Types Of Cationic Surfactants Research Articles

Drag reduction and degradation of nonionic surfactant solutions with organic acid in turbulent pipe flow

We investigated the drag reduction and degradation of nonionic surfactant (Aromox) solutions, which mainly consisted of oleyldimethylamine oxide (ODMAO) and had non-toxic and biodegradable properties, by measuring the pressure drop and flow rate in the circuit pipe flow system using a pump. It is revealed that the addition of a small amount of organic acids such as salicylic and cuminic acids to nonionic surfactant solutions noticeably improves mainly two kinds of drag-reducing abilities. The first is the increase in the critical Reynolds number at which the drag reduction ratio is the maximum, i.e., the drag reduction can be obtained at the larger Reynolds number. The second is the decrease in the level of degradation caused by the continuous circulation of surfactant solutions in the closed pipe system, so that the high level of the drag reduction keeps for a long time. Comparing with the mixture of typical cationic surfactant (Ethoquad O/12) which consists of the oleyl-bis-hydroxyethyl-methyl-ammonium chloride (OBHEMA) and sodium salicylate as a counterion in practical use, the mixture of nonionic solution and salicylic acid proposed in this study shows the comparable or better drag-reducing ability at the same concentration and temperature of surfactant solutions.

Removal of surfactant template from mesoporous titania

We have reported the synthesis of mesoporous titania with crystalline walls using hexadecyltrimethylammonium bromide (CTAB), a typical cationic surfactant, as a template and titanium sulfoxide as a reactant in aqueous solution (Shibata et al., 2005 [1]). In this study, the removal method of CTAB from the mesopores without calcination or collapsing the ordered porous structure is described. First, CTAB molecules in the pore were replaced by acetic acid molecules under moderate reaction conditions. FT-IR spectra confirmed the removal of CTAB and adsorption of acetic acid. Removal of the adsorbed acetic acid was then performed by addition of carbonate ions that desorbed the acetate ions on the surface of the mesoporous titania. Mesoporous titania after removal of CTAB by the present method was found to have a more uniform pore structure compared with that after removal of CTAB by calcination treatment.

An improved method for simultaneous square-wave voltammetric determination of amlodipine and enalapril at multi-walled carbon nanotubes paste electrode based on effect of cationic surfactant

A reproducible and sensitive analytical procedure has been developed for the simultaneous determination of amlodipine (AML) and enalapril (ENP) by square-wave voltammetry using a multi-walled carbon nanotubes paste electrode in the presence of cationic surfactant cetyltrimethylammonium bromide (CTAB). The experimental parameters, such as concentration and type of cationic surfactant, pH of Britton–Robinson (BR) buffer, and amount of carbon nanotubes in the paste were optimized. The anodic peak potentials of AML and ENP at multi-walled carbon nanotubes paste (MWCNTsP) electrode were found to be 0.790 and 1.21V [vs. Ag/AgCl (3.0molL−1 KCl)], respectively by square-wave voltammetry, whereas at a GCE was 0.753V for AML and no peak potential was observed for ENP. In addition, the surfactant has been found to influence the electrochemical determination by the way enhanced of better repeatability of analytical signals for AML and it was possible the simultaneous direct determination of AML and ENP on the MWCNTsP electrode, without pre-concentration of the antihypertensives into the working electrode before each determination. Under optimized conditions in Britton–Robinson buffer (pH 6.0) containing 10μmolL−1 CTAB, linear calibration curves were obtained in the range of 0.58–5.9μmolL−1 for AML and 2.0–57μmolL−1 for ENP, which shows adequate for the quantification in real samples. The limit of detection was 0.049 and 0.81μmolL−1, respectively, for AML and ENP. The proposed method was used to estimate the amounts of individual and simultaneous antihypertensives in pharmaceutical formulations. Statistical comparison between the results obtained by this method and those obtained by the chromatography method was carried out and no significant difference was observed.

