Synthesis and Properties of a New Piperazine-Based Bicaudate Gemini Surfactant

A novel bicaudate gemini surfactant was synthesized with anhydrous piperazine, chloride- bian, and 1-bromo dodecane as raw materials. Its structure was verified by infrared and ¹H NMR. The surface active properties of the bicaudate gemini surfactant in water were measured at 55°C. Its critical micelle concentration (cmc) and γ cmc was 0.50 mmol · L^?1 and 28.95 mN · m^?1, respectively. Results indicate that there was not a remarkable difference in γ_cmc values between the synthesized bicaudate surfactant and conventional gemini surfactant N,N′–bis (dodecyl dimethyl ammonium bromide)-3-oxa-1,5-pentadiammonium. The sterilizing antimicrobial performance of the bicaudate gemini surfactant was examined. The bicaudate gemini surfactant show excellent inhibition against 18 types of bacteria compared with conventional monomeric surfactant and gemini surfactant at concentrations of 50 mg/L.     

Interactions between β-cyclodextrin and an amino acid-based anionic gemini surfactant derived from cysteine

The interaction between β-cyclodextrin (β-CD) and an amino acid-based anionic gemini surfactant derived from cysteine (C₈Cys)₂ was studied by three independent techniques: electrical conductivity, UV–Vis spectral displacement technique using phenolphthalein as probe, and ¹H NMR spectroscopy. The data obtained indicated the formation of a 1:1 inclusion complex between β-CD and the gemini surfactant studied and allowed for the determination of the binding constant, K₁, by considering this stoichiometry. Electrical conductivity, spectral displacement technique, and NMR chemical shift measurements, obtained for aqueous β-CD–surfactant systems, yielded consistent K₁ values in the order of 10² dm³ mol^?1, typical of a weakly bound β-CD–surfactant complex. The influence of the presence of the inclusion complex on the micellization process of the gemini surfactant has also been studied and the apparent critical micelle concentration (cmc¹) has been obtained. Increasing β-CD concentration was found to shift the cmc¹ to higher values, as complexed surfactant monomers are not available to form micelles and aggregation takes place only when all β-CD cavities are occupied.     

Phase Behavior of n‐Butanol/n‐Octane/Water/Cationic Gemini Surfactant System

Phase diagrams of the n‐butanol/n‐octane/water/(12‐3‐12,2Br^?1) system were determined, where n‐octane usually represents oil (O), 12‐3‐12,2Br^?1 is a gemini cationic surfactant trimethylene‐1,3‐bis(dodecyldimethyl ammonium bromide) abbreviated as S, and n‐butanol is a co‐surfactant written as A. Effects of the weight ratio of gemini surfactant to cosurfactant, S/A, and of temperature on the phase behavior were studied. The microemulsion structures including O/W, bi‐continuous (B.C.), W/O, and liquid crystal were determined by the conductivity method and polarization measurement. Experimental results show that the gemini surfactant, used facilitates the formation of microemulsions compared with its corresponding monomeric surfactant, n‐dodecyl trimethylammonium bromide (DTAB). When S/A=1/1, and the total concentration of gemini surfactant and alcohol is 20–40%, microemulsions with higher water content can form in a wider region. When the temperature increases, the size and position of each type of microemulsion region changes notably.     

Micellization of anionic gemini surfactants and their interaction with polyacrylamide

A series of anionic gemini surfactants have been synthesized. The surface properties and micellization process of as-prepared sulfonate gemini surfactants (SGS) and carboxylate gemini surfactant (CGS) have been studied by surface tension measurement and isothermal titration microcalorimetry. Meanwhile, the interaction of these five surfactants with polyacrylamide (PAM) was investigated using surface tension, steady-state fluorescence measurement, and isothermal titration microcalorimetry. The results show that the critical micelle concentrations (CMCs) of above-mentioned surfactants are more than 1 order of magnitude lower than those of corresponding single chain surfactants. Moreover, the enthalpy of micelle formation (ΔH _mic) for the investigated gemini surfactants is negative. In the surfactant–PAM systems, the thermodynamic parameters of binding have also been determined. The conclusion may be drawn that the binding strength of SGS onto PAM is stronger than that of CGS, resulting from more compact structure of SGS aggregates. With increasing surfactant hydrophobicity, the values of ΔH _agg become more exothermic and a ΔS _agg decrease was observed. Therefore, the interaction between SGS and PAM is enthalpy-driven.     

