Synthesis,Characterization, and Surface Properties of Cationic Gemini Surfactants

New pyridinium gemini surfactants have been synthesized by esterification of renewable fatty acids with mercaptoethanol furnishing respective esters (mercaptomethyl decanoate, mercaptomethyl dodecanoate, mercaptomethyl tetradecanoate, mercaptomethyl hexadecanoate) followed by their subsequent treatment with 4-dimethyl amino pyridine resulting in the formation of title gemini surfactants: 1-(5-(decanoyloxy)-2-hydroxypentyl)-4-((5-(decanoyloxy)-2-hydroxypentyl)dimethyl ammonio)pyridin-1-ium chloride (9), 1-(5-(dodecanoyloxy)-2-hydroxypentyl)-4-((5-(dodecanoyloxy)-2-hydroxypentyl)dimethyl ammonio)pyridin-1-ium chloride (10), 1-(5-(tetradecanoyloxy)-2-hydroxypentyl)-4-((5-(tetradecanoyloxy)-2-hydroxypentyl)dimethyl ammonio)pyridin-1-ium chloride (11), and 1-(5-(hexadecanoyloxy)-2-hydroxypentyl)-4-((5-(hexadecanoyloxy)-2-hydroxypentyl)dimethyl ammonio)pyridin-1-ium chloride (12). Their identifications are based on infrared, ¹H NMR, ¹³C NMR, distortionless enhanced polarization transfer, co-relational spectroscopy (COSY), and mass spectral studies. Their surface active properties are also evaluated on the basis of surface tension and conductivity measurements. Thermal stability of these long chain cationic gemini surfactants have been measured by thermal gravimetric analysis under nitrogen atmosphere.     

Adsorption and Corrosion Inhibition Behavior of L-Cystine and Synergistic Surfactants Additives on Mild Steel in 0.1 M H2SO4

The adsorption and corrosion inhibition behavior of mild steel in 0.1 M H₂SO₄ in presence of L-cystine and L-cystine in combination with surfactants sodium dodecyl sulfate and cetyltrimethyl ammonium bromide at 30–60°C was investigated using weight loss and potentiodynamic polarization measurements. Inhibition efficiency of L-cystine is synergistically enhanced on addition of surfactants. Surface morphology of corroded steel samples was evaluated using scanning electron microscopy and atomic force microscopy, which further confirmed the existence of an adsorbed protective film on the mild steel surface. Calculated thermodynamic parameters reveal that adsorption process is spontaneous and obey Langmuir adsorption isotherm.     

Synthesis of a Novel Class of Organosilicon Quaternary Ammonium Gemini Surfactants

A novel class of organosilicon quaternary gemini surfactants alkanediyl-α, ω-bis(methyl-dimethoxy-silopropyl-diethyl ammonium bromide) was synthesized with N,N-diethyl-aminopropyl-methyl-dimethoxysilane and α, ω-dibromoalkane as the raw materials, where the N,N-diethyl-aminopropyl-methyl-dimethoxysilane was synthesized by reacting diethylamine with γ-chloropropylmethyldimethoxysilane. The effects of various solvents on the conversion rate of the reaction and on purification of surfactants were investigated. The structures of the organosilicon quaternary ammonium gemini surfactants were determined by means of ¹H NMR and elemental analysis. The properties of aqueous solution were measured with electrical conductivity and viscosity methods.     

基于胱氨酸的Gemini型表面活性剂的合成及其性质

合成了基于胱氨酸的两种Gemini表面活性剂, N,N’-二对丁氧基肉桂酰胺基胱氨酸钠(SDBCC)和N,N’-二癸酰胺基胱氨酸钠(SDDC). 利用表面张力、动态光散射(DLS)、透射电镜(TEM)等手段研究了体系的表面性质和聚集行为.     

