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Abstract: Trimeric surfactant modified montmorillonite immobilized in alginate beads (CA/3RenQ-Mt) sorbent was synthesized to simultaneously remove Cu2+ and methyl orange (MO) from aqueous solution. The CA/3RenQ-Mt was characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TG), zeta potential analysis and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) analysis. The adsorption of Cu2+ and MO by CA/3RenQ-Mt was studied by the operational variables including contact time, pH and temperature. The results showed CA/3RenQ-Mt exhibited higher affinity to both Cu2+ and MO compared to sodium montmorillonite (Mt-Na), trimeric surfactant modified montmorillonite (3RenQ-Mt) or calcium alginate (CA). The pseudo-first-order kinetic model and Langmuir isotherm model were found to describe the MO adsorption well; the pseudo-second-order kinetic model and Freundlich isotherm model fitted well with the Cu2+ adsorption. The adsorption of MO onto CA/3RenQ-Mt is an endothermic spontaneous process, and ion-exchange was the dominant adsorption mechanism. Accordingly, the adsorption of Cu2+ on CA/3RenQ-Mt involved endothermic spontaneous chemical adsorption by means of coordination/chelation between Cu2+ and the oxygen atoms of carboxyl and hydroxyl groups of alginate. In general, CA/3RenQ-Mt can be applied as multifunctional adsorbent to remove heavy ions and anion dyes from aqueous solution. [ABSTRACT FROM AUTHOR]

Abstract: In recent years, trimeric surfactants have created excitement in the surfactant field because of their properties, which have been found to be better than monomeric or dimeric homologues. Only a limited number of trimeric surfactants have been synthesized and studied so far, probably owing to the difficulty in synthesis. In this article, we synthesized some novel star‐shaped trimeric cationic surfactants based on the alkylation of the 3 hydroxyl groups of the phloroglucinol nuclei as a core (i.e., spacer) with 3 dodecyl or 3 octyl groups (as tails) for the surfactant. The chemical structures were confirmed by nuclear magnetic resonance, Fourier transform infrared, mass spectrometry, and elemental analysis; also the critical micelle concentration was determined by electrical conductivity measurements. These surfactants were used in the synthesis of mesoporous silica nanoparticles by the sol–gel method. The silica particles shape and size were determined using field emission scanning electron microscopy and high‐resolution transmission electron microscopy images. Furthermore, the corrosion inhibitor capability of these surfactants was investigated by monitoring the corrosion rate of iron sheets in 0.5 M hydrochloric acid in the presence and in the absence of different surfactants at 45°C based on the weight loss method. We have used cetyltrimethylammonium bromide (CTAB) as a positive control, the obtained results showed a high inhibition efficiency at very low concentrations, and the prepared trimeric surfactants exhibited a higher anticorrosion efficiency than the CTAB surfactants. [ABSTRACT FROM AUTHOR]

Novel trimeric surfactants consisting of three units of sodium N-acyl-L-cysteine linked with hexahydro-1,3,5-triazine as the central core ((CnCy)3Na3, where n represented alkyl chain carbon number of 8, 10, and 12) were synthesized. Their conjugated acids were analyzed using FTIR, NMR, and ESI-MS to elucidate their chemical structures. The surface activity properties of (CnCy)3Na3were determined using surface tension and electrical conductivity measurements. It was found that (C12Cy)3Na3had a critical aggregation concentration (CAC) two orders of magnitude lower than that of the corresponding monomeric surfactant sodium N-lauroyl-L-cysteine (C12CyNa). The value of the minimum surface area per molecule (Amin) of (C12Cy)3Na3was almost three times greater than that of C12CyNa due to the increase in the degree of oligomerization. With the alkyl chain length increasing from 8 to 12, the CAC values decreased, and the values of the surface tension at CAC (γCAC) and the efficiency of the surface adsorption (pC20) increased. Furthermore, dynamic light scattering (DLS) and transmission electron microscopy (TEM) were used to evaluate the size and morphology of the aggregates at 10CAC. The results indicate that (CnCy)3Na3can spontaneously self-assemble into spherical or ellipsoid aggregates, and the surfactants with longer chain length can form larger aggregates due to greater hydrophobic interactions. [ABSTRACT FROM AUTHOR]