Micellar effects of a triazole-based cationic gemini surfactant on the rate of a nucleophilic aromatic substitution reaction

The reaction between 2,4-dinitrochlorobenzene (DNCB) and hydroxide ion was studied spectrophotometrically at 25 °C in micelles of a triazole-based cationic gemini surfactant 18-triazole-18 or micelles of the conventional cationic surfactant CTAB. Both CTAB and 18-triazole-18 accelerated this nucleophilic aromatic substitution reaction. The binding constant of the substrate to the micelle, K _S, for 18-triazole-18 (K _S=335 M⁻¹) was found to be much larger than that for CTAB (85 M⁻¹) by fitting the kinetic results with pseudophase ion-exchange (PIE) model, which suggests that DNCB binds with gemini micelles more easily than it does with CTAB micelles. It was also found that 18-triazole-18 catalytic system was in accordance with PIE model at surfactant concentrations below ca. 0.5 mM, above which the increase of viscosity and the change of micelle size with increased surfactant concentration may remarkably influence the reaction. This was quite different from the reaction catalyzed by micelles of the conventional surfactant CTAB.     

Cleavable dicationic surfactant micellar system for the decomposition of organophosphorus compounds

A dimeric (gemini) surfactant containing cleavable ester groups has been synthesized and studied. The new surfactant has a low critical micelle concentration (2.7∙10^–5 mol/L) and Krafft temperature (≤0°C). Alkaline hydrolysis of 4-nitrophenyl diethyl phosphonate and 4-nitrophenyl diethyl phosphate in the presence of micelles of gemini surfactant I proceeds 30-144 times more rapidly than in water. Chemical cleavage of gemini surfactant I in an alkaline medium is achieved in 96 h.     

Synthesis and Antimicrobial Activity Studies of a New Twin-Tailed Gemini Surfactant Bearing Piperazine Heterocycle

A novel twin-tailed gemini surfactant was synthesized with anhydrous piperazine, 4-nitrobenzyl chloride and 1-bromo octane as raw materials. Its structure was verified by infrared and ¹H NMR. The optimum synthetic conditions were established by orthogonal array design. The sterilizing antimicrobial performance of the twin-tailed gemini surfactant was measured by using the disc diffusion method against 18 bacteria. The study indicated that the target twin-tailed gemini surfactant shows excellent inhibition against Pseudomonas aeruginosa, Bacillus thuringiensis, Sphaericus, Bacillus mucilginosus, and Penicillium chrysogenum compared with conventional gemini surfactant and dialkyl monomeric surfactant at the concentration of 10 mg/ml.     

两相催化体系中双子表面活性剂对1-十二烯氢甲酰化反应的助催化作用

合成了几种具有刚性连接基团的双子表面活性剂,研究了它们在Rh-TPPTS体系中催化长链烯烃氢甲酰化反应中的助催化作用.结果表明,在水/有机两相催化体系中,新型双子表面活性剂的助催化作用比单链表面活性剂CTAB更好,在较低的表面活性剂浓度下能得到较高的反应转化率.这归因于此类表面活性剂有较低的cmc,降低界面张力的能力和对1-十二烯的增溶能力比CTAB更强.     

Study on the Inhibition of Mild Steel Corrosion by Cationic Gemini Surfactant in 1 M HCl

The cationic gemini surfactant 1,2-bis(N-tetradecyl-N,N-dimethylammonium)ethane dibromide (14-2-14) was synthesized using a previously described method. The surfactant was characterized using ¹H NMR. The corrosion inhibition effect of 14-2-14 on mild steel in 1 M HCl at temperatures 30–60°C was studied using weight loss measurements, potentiodynamic polarization measurements and electrochemical impedance spectroscopy. Morphology of the corroded mild steel specimens was examined using scanning electron microscopy (SEM). The results of the studies show that gemini surfactant is an efficient inhibitor for mild steel corrosion in 1 M HCl; the maximum inhibition efficiency (IE) of 98.06% is observed at surfactant concentration of 100 ppm at 60°C. The %IE increases with the increasing inhibitor concentration and temperature. The adsorption of inhibitor on the mild steel surface obeys Langmuir adsorption isotherm. SEM studies confirmed smoother surface for inhibited mild steel specimen.     