Micellization and Catalytic Properties of Cationic Surfactants with Head Groups Functionalized with a Hydroxyalkyl Fragment

The catalytic activity of two homological series of cationic surfactants bearing a hydroxyalkyl fragment in the head groups R(CH3)2N+(CH2CH2OH)Br– and R(CH3)2N+(CH2CH2CH2OH)Br– toward the cleavage of the p-nitrophenyl esters of carbonic acids of different hydrophobicity (acetate, caprilate, caprinate, laurate, myristate) is shown to exceed that of typical cationic surfactants with the trimethylammonium (TMA) headgroup. The catalytic effect increases with the alkyl chain length of surfactants and nonmonotonous changes in the series: acetate < caprilate < myristate < laurate < caprinate, reaching 750 times. NMR and IR spectroscopy studies and the surface potential calculations revealed that the higher catalytic effect of hydroxyalkylated surfactants is not due to their higher surface potential and binding capacity toward substrates. This is in line with finding that binding constants for TMA series are higher than for their hydroxyalkylated analogues, which was demonstrated by the fitting of kinetic data in...

Effect of Temperature and Added Counter Ions on Micelle Formation of Guanidine Surfactants

Abstract Electrical conductivity was measured for aqueous solutions of long-chain guanidine surfactants (G12 and MG12) at different temperatures and with various added counter ions. The critical micelle concentration (cmc) of these surfactants determined from the specific conductivity (κ) vs. concentration (c) plot is lower than those of the typical cationic surfactants, such as alkyltrimethylammonium chloride with the same hydrocarbon chain length. The electrical conductivity data were analyzed according to the mixed electrolyte model of micelle solution, and the degree of counter ion binding (β) was calculated. The thermodynamic parameters for micelle formation were estimated using the values of cmc and β as a function of temperature. The more negative ΔGmic for MG12 indicates more favored micellization. The contribution of entropy term to the micelle formation is superior to that of enthalpy term in the system under study, which indicates micellization is entropy driven. By comparing the cmc and ΔGmic it is evident that all cmc decreases and the more observed negative ΔGmic in the presence of different added salts. The anion effect on the guanidine surfactants micelle formation with added salts showed the micelle forming efficiency order as: Cl− &lt; Br− &lt; NO3 − &lt; Ac−.

Cationic Micelles Modulated in the Presence of α,ω‐Alkanediols: A SANS, NMR and Conductometric Study

AbstractThe solution behavior of a typical cationic surfactant, tetradecyltrimethylammonium bromide, in mixed solvent systems composed of water and varying concentrations of α,ω‐alkanediols; 1,2‐ethanediol (ED), 1,4‐butanediol (BD), 1,6‐hexanediol (HD) and 1,8‐octanediol (OD) was examined via electrical conductance measurements, 13C‐NMR spectroscopy and small angle neutron scattering (SANS) measurements. The critical micelle concentration (CMC) values and degree of counterion dissociation (α) indicate that both ED and BD oppose micellization, whereas HD and OD enhance micelle formation. Changes in the 13C‐NMR chemical shifts (∆δ values) reveal that the short chain diols reside almost exclusively in the bulk phase and hence, affect the formation of micelles by altering the solvent properties in the bulk of the solution, whereas HD and OD partition between the pseudomicellar phase and the bulk phase. SANS studies indicated that both the micellar size and aggregation number (Nagg) decrease in the presence of all diols. ED and BD behave like cosolvents and increase the α and CMC values and decrease Nagg. We note that the effect of HD and OD on the properties of the micelles is concentration dependent; at low concentrations, these diols interact with the micelles and behave as cosurfactants (as evidenced by the trends in the micellar properties), while at higher concentrations, they enhance the surfactant solubility and behave as a cosolvent.

