic analytes was greatly suppressed. Compared with commonly used CTAB, the separation of basic drugs was significantly improved with a much lower amount of DDAB present in the buffer. The DDAB-involved MEKC also showed superiority to CTAB upon the separation of acidic drugs, amoxicillin and ampicillin. In the case of neutral compounds, a good separation of resorcinol, 1-naphthol and 2-naphthol was achieved with 0.1 mM DDAB and 30% (v/v) acetonitrile (ACN) present in buffer. Hence, it was concluded that the double-chained cationic surfactant DDAB can be a good substitute for traditional single-chained surfactant CTAB in MEKC.

Assessment of the surfactant-dye binding degree method as an alternative to the methylene blue method for the determination of anionic surfactants in aqueous environmental samples

The surfactant to dye binding degree (SDBD) method is proposed for the routine monitoring of anionic surfactants in aqueous environmental samples and their analytical features compared with those provided by the standard methylene blue (MB) method. This new analytical approach is based on the effect that anionic surfactants exert on the binding degree of the cationic surfactant didodecyldimethylammonium bromide (DDABr) to the anionic dye Coomassie Brilliant Blue G (CBBG). The formation of DDABr-CBBG aggregates is monitored photometrically. The analytical applicability of the proposed method was demonstrated by determining anionic surfactants in tap, river and swamp water, and raw and treated sewage. The mean recoveries obtained ranged between 99 and 101%. The SDBD method offers important advantages over the classical MB method: it is more sensitive, selective, precise, simple and rapid; the analytical response is independent of the molecular structure of the anionic surfactants, and the volume of sample required for analysis and the consumption of organic solvents are significantly reduced.