Applications of cationic gemini surfactant in preparing multi-walled carbon nanotube contained nanofluids

Stable homogeneous nanofluids of multi-walled carbon nanotubes (MWNTs) were prepared by using gemini cationic surfactant trimethylene-1,3-bis (dodecyldimethyl ammonium bromide), abbreviated as 12-3-12,2Br⁻¹, as dispersing agents. Zeta potential and FT-IR measurements were employed to investigate the adsorption mechanism of 12-3-12,2Br⁻¹ on MWNTs. The interactions between MWNTs and 12-3-12,2Br⁻¹ through hydrophobic segments cause hydrophilic MWNT-suspended medium interfaces with high positive charges, which enables the nanofluids to be stable for long periods. At relatively low temperatures the superfluous surfactant molecules form stable layer or column micelles, making an increase in the viscosity of nanofluids. Only 0.6 wt% gemini surfactant was used to obtain 0.5 wt% MWNT dispersions. The dispersions show no MWNTs precipitation for at least 5 weeks.     

正离子Gemini表面活性剂/负离子聚电解质相互作用的研究

摘要 采用荧光探针法和电导法研究了正离子偶联表面活性剂(C₁₂H₂₅(CH₃)₂N-(CH₂)₆-N(CH₃)₂C₁₂H₂₅•2Br) (12-6-12• 2Br^－)和带相反电荷聚电解质聚丙烯酸钠(NaPA)的相互作用, 结果表明: 由于静电相互作用, 12-6-12•2Br^－和NaPA之间可以形成类胶束或复合物. 对比十二烷基三甲基溴化铵(DTMAB)与NaPA复配体系的荧光光谱, 发现偶联表面活性剂与NaPA的相互作用强于传统表面活性剂. 此外, 还研究了盐和醇对偶联表面活性剂/聚丙烯酸钠的复配体系微极性的影响, 发现盐和醇对表面活性剂在聚电解质上形成类胶束和复合物的溶解都有一定的促进作用.     

Supernucleophilic systems based on functionalized surfactants in the decomposition of 4-nitrophenyl esters derived from phosphorus and sulfur acids: II. Influence of the length of hydrophobic alkyl substituents on micellar effects of functionalized monomeric and dimeric imidazolium surfactants

New dimeric functionalized surfactants, 3,3′-[2-(hydroxyimino)propan-1,3-diyl]bis(1-alkyl-1H-imidazol-3-ium) dichlorides (Alk = C₁₂H₂₅, C₁₄H₂₉, C₁₆H₃₃), underlie the supernucleophilic microorganized systems capable of abnormally fast cleavage of acyl-containing substrates. Micellar effects both of monomeric and dimeric imidazolium surfactants in the cleavage processes of 4-nitrophenyl esters of diethylphosphonic, diethylphosphoric, and 4-toluenesulfonic acids are governed mostly by the hydrophobicity of the reaction components (acceleration ～10²–10³ times). The unquestionable advantage of dimeric surfactants is their especially low critical micelle concentrations (≤10^?5 mol L^?1), providing a possibility to attain the same micellar effects at the surfactant concentration lower by an order of magnitude (and yet even lower) than in the case of monomeric analogs.     

Effect of imidazolium-based ionic liquids on the aggregation behavior of twin-tailed cationic gemini surfactant in aqueous solution

Micellization behavior of the twin-tailed surfactants can be modulated by the addition of various modifiers. Ionic liquids (ILs) are one of them and are documented here. The beauty of these environmentally benign neoteric molecules lies in their structural versatility. Here, we have investigated the effect of three ILs: 1-butyl-3-methylimidazolium bromide ([C₄mim][Br]), 1-hexyl-3-methylimidazolium bromide ([C₆mim][Br]), and 1-octyl-3-methylimidazolium bromide ([C₈mim][Br]) on the aggregation and surface adsorption behavior of cationic gemini surfactant, bis(hexadecyldimethyl ammonium)propane dibromide (16-3-16) through experimentally measured electrical conductivities, surface tensions, and by spectral methods (UV-vis absorbance and fluorescence measurements). The main focus of the study is to observe the effect of added ILs on the critical micelle concentration (cmc), various surface parameters, aggregation number, and size of the aggregates of gemini surfactant. The results show that the more hydrophobic ILs, that is, [C₆mim][Br] and [C₈mim][Br] behave as electrolyte at lower concentration and cosurfactant at higher concentration, whereas moderately hydrophobic IL [C₄mim][Br] acts as an electrolyte at all concentration ranges studied. The modulating effects of ILs were also compared with conventional electrolyte (NaBr) at similar conditions.     