Application of Rheology for Energy Saving Air Conditioning System

Surfactant drag reduction is well known as the energy saving technology which is able to cause drastic reduction of pumping power during the fluid transportation. The combination of certain type of cationic surfactant with suitable counter ion is often chosen as the drag reduction agents. Power saving up to 70∼80% is available in straight pipe line system by using surfactant additives. Design problem, in particular, the scale up law in surfactant drag reduction system was solved by using the modified viscoelastic damping factor model along with the measurements of nonlinear viscoelastic properties of surfactant solution. Based on the prediction of the proposed model, it was demonstrated that the surfactant drag reduction technology is promising to construct the large scale energy saving system for air conditioning. Up to now, over 150 sites of building air conditioning had adopted the surfactant drag reduction in Japan, and the practical pumping energy reduction had been reported as 20∼50% compared with the case of no drag-reducing agent.

Investigation of gas/liquid interface of small bubbles formed in solutions of different alkylammonium chlorides

The electrophoretic mobility of nitrogen gas bubbles was measured in solutions of different n-alkylammonium chlorides in a cylindrical cell, 30 mm in diameter and 70 mm in length, rotating in order to keep the bubbles on a line of the rotation axis of the cylinder. An electric charge field was applied to the solutions through two electrodes located at both ends of the cylinder. The mobility was measured as a function of the size of bubbles. The maximum mobility U *(= v/ E) and the corresponding diameter of the bubble, d b * were used to determine the apparent surface charge density, σ at the gas/liquid interface. The surface charge density of bubbles was found (i) to be negative even in solutions of all n-alkylammonium chlorides carbon atoms, the number n of which was selected to be n = 1, 2, 3, and 10, and (ii) to decrease in magnitude with increasing number of carbon atoms. Decylammonium chloride (DAC; n = 10) is a typical cationic surfactant, however, the surface was revealed to still be negative, which strongly suggests that DAC molecules do not always come out to the gas/liquid interface. The change in surface charge density with the added salt concentration was analyzed, and as a result, it was found that only DAC follows the Langmuir adsorption isotherm.

Synthesis and evaluation of micellar properties and antimicrobial activities of imidazole‐based surfactants

AbstractThe synthesis of two types of imidazole‐based surfactants, [(ROCOCH2MIm)Br] and [(RNHCOCH2MIm)Br], of varying chain lengths (C10, C12 and C16), was conducted in the present work. The synthesis involves an initial reaction of bromoacetic acid with fatty alcohols or fatty amines, followed by quaternization with N‐methyl imidazole. The micellar properties of all the synthesized compounds were determined using surface tensiometry and compared with [(RMIm)Br], a well‐studied alkyl‐substituted imidazole‐based surfactant. Within the same homologous series, a decrease in critical micelle concentration (cmc) was observed with increasing alkyl chain length in all three types of cationic surfactants. Introduction of an ester [(ROCOCH2MIm)Br] or an amide group [(RNHCOCH2MIm)Br] in the alkyl chain lowers the cmc when compared to a cationic surfactant without functional group, [(RMIm)Br]. The synthesized surfactants were also assayed for antimicrobial activities and found to possess good activities against selected strains.

Electrical conductivity study on micelle formation of long-chain imidazolium ionic liquids in aqueous solution

Electrical conductivity was measured for aqueous solutions of long-chain imidazolium ionic liquids (IL), 1-alkyl-3-methylimidazolium bromides with C 12–C 16 alkyl chains. The break points appeared in specific conductivity ( κ) vs concentration ( c) plot indicates that the molecular aggregates, i.e., micelles, are formed in aqueous solutions of these IL species. The critical micelle concentration (cmc) determined from the κ vs c plot is somewhat lower than those for typical cationic surfactants, alkyltrimethylammonium bromides with the same hydrocarbon chain length. The electrical conductivity data were analyzed according to the mixed electrolyte model of micellar solution, and the aggregation number, n, and the degree of counter ion binding, β, were estimated. The n values of the present ILs are somewhat smaller than those reported for alkyltrimethylammonium bromides, which may be attributed to bulkiness of the cationic head group of the IL species. The thermodynamic parameters for micelle formation of the present ILs were estimated using the values of cmc and β as a function of temperature. The contribution of entropy term to the micelle formation is superior to that of enthalpy term below about 30 °C, and it becomes opposite at higher temperature. This coincides with the picture drawn for the micelle formation of conventional ionic surfactants.