Industrial Applications of Dimeric Surfactants: A Review

Dimeric surfactants also known as gemini surfactants have received lots of attention for high performance formulations in the various scientific and commercial products. Due to the greater amount of hydrocarbon per molecule, the critical micelle concentrations (CMC) of dimeric are typically one order of magnitude lower than the corresponding monomeric surfactant. They are ten to hundred times more efficient at reducing the surface tension of water and the interfacial tension of the oil-water interface than conventional surfactants. Besides, the Krafft temperatures of gemini surfactants with hydrophilic spacers are generally very low giving these surfactants the capacity to be used in cold water. These surfactants display a range of interesting properties, including elevated surface activity, extremely low CMC and extraordinary rheology and self-assimilation aspect. As a consequence of these properties, they have many potential applications include detergents and cleaning agents, cosmetics, textile, and dyeing, dispersion stabilization and emulsion polymerization, genetics science, pharmaceutical, and biological applications.      

双子型阴离子表面活性剂的合成及浮选性能

分别以辛酰氯、癸酰氯、十二酰氯为原料,经加成、酰化及皂化等反应合成了3种双子型阴离子表面活性剂。产物结构经IR、1HNMR和13CNMR等波谱测试技术确定。25℃时测定了表面活性参数,结果表明随分子中疏水链增长,临界胶束浓度及表面张力均降低。目标化合物能一定程度增强油酸对胶磷矿中白云石的浮选能力。     

Interaction of Anionic Gemini Surfactants with Other Surfactants

The interaction of anionic gemini surfactants with other surfactants (such as anionic, cationic, nonionic) was systematically overviewed, paying attention to synergism observed in various properties. These mixed systems were found to show remarkable synergism in micelle formation. The critical micelle formation values being lower than the individual gemini surfactants indicate that the mixed micellization is due to attractive interaction between the two components. Almost all combinations were discussed in terms of respective surface tension reduction effectiveness and surface tension reduction efficiency and aggregation number for evaluation of synergism.     

Synthesis and Surface Properties of Novel N-Alkyl Quinoline-Based Cationic Gemini Surfactants

Two series of cationic dimeric (gemini) surfactants are prepared with respect to key surfactants properties, such as surface activity and solubilization. The influence of both the dimerization and the spacer group is examined in order to establish structure-property relationships. The surface tension and critical micelle concentration can be markedly reduced compared to the monomeric surfactants in the pure state. The critical micelle concentration (cmc) of each series has been determined using equilibrium surface tension measurements. Furthermore, air/water interface parameters including effectiveness (π_cmc), efficiency (P_C20), maximum surface excess (Γ _max ), and minimum surface area (A _min ) have been also derived using Gibb's adsorption equation at 25°C. Standard free energies of micellization and adsorption were calculated. Solubilization behaviors of the synthesized surfactants were measured towards paraffin oil as solubilized material using light transmission technique.     

Salt Effect,Surface, and Aggregation Properties of Binary Surfactant Mixtures of a Nonionic Gemini Surfactant (HBA(EO)80) with Anionic Surfactants

Nonionic gemini surfactants HBA(EO)₈₀ were synthesized and characterized by means of surface tension measurements. CMCs of two mixed system, nonionic gemini mixed with anionic gemini (HBA(EO)₈₀/C11pPHCNa) and nonionic gemini mixed with anionic monomeric (HBA(EO)₈₀/SL) and the effect of salt on the two mixed system were investigated. Freeze-fracture transmission electron microscopy and scanning electron microscopy were used to investigate the mixed aggregates' morphologies. The results show that large spherical aggregates were formed in the mixed solution, which trend to transfer into micelles with the increases of the salt concentration.     

Dynamic and molecular association in premicellar aqueous solutions of dicarboxylate amino acid-based surfactant as studied by 1H NMR

We examined a series of amino acid-based surfactants with two carboxylic groups separated by a spacer of one, two, or three carbon atoms with sodium and calcium counterions in the premicellar concentration region near the CMC. ¹H nuclear magnetic resonance (NMR) spectroscopy and NMR diffusometry techniques were used to study the local environment, association, and translational dynamics of the surfactant's molecules. We measured the self-diffusion coefficients of the micelles, calculated the effective hydrodynamic radii, and determined the temperature region in which the premicelles exist. With an increase in temperature from 295 to 335 K, the premicellar state of the surfactant is replaced by the monomeric state.     