Micellar-catalyzed alkaline hydrolysis of 2,4-dinitrochlorobenzene in a cationic gemini surfactant

Micellar-catalyzed alkaline hydrolysis of 2,4-dinitrochlorobenzene (DNCB) in the presence of a conventional cationic surfactant CTAB or a cationic gemini surfactant 1,2-ethane bis(dimethyldodecylammonium bromide) (12-2-12) were studied spectrophotometrically at 25 °C. It was found that both CTAB and 12-2-12 micelles accelerated the alkaline hydrolysis of DNCB, and the binding constant of the substrate to the micelle, K_S, for 12-2-12 (K_S = 310 M⁻¹) was larger than that for CTAB (85 M⁻¹), which suggested that DNCB molecules bound with gemini micelles more easily than with CTAB. However, the second-order rate constant in micellar pseudophase (k_M = 1.22 × 10⁻³ s⁻¹) for 12-2-12 was lower than k_M for CTAB (4.01 × 10⁻³ s⁻¹) because the substrate may enter the interior of the 12-2-12 micelles. It was found also that 12-2-12 had a similar catalysis mechanism to CTAB when the concentration of 12-2-12 was relatively low (ca. <5 mM). However, above this concentration, higher microviscosity and significant increases in aggregation number and micelle size with increased surfactant concentration may remarkably influence the hydrolysis reaction.     

Role of added counterions in the micellar growth of bisquaternary ammonium halide surfactant (14-s-14): 1H NMR and viscometric studies

The change in the morphology of a series of dicationic gemini surfactants C(14)H(29)(CH(3))(2)N(+)-(CH(2))(s)-N(+)(CH(3))(2)C(14)H(29), 2Br(-) (14-s-14; s=4-6) on their interaction with inorganic (KBr, KNO(3), KSCN) and organic salts (NaBenz, NaSal) have been thoroughly investigated by means of (1)H NMR spectral analysis and the results are well supported by viscosity measurements. The presence of salt counterions results in structural transition (spherical to nonspherical) of gemini micelles in aqueous solution. With an increase in salt concentration all the three gemini surfactants showed changes in their aggregate morphology. This change is dependent on the nature and size of the added counterion. The effect of inorganic counterions on the micellar growth is observed to follow the Hofmeister series (Br(-) < NO(3)(-) < SCN(-)). The roles of organic counterions are discussed on the basis of probable solubilization sites of the substrate molecule in the gemini micelles, showing more growth in case of Sal(-) than Benz(-). The results are confirmed in terms of the obtained values of chemical shift (δ), line width at half height (lw), and relative viscosity (η(r)). Also, the growth of micelles was most pronounced for the gemini surfactant with the shortest spacer (s=4). This was attributed to the unique molecular structure of gemini surfactant micelles having flexible polymethylene spacer chain linking the twin polar headgroups.     

Polymerisation of styrene in microemulsion with catanionic surfactant mixtures

The use of aqueous catanionic surfactant mixtures in the oil-in-water (o/w) microemulsion polymerisation of styrene is reported. Catanionic surfactant mixtures of dodecyltrimethylammonium bromide 1 and sodium dodecylsulfate 3, or decanediyl-1,10-bis(dimethyldodecylammonium bromide) 2, a gemini surfactant, and the anionic surfactant 3 were used. Phase behaviour and polymerisation properties of the microemulsions were studied as a function of the total surfactant concentration and the cationic/anionic surfactant ratio. Single-phase o/w microemulsions were only formed if either the cationic or anionic surfactant were present in large excess. Upon -irradiation, polymer nanoparticles were obtained. Using dynamic light scattering, the particle radii were determined to be 10 to 20 nm, the size depending on the total surfactant concentration, the cationic/anionic surfactant ratio and the surfactant/styrene ratio. Size exclusion chromatography indicated molecular weights of polystyrene of between 3×10⁵ and 1.4×10⁶ Daltons. Catanionic 1/3 and 2/3 mixtures differ in their styrene solubilizations. In a 1- or 3-rich system, the solubilization efficiency can be improved by increasing the concentration of the oppositely charged minor surfactant component, while in a 2-rich system the addition of 3 only diminishes the efficiency. Possible reasons for the different behaviours are discussed.     