Surface Adsorption and Micelle Formation of Surface Active Ionic Liquids in Aqueous Solution

Aqueous solutions of three kinds of surface active ionic liquids composed of the 1-alkyl-3-methylimidazolium cation have been investigated by means of surface tension and electrical conductivity measurements at room temperature (298 K). The surface tension measurements provided a series of parameters, including critical micelle concentration (cmc), surface tension at the cmc (gammacmc), adsorption efficiency (pC20), and effectiveness of surface tension reduction (Picmc). In addition, with application of the Gibbs adsorption isotherm, maximum surface excess concentration (Gammamax) and minimum surface area/molecule (Amin) at the air-water interface were estimated. The effect of sodium halides, NaCl, NaBr, and NaI, on the surface activity was also investigated. It was found that both the pC20 and the Picmc were rather larger than those reported for traditional ionic surfactants and the cmc values were somewhat lower than those for typical cationic surfactants, alkyltrimethylammonium bromides, and comparable to typical anionic surfactants, sodium alkyl sulfates. These results demonstrate that the surface activity of long-chained imidazolium IL is somewhat superior to that of conventional ionic surfactants.

Selective Precipitation of RNA, Supercoiled Plasmid DNA, and Open‐Circular Plasmid DNA with Different Cationic Surfactants

Precipitation of RNA and plasmid DNA in clarified lysate produced from a bacterial culture was studied using three cationic surfactants with a different number of alkyl groups in the hydrophobic tail and cationic head. All the precipitation mixtures contained 0.5 M of NaCl. The results obtained indicated that selective precipitation was achieved when different types of cationic surfactants were used. In this study, trimethyltetradecylammonium bromide (TTAB) appeared to be a promising precipitant for precipitation of supercoiled plasmid DNA.

DNA and cationic surfactants at solid surfaces

The behavior of DNA at different types of interfaces and how the formed structures DNA at an interface could be affected by cationic surfactant has been studied. Particular attention was paid to how the type of cationic surfactant and DNA (single or double stranded and length) affects the compaction/decompaction of DNA. Adsorption of DNA–cationic surfactant complexes is determined by a delicate balance of DNA–surface, cationic surfactant–surface, and cationic surfactant–DNA interactions. DNA do not adsorb on hydrophilic negatively charged surfaces due to effective electrostatic repulsion between DNA and the surfacs. However, the interaction between DNA cationic surfactant ions leads to a substantial adsorption of the formed DNA–cationic surfactant complex once the charge density of both the DNA macromolecule and the surface is sufficiently decreased. On hydrophobic surfaces, where both DNA and cationic surfactant interact with the surface, the presence of the cationic surfactant leads to a considerable increase in adsorbed amount and a significant layer compaction of DNA. The stability of the mixed adsorbed layer largely depends on the strength of the interactions between DNA and the cationic surfactant, as well as between the surface and the cationic surfactant. DNA interacts with small latex particles in a similar way as to the macroscopic hydrophobic flat surfaces.

Catalytic Hydrolyses of Carboxylic Acid Esters in the Presence of Gemini Surfactant