Detection of Heavy Metal Ions Using Synthesized Amino Thiol Surfactants Assembled on Gold Nanoparticles

In this work, we synthesized amino thiol surfactants, namely, 10-(4-aminophenoxy)-decane-1-thiol and 12-(4-aminophenoxy)-dodecane-1-thiol. The self-assembling of the synthesized surfactants on gold nanoparticles (AuNPs) was investigated using different techniques such as ultraviolet analysis, x-ray diffraction, and transmission electron microscopy. The synthesized surfactants show the ability to assemble on gold nanoparticles and form stable nanostructure with it. We used the synthesized surfactants and their nanostructures with gold nanoparticles for the detection of Zn and Ni ions in aqueous solution using the ultraviolet spectrophotometer technique. The synthesized amino thiol surfactants showed the ability to detect Zn and Ni ions at low concentration. The results showed that gold nanoparticles can enhance the detection of Zn and Ni ions using the nanostructures of the synthesized surfactants.     

Study of the Interaction Between Promazine Hydrochloride and Surfactant (Conventional/Gemini) Mixtures at Different Temperatures

In the present paper, the micellization of an amphiphilic drug, promazine hydrochloride, and gemini surfactants (16-s-16) with s = 4–6 and the monomeric hexadecyltrimethylammonium bromide (CTAB) counterparts has been examined conductometrically in the pure and mixed states in aqueous solutions at different compositions and temperatures (298.15–308.15 K). Dicationic gemini surfactants provide much better environment for the micellization behavior than the corresponding monocationic counterpart CTAB. The critical micelle concentration (cmc) values are lower than the cmc for ideal mixing, cmc ^id, suggesting attractive interactions between the two components in mixed micelles. The micellar mole fractions of surfactants, evaluated by different models, show greater contributions of surfactants in mixed micelles and increase with increasing concentrations of these surfactants. The negative values of β suggest synergism in the mixtures, which is highly beneficial as it reduces the total amount of surfactants required in a particular application, leading to reductions of cost and environmental impact. Activity coefficients (f ₁ and f ₂) are always less than unity showing nonideality in the systems. The data have been also used for evaluation of thermodynamic parameters.     

Synthesis and aqueous solution properties of homologous gemini surfactants with different head groups

A series of homologous gemini surfactants possessing identical hydrophobic chains but different ionic head groups (cationic, anionic, zwitterionic) were synthesized, and their aqueous solution properties were examined. The results showed that the surface activities of gemini surfactants are superior to those of corresponding conventional monomeric surfactants, and molecular arrangements of gemini surfactants at the air-water interface are tighter than those of corresponding conventional surfactants. It was also found that zwitterionic gemini surfactant possesses the highest surface activity among the three surfactants. The behavior at the air-water interface is closely related to the molecular structural features of surfactants, which provide an indication for synthesizing highly-efficient surfactants.      

Interaction of Polyacrylamide with Conventional Anionic and Gemini Anionic Surfactants

The interaction of polyacrylamide (PAM) with conventional anionic (sodium lauryl sulphate, NaLS) and gemini anionic (sodium salt of bis(1-dodecenyl succinimic acid), represented as NaBDS) surfactants has been studied in alkaline medium by electrical conductance and surface-tension measurements at 35⁰C in order to compare the behavior of two surfactants toward the polymer. The surface parameters and thermodynamic parameters have been evaluated and compared. The results indicate more readily interaction of anionic gemini surfactant with the polymer (PAM).     

Oil Solubilization Capacity,Liquid Crystalline Properties,and Antibacterial Activity of Alkanolamine‐Based Novel Cationic Surfactants

A series of monomeric and dimeric cationic surfactants with tuned polarity was synthesized. Oil solubilization capacity, thermotropic liquid crystalline properties, and minimum inhibitory concentration (MIC) of novel hydroxylated cationic surfactants using selected gram positive and gram negative bacteria were examined. Antibacterial activity and the propensity of gemini surfactants for oil solubilization were observed to be better than those of corresponding monomeric surfactants. Pseudo ternary phase diagrams for these surfactants, methyl methacrylate (MMA), and water clearly showed, that microemulsions can be easily formulated with all these surfactants. Solubilization and foam studies of mixed surfactant systems were also examined. Molecular architecture like the tail length, head group area, and presence of ethanolic goups in the surfactant affect the performance properties. Unlike conventional gemini surfactants the synthesized gemini surfactants also show thermotropic liquid crystalline properties (smectic‐A, L_α phase).     