The Effect of a Cationic Gemini Surfactant,Ethonium, on the Physicochemical Properties of Quercetin in Solutions and on the Surface of Highly Dispersed Silica

The formation of supramolecular complexes with ethonium, a cationic gemini surfactant having a broad-spectrum antimicrobial activity, is shown to significantly alter the physicochemical properties (spectral, protolytic, and adsorption properties and solubility) of a natural f lavonol, quercetin. The constant of binding between quercetin and ethonium is calculated. Apparent dissociation constants pK _a1 ^a of quercetin in solutions of this cationic surfactant are for the first time determined within a broad concentration range. A shift in the pH dependence of quercetin adsorption by 0.5 units to the alkaline region upon the transition from a premicellar ethonium solution to a micellar one correlates with an increase in pK _a1 ^a under these conditions. The value of quercetin adsorption from aqueous ethonium solutions depends on the concentration of the cationic surfactant, pH of a solution, and the pK _a1 ^a value of the f lavonol bound into the supramolecular complex.     

Steady-state fluorescence investigations of aqueous binary mixtures of myristyl alcohol based bis-sulfosuccinate anionic gemini surfactant and effect of different conventional surfactants therein

The present research work is associated with the fluorescence investigations of binary aqueous mixed surfactants solutions of anionic bis-sulfosuccinate gemini surfactant (BSGSMA_1,8) and three different conventional surfactants—anionic viz. sodium dodecyl sulfate (SDS), cationic viz. cetyl trimethyl ammonium bromide (CTAB), and nonionic surfactant viz. Triton X 100. Steady-state fluorescence spectroscopy technique has been utilized to examine the micellization behavior of aqueous solution of pure myristyl alcohol-based BSGSMA_1,8 having flexible methylene chain [(CH₂)₈] as spacer group. Critical micelle concentration (CMC), aggregation number (N), and micropolarity of pure and mixed surfactants systems were explored during the investigations. The results revealed the best synergism behavior of prepared gemini BSGSMA_1,8 with SDS as compared to CTAB and Triton X 100. The maximum reduction in the value of pyrene intensity ratio (I₁/I₃) was observed for gemini and SDS mixed surfactant solution. On the other hand, the increased I₁/I₃ value of mixed gemini with Triton X 100 exhibited that mixed surfactant system of anionic gemini BSGSMA_1,8 with non-ionic Triton X 100 is not as compact as other mixed surfactant systems. Aggregation number increased and micropolarity decreased with increased concentration of gemini surfactants.     

Effects of Spacer Chain Length and Additives on Solution Properties of Cationic Gemini Surfactant

The critical micelle concentration (CMC) has been determined for the gemini surfactant trimethylene-1,3-bis(dodecyldimethyl ammonium bromide)12-s-12,2Br^?1 by means of electricity conductivity measurements. For the same number of carbon atoms in the hydrophobic chain per hydrophilic head group, geminis have CMC values well below those of conventional single-chain cationic surfactants. The CMC of 12-3-12 reduces with the addition of n-alcohol except ethanol and with the increase of n-alcohol chain length as well as increase of concentration of n-butanol and sodium chloride. Steady-state fluorescence quenching technology has been employed to study the aggregation number of micelle, which increases with increase in the length of n-alcohol. The Kraft temperature measurements also indicate that the stability of solid surfactant hydrate decreases along with the improvement of concentration of n-butanol and sodium chloride.     

Facile synthesis of gemini surface-active ATRP initiator and its use in soap-free AGET ATRP mini-emulsion polymerisation

A novel cationic gemini surfactant has been readily synthesised in 70 % total yield. The functional gemini surfactant can act both as an emulsifier and an atom transfer radical polymerisation (ATRP) initiator in mini-emulsion polymerisation of methyl methacrylate (MMA), in which no other emulsifier was required. 1-(Dimethylamino)dodecane (N,N-dimethyldodecylamine, DMDA) was found to be a good ligand in the activator generated by electron transfer (AGET) ATRP reaction. Kinetic studies indicated that the polymerisation featured controlled/living radical polymerisation.