Hydrolyses of p‐nitrophenyl picolinate (PNPP) and p‐nitrophenyl acetate (PNPA) mediated by the micellar catalytic systems of two types of cationic surfactants [cetyltrimethylammonium bromide (CTAB), Gemini dimethylene‐1,2‐bis(cetyltrimethylammonium bromide) (16‐2‐16, 2Br−)] were investigated spectrophotometrically in the pH range of 7.0–9.0 and 25°C. Also, the effects of several kinds of additives, such as ethanol, cyclodextrins (CDs), on the hydrolytic reactions of PNPP and PNPA were studied systematically. It is noteworthy that: (1) double chain Gemini surfactant micellar system enhanced the hydrolyses of carboxylic acid esters notably compared with single chain surfactant (CTAB) micellar solutions under the same reaction conditions; (2) the apparent rate constants (k obsd) of PNPP and PNPA hydrolyses increased with the increasing in pH values of reaction media; (3) as additives, ethanol has effect on both PNPP and PNPA hydrolyses, and moreover, the k obsd for hydrolyses decreased with the increasing contents of ethanol (≤5%) at 25°C and pH 9.00; (4) the presence of CDs [α‐cyclodextrin (α‐CD), β‐cyclodextrin (β‐CD), γ‐cyclodextrin (γ‐CD)], as additives, showed different effects on PNPP and PNPA hydrolyses in different reaction systems.

Thermodynamics of Micellization and Adsorption of Three Alkyltrimethylammonium Bromides Using Isothermal Titration Calorimetry

Studies of the thermodynamic properties of micellization, as well as the enthalpy change of adsorption (displacement), were conducted using isothermal titration calorimetry (ITC). The cationic surfactants, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, and hexadecyltrimethylammonium bromide or cetyltrimethylammonium bromide were used. Adsorption studies were performed utilizing HiSil 233 precipitated silica as the substrate. The thermodynamics of micellization were studied at 28, 30, and 35 degrees C using ITC. DeltaHdil was calculated and graphed versus concentration in order to determine DeltaHmic and critical micelle concentration. From these data, DeltaGmic and DeltaSmic were also determined and found to be in agreement with values previously determined using traditional temperature-variation methods. The thermodynamics of adsorption were also determined at the above temperatures using ITC. Using the results, the heat of displacement, Qdisp, and enthalpy of displacement, DeltaHdisp, were calculated. A plot of DeltaHdisp as a function of concentration was generated and used to interpret the mechanism of adsorption in the four regions of a typical cationic surfactant adsorption isotherm.

Semicontinuous seeded cationic emulsion polymerization of styrene: The effects of the concentration and type of cationic surfactant

AbstractThe objective of this work was to analyze the effects of the concentration and type of cationic surfactant on the kinetic features (instantaneous and overall conversions) and colloidal characteristics [mean particle diameter, particle size distribution (PSD), and surface charge density] in the semicontinuous seeded cationic emulsion polymerization of styrene. 2,2′‐Azobis(N,N′‐dimethyleneisobutyramidine)dihydrochloride was used as an initiator. The surfactants were dodecyltrimethylammonium bromide (DTAB) and hexadecyltrimethylammonium bromide (HDTAB). So that the evolution of some polymeric and colloidal characteristics of the synthesized latices could be followed, the overall and instantaneous conversions were defined and determined gravimetrically. The PSDs and average particle diameters were determined by transmission electron microscopy and photon correlation spectroscopy. The surface charge density was determined by conductimetric titration. The evolution of the instantaneous conversions, the total number of particles, and the PSDs of the different reactions were related to the nucleation, growth, and coagulation processes taking place in the semicontinuous seeded emulsion polymerizations. The PSDs obtained from the reactions carried out with the emulsifier DTAB, at a concentration equal to its critical micelle concentration (cmc) and at a concentration twice its cmc, presented more and smaller particles than those obtained by the addition of HDTAB to the polymerization recipe. At lower emulsifier concentrations equal to half of the cmc, the system had lower colloidal stability with DTAB. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2322–2334, 2003

Intercalation of Polyfluorinated Surfactants into Clay Minerals and the Characterization of the Hybrid Compounds