New anionic gemini surfactant based on EDTA accessible by convenient synthesis

A straightforward, broadly applicable synthetic strategy to anionic dimeric (“gemini”) surfactants is demonstrated, reacting ethylenediamine tetraacetic acid (EDTA) dianhydride with fatty amines. Characteristic surfactant properties in water are examined for the model compound based on N-methyldodecylamine. The new dimeric surfactant exhibits a low value for the critical micellization concentration (cmc < 10⁻⁴ mM), low surface tension at the cmc, and an enhanced solubilization capacity in comparison with a monomeric reference surfactant, sodium laurate. In particular, solutions of the gemini surfactant are remarkably stable in hard water, compared to conventional carboxylate surfactants.     

Micellization of monomeric and dimeric (gemini) surfactants in polar nonaqueous-water-mixed solvents

Dimeric or gemini surfactants are novel surfactants that are finding a great deal of discussion in the academic and industrial arena. They consist of two hydrophobic chains and two polar head groups covalently linked by a spacer. Data on critical micelle concentration (cmc) and degree of counterion dissociation (α) are reported on bis-cationic C₁₆H₃₃N⁺(CH₃)₂–(CH₂)_s–N⁺(CH₃)₂C₁₆H₃₃, 2Br⁻, referred to as 16-s-16, for spacer lengths s=4, 5, 6 in aqueous and in polar nonaqueous (1-propanol, 2-methoxyethanol or methyl cellosolve, dimethyl sulfoxide, acetonitrile)-water-mixed solvents. The behavior is compared with conventional monomeric surfactant cetyltrimethylammonium bromide (CTAB). Thermodynamic parameters are obtained from the temperature dependence of the cmc values. It is observed that micellization tendency of the surfactants decreases in the presence of polar nonaqueous solvents. However, detailed studies with dimethylsulfoxide (DMSO) show that the geminis nearly outclass the micellization-arresting property of this solvent. Also, within geminis, higher spacer length is found suitable for showing micellization even with high DMSO content (50% v/v). The implications of these results of gemini micellization may be useful in micellar catalysis in polar nonaqueous solvents.     

Using molecular dynamics simulations to identify the key factors responsible for chiral recognition by an amino acid-based molecular micelle

Molecular dynamics (MD) simulations were used to investigate the binding of six chiral compounds to the amino acid-based molecular micelle (MM) poly-(sodium undecyl-(L)-leucine-leucine) or poly(SULL). The MM investigated is used as a chiral selector in capillary electrophoresis. The project goal was to characterize the chiral recognition mechanism in these separations and to move toward predictive models to identify the best amino acid-based MM for a given separation. Poly(SULL) was found to contain six binding sites into which chiral compounds could insert. Four sites had similar sizes, shapes, and electrostatic properties. Enantiomers of alprenolol, propranolol, 1,1′-bi-2-naphthyl-2,2′-diyl hydrogen phosphate, 1,1′-bi-2-naphthol, chlorthalidone, or lorazepam were separately docked into each binding pocket and MD simulations with the resulting intermolecular complexes were performed. Solvent-accessible surface area calculations showed the compounds preferentially associated with binding sites where they penetrated into the MM core and shielded their non-polar atoms from solvent. Furthermore, with five of the six compounds the enantiomer with the most favorable free energy of MM association also experienced the most favorable intermolecular hydrogen bonding interactions with the MM. This result suggests that stereoselective intermolecular hydrogen bonds play an important role in chiral discrimination in separations using amino acid-based MMs.GRAPHICAL ABSTRACT     

Surface and Antimicrobial Properties of N-Palmitoyl Amino Acid–Based Surfactants

Synthesized sodium N-pamitoyl amino acids were evaluated for surface and antimicrobial properties and compared with sodium lauryl sulfate (SLS). Emulsion stability of the amino acid surfactants and calcium tolerance of the sodium N-palmitoyl isoleucine were better as compared to SLS. Wetting ability and foaming properties of the palmitic acid-based surfactants were inferior to SLS. N-Acyl amino acids exhibited better antibacterial activity compared to sodium salts of N-acyl amino acids and standard compounds against Staphylococcus aureus MLS-16 and Bacillus subtilis. These studies revealed that the palmitoyl amino acid surfactants can be exploited in household, skin care formulations, and industrial applications.