The dynamic surface tensions of gemini surfactants with spacers containing cyclic structures such as diethylene and triethylene chains, and atoms such as oxygen and nitrogen, and of linear- and star-type trimeric surfactants with spacers having propylene or hexylene chains between the quaternary ammonium groups (for the linear-type) and propylene or hexylene chains between the quaternary ammonium group and the central amino group (for the star-type) were measured using the maximum bubble pressure method. The effects of the molecular structures and surfactant concentration on the maximum rate of reduction in the surface tension as well as the diffusion coefficient were elucidated. The gemini surfactants containing cyclic structures in the spacer exhibited slower interfacial adsorption, which was ascribed to their rigid spacer structure. The longer the spacer chain length of the gemini surfactants, the greater the molecular flexibility and hence the faster the adsorption at the interface. Thus, the diffusion and adsorption of gemini surfactants are affected by the rigidity and hydrophobicity of the spacer, respectively. However, the adsorption of the trimeric surfactants at the air/water interface (which resulted in a maximum rate of reduction in the surface tension of 0.0007–0.004 mN m–1 s–1) was lower than that of the gemini surfactants (which resulted in a maximum rate of reduction in the surface tension of 0.0009–0.9 mN m–1 s–1). This was ascribed to the greater bulkiness of trimeric structures compared with those of the gemini surfactants. The star-type trimeric surfactants adsorbed faster at the air/water interface than the linear-type trimeric surfactants because the former were flexible despite their bulky spacer structure. For the linear- and star-type trimeric structures, the diffusion rate increased with the spacer chain length because of the resulting increase in the molecular flexibility. The linear-type surfactants were adsorbed faster at the air/water interface as their spacer chain length was increased, whereas the star-type surfactants were adsorbed more slowly because of their molecular bulkiness. [Display omitted] • Adsorption dynamics of gemini and trimeric surfactants at air/water interface are studied. • Gemini surfactants are adsorbed faster at the air/water interface than trimeric surfactants. • Star-type trimeric surfactants show faster adsorption than linear-type trimeric surfactants. • Their adsorption rates are especially influenced by the flexibility of molecular structure. [ABSTRACT FROM AUTHOR]

Series of quaternary ammonium-based gemini surfactants with long alkyl chains (C12 and C18) containing different spacers and substituents attached to the polar head group have been synthesized and their aggregation properties in aqueous solution examined. The effect of the hydrophobic chain, the nature and structure of the spacer group and the polarity of the head group on the aggregation behavior of such dimeric surfactants has been investigated. The critical micelle concentration (cmc) values of gemini surfactants in aqueous solution were determined by conductivity, steady state fluorescence and potentiometric measurements. The size of aggregates formed by investigated amphiphiles above the cmc in aqueous solution was examined by dynamic light scattering. Gemini surfactants show cmc values significantly lower than those of comparable single chain surfactants. The tendency of trimeric surfactants with a rigid spacer to form aggregates is higher than that of the corresponding dimeric surfactants. As occurs for monomeric ionic surfactants, the cmc of gemini surfactants decreases with the elongation of the hydrophobic chain. However, the effect of lengthening the alkyl chain on the cmc depends on the structure of the spacer. C12 gemini surfactants with a rigid hydrophobic spacer exhibit cmc higher than those containing a flexible hydrophobic spacer. For gemini surfactants with C18 alkyl chains this effect is even more pronounced and leads to differences in cmc values greater than one order of magnitude. The structure of the spacer, flexible or rigid chain, has been found to be a critical parameter on the self-assembly of long chain gemini surfactants. Spherical micelles are spontaneously formed above the cmc for C12 gemini surfactants, whereas trimeric and C18 gemini surfactants seems to form vesicle-like aggregates when self-aggregation occurs. [ABSTRACT FROM AUTHOR]

Trimeric surfactant methyldodecylbis [2-(dimethyldodecylammonio)ethyl] ammonium tribromide (3RenQ) and the corresponding dimer 1.2-bis(dodecyldimethylammonio)ethane dibromide (2RenQ), were used to modify sodium montmorillonite. Organo-montmorillonites 3RenQ-Mt and 2RenQ-Mt were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, N 2 adsorption isotherms, thermogravimetric analysis (TG), scanning electron microscopy (SEM) and dispersibility measurement. The results showed that 3RenQ and 2RenQ had inserted into the lamella of sodium montmorillonite successfully, the interlayer spacer and the hydrophilicity of organoclays increased with the increasing of the cationic exchange capacity (CEC) of surfactants and polymerization degree. The adsorption experiments of methyl orange (MO) on 3RenQ-Mt and 2RenQ-Mt were studied using batch method as a function of the concentration of surfactants, contact time, pH and temperature. The optimal conditions for MO on 3RenQ-Mt and 2RenQ-Mt were as follows: 1.0 CEC of the concentration of surfactants, contact time of 6 h, natural pH of 3, the temperature of 20 °C, the equilibrium adsorption capacity of 3RenQ-Mt and 2RenQ-Mt reached to 85.97 and 98.07 mg g − 1 , respectively; at the same experimental condition, 3RenQ-Mt exhibited the stronger interaction with MO than 2RenQ-Mt. The kinetic data were better described by the pseudo-second order kinetics model. The adsorption isotherm was in good agreement with the Langmuir model. Thermodynamic parameters such as the Gibbs free energy ΔG θ , the standard enthalpy ΔH θ and the standard entropy ΔS θ confirmed that the process of MO adsorption was spontaneous, exothermic, physisorption and randomness decreasing. [ABSTRACT FROM AUTHOR]

Oligomeric surfactants with multiple hydrophobic and hydrophilic groups are an attractive novel surfactant with improved properties and functionalities compared with those of conventional monomeric surfactants. In this study, linear- and star-type quaternary ammonium salt-based trimeric surfactants, 3C n lin- s -Q and 3C n tris- s -Q, were synthesized with different alkyl chain lengths (n), spacer chain lengths (s), and spacer skeletons (linear or star) and their adsorption and aggregation properties were characterized by electrical conductivity, surface tension, fluorescence, viscosity, dynamic light scattering (DLS), and small-angle X-ray scattering (SAXS). Trimeric surfactants exhibited high water solubility despite containing three alkyl chains. Conversely, the linear-type trimeric surfactant 3C 14 lin-3-Q, composed of rigid short spacer chains and long alkyl chains, exhibited low water solubility. The adsorption and orientation of trimeric surfactants at the air/water interface depended on the alkyl chain length, spacer chain length, and spacer skeleton, and the effect of alkyl chain length was dominant. The star-type trimeric surfactant 3C 12 tris-6-Q was efficiently adsorbed and oriented at the air/water interface, despite its long spacer and bulky skeleton, which extended from the center of the amino group in the spacer. Therefore, trimeric surfactants with high performance and advanced functionalities were successfully achieved. This study provides insights into the molecular design and synthesis of trimeric surfactants for future application in various industrial fields. [Display omitted] • Studied linear- and star-type quaternary ammonium salt-based trimeric surfactants. • Majority of trimeric surfactants show excellent solubilities in aqueous solutions. • Critical micelle concentration (CMC) depends on alkyl chain length. • The adsorption properties are especially influenced by the alkyl chain length. • Increase in alkyl and spacer chain lengths cause slight increase in micellar size. [ABSTRACT FROM AUTHOR]

We investigated the aggregation behavior of star-type trimeric surfactants (3C 12 trisQ) with a hydrocarbon chain length ( n ) of 12 in sodium salicylate (NaSal) aqueous solution at various surfactant ( C D ) and salt concentrations ( C S ) using small-angle X-ray scattering (SAXS) and rheological measurements. At a low surfactant concentration ( C D = 7 mM), 3C 12 trisQ aggregates in solution evolved from ellipsoidal micelles, to rodlike or wormlike micelles and finally to multi-lamellar vesicles (MLVs) with increasing C S . In contrast, at higher surfactant concentrations ( C D = 14 and 28 mM), we did not observe vesicle formations of 3C 12 trisQ because 3C 12 trisQ were insoluble in solution at higher NaSal concentrations. The structural transitions of the 3C 12 trisQ aggregates strongly depended on both C S and C D . We also compared the MLV structure formed by 3C 12 trisQ with that formed by gemini-type surfactants (12-2-12). The repeat distance of the 3C 12 trisQ MLV (33.95 Å) was remarkably larger than that of the 12-2-12 (22.36 Å). We found that introducing spacer chains, i.e., from dimeric to trimeric surfactants, caused a decrease in NaSal concentrations at which micelle-to-vesicle transitions were observed. [ABSTRACT FROM AUTHOR]

• A novel star-shaped cationic surfactant, 3C 22 quinQ, was designed and synthesized. • 3C 22 quinQ is significantly effective in altering wettability of water-wet quartz surface. • The wettability alteration is primarily dependent on the surfactant adsorption layer. • Surfactant adsorption is affected by charge numbers of head group and hydrophobic interaction of tail chains. Wettability alteration is a crucial method to mitigate water blockage damage in tight oil reservoirs. Novel star-shaped trimeric cationic surfactant, namely 3C 22 quinQ comprising three long-tailed quaternary ammonium surfactants, was synthesized and investigated as a new highly effective wetting alternation agent. This paper focuses on the adsorption behavior and the ability of 3C 22 quinQ to alter wettability of water-wet quartz surface. The contact angle data of the solid–liquid interface in an oil/water/solid three-phase system reveal that, as compared to monomeric and Gemini cationic surfactants, 3C 22 quinQ is a more effective wetting agent for water-wet quartz surfaces at lower concentrations. SEM-EDS analysis and AFM measurements showed that the formation of surfactant adsorption on the quartz surface and the adsorption layer was mostly responsible for the wettability change. DFT analysis revealed the propensity to accept electrons and favorable interaction between 3C 22 quinQ and silica, and that the head group region containing quaternary ammonium ions was adsorption active site. MD simulations showed 3C 22 quinQ was adsorbed on the quartz surface spontaneously by calculating adsorption energy, and the bilayer adsorption structure of 3C 22 quinQ was acquired at the silica surface. Combination of experimental and theoretical results inferred that the wettability properties of quartz surface were determined by charge numbers of head group and hydrophobic interaction of tail chains. This work has the potential to provide insight on the development and design of highly effective wettability alternating agent. [ABSTRACT FROM AUTHOR]

The properties of quaternary ammonium salt-type cationic trimeric surfactants (m-2-m-2-m, m represents the carbon atom number in alkyl chain lengths of 8, 10, and 12) and oppositely charged anionic monomeric surfactant, sodium n-octyl sulfate (SOS), were characterized by employing several techniques such as static surface tension, fluorescence spectroscopy, and dynamic light-scattering measurements. The critical micelle concentrations (cmc) of m-2-m-2-m were much lower than those of the corresponding dimeric and monomeric surfactants, and decreased with increasing chain length. The addition of SOS to m-2-m-2-m solutions resulted in a further decrease of the cmc. The mixed surfactants showed higher efficiencies in lowering the surface tension than the individual surfactants. The fluorescence measurements suggested the formation of mixed micelles with a hydrophobic environment in the solutions even at lower concentrations. The dynamic light-scattering study indicated the presence of two different kinds of aggregates with different hydrodynamic diameters. The larger one was attributed to the mixed micelle of m-2-m-2-m and SOS. These results indicated a decline of the electrostatic repulsion between cationic head groups through the incorporation of anionic surfactant into the mixed surfactants. [Copyright &y& Elsevier]

Trimeric-type anionic surfactants (3CntaAm, where n is a hydrocarbon chain length of 8, 10, or 12) with three hydrocarbon chains and three carboxylate headgroups were synthesized from tris(2-aminoethyl)amine, and their properties were investigated by surface tension, electrical conductivity, dynamic and static light-scattering, fluorescence of pyrene, and emulsification power techniques. The critical micelle concentrations (CMC) of 3CntaAm were 0.00092–0.00834 mmol dm−3, and the surface tensions at the CMC were 33.3–39.9 mN m−1. The areas per molecule occupied by 3C10taAm and 3C12taAm were extremely small, showing they were highly compact at the air/water interface. In addition, adsorption or micellization behavior of 3CntaAm was estimated by parameters such as p C 20 (the efficiency of surface adsorption), CMC/ C 20 (the ease of adsorption relative to the ease of micellization), and Δ G M o (Gibbs energy of micellization). Dynamic and static light-scattering mesurements of 3CntaAm showed a hydrodynamic radius of 45–61 nm above the CMC and aggregation numbers of 10–82 at the CMC, respectively. The fluorescence intensity ratio of the first to the third band in the emission spectra of pyrene started to lower from far above the CMC for 3C8taAm and 3C10taAm, and below the CMC for 3C12taAm. This suggests that loose micelles or premicellar aggregates are formed in solutions. Mixtures of aqueous solutions of 3CntaAm and toluene formed oil-in-water-type emulsions, and the stabilizing abilities were in the order of 3C8taAm>3C10taAm>3C12taAm. The degree of emulsification of 3C8taAm remained at 69% after 24 h of standing. Thus, 3CntaAm exhibited unique properties superior to monomeric or dimeric surfactants that were significantly influenced by their hydrocarbon chain lengths. [ABSTRACT FROM AUTHOR]

Trimeric surfactants of quaternary ammonium bromide (m-2-m-2-m, where m is the hydrocarbon chain length of 8, 10, or 12) with three hydrocarbon chains and three hydrophilic groups connected by two ethylene spacer chains were synthesized by the reaction of N,N,N′,N″,N″-pentamethyldiethylenetriamine and the corresponding alkyl bromide. Their physicochemical properties were characterized by surface tension, static and dynamic light-scattering, and fluorescence spectrum of pyrene techniques. The critical micelle concentrations (cmc''s) of m-2-m-2-m shifted to lower concentrations with increasing hydrocarbon chain length, and their values were smaller by about one to three orders of magnitude than those of the corresponding dimeric (m-2-m) and monomeric surfactants (CmTAB) with the same hydrocarbon chain length. Of these surfactants, 10-2-10-2-10 showed the greatest efficiency in lowering the surface tension and provided the smallest occupied area per molecule, indicating that it adsorbs more compactly at the air/water interface. In addition, from the static and dynamic light-scattering measurements, the aggregation numbers of the trimeric surfactants at the cmc were very small, and two hydrodynamic diameters above the cmc were observed. [Copyright &y& Elsevier]

The solubilization ability of surfactants is