Intercalation of seven types of cationic surfactants, including polyfluorinated surfactants, into a cation-exchangeable clay mineral, saponite, was investigated. All of the surfactants were found to intercalate in amounts exceeding the cation exchange capacity (CEC). This tendency was more evident in the cases of the polyfluorinated surfactants, ((((perfluoroalkanoyl)amino)ethyl)hexadecyl)dimethylammonium bromide (CnF-S, where n indicates the number of carbons in the perfluoroalkyl group, F denotes a fluorinated surfactant, and S denotes a surfactant having a single, long alkyl chain); C3F-S exhibited intercalation up to 4.4 times CEC as a saturated adsorption limit. The saponite interlayer distance increased upon surfactant intercalation and reached a constant value at intercalation levels exceeding CEC. The occupied areas for each surfactant molecule decreased in the order C1F-S > C2F-S > C3F-S among the polyfluorinated surfactants. All of the experimental results, including the saturated intercalation levels, the occupied areas, the interlayer distances, and the DSC measurements, suggest that CnF-S intercalated in saponite forms a rigidly packed bilayer structure in which the long alkyl chains tilt at an angle of ca. 35° with respect to the clay surface. The microscopic structure of the hybrid compounds is discussed.

Membranes based on polyelectrolyte–surfactant complexes for methanol separation

Polyelectrolyte–surfactant complex (PELSC) membranes were prepared by the interaction of the anionic groups of sodium cellulose sulfate (Na-CS) or sulfoethyl cellulose (SEC) with different types of cationic surfactants. The membrane properties were investigated using pervaporation (PV) experiments with different organic feed mixtures, containing methanol (MeOH) as a polar component. Methanol was mixed with cyclohexane, methyl- t-butyl ether (MTBE), and dimethylcarbonate (DMC). The results of the separation experiments employing the methanol-containing mixtures show that the membranes reveal both very high permselectivity and permeability even at moderate temperatures.

The interaction of isomeric hexanediols with sodium dodecyl sulfate and dodecyltrimethylammonium bromide micelles

The micelle formation process for a typical anionic surfactant, sodium dodecyl sulfate, and a typical cationic surfactant, dodecyltrimethylammonium bromide, has been investigated in a series of mixed solvents consisting of different concentrations of isomeric hexanediols (1,2-hexanediol and 1,6-hexanediol) in water. The critical micelle concentrations and the degrees of counterion dissociation of the mixed micelles were obtained from conductance experiments. Luminescence probing experiments have been used to determine the concentration of micelles in solution and, hence, the micellar aggregation numbers of the surfactants in the mixed solvent systems. The alcohol aggregation numbers were determined by combining the partition coefficients (obtained using NMR paramagnetic relaxation enhancement experiments) with the micellar concentrations from the luminescence probing experiments. All these results are interpreted in terms of the difference in the interaction of the isomeric hexanediols with the surfactant as a function of the position of the hydroxyl groups on the six-carbon chain of the alcohol.

Preparation and properties of a new type of carbohydrate‐based cationic surfactant

AbstractA new type of cationic surfactant, 6‐O‐monoesters of 3‐(trimethylammonio)propyl d‐glucopyranoside, was prepared in high yield by a simple chemoenzymatic synthesis. Surface‐active properties of the compounds were found to be highly dependent on the fatty acyl chain length in the 6‐O‐position with the dodecanoyl and tetradecanoyl esters exhibiting the highest ability to lower surface tension as well as having the lowest critical micelle concentration values. Furthermore, the dodecanoyl ester had excellent foaming properties. The new surfactants also showed antimicrobial activity. Thus, the most potent compound, the dodecanoyl ester, was able to inhibit growth of both bacterial (Gram‐positive as well as Gram‐negative) and fungal test strains. The antimicrobial effect was somewhat weaker compared to benzalkonium chloride, one of the most frequently used cationics for topical disinfection. However, compared to benzalkonium chloride, the new cationics exhibit a highly improved compatibility with anionic surfactants, as no precipitation took place even in highly concentrated solutions thereby providing a much more robust antimicrobial system. Finally, the new surfactants are expected to be readily biodegradable because they are carbohydrate ester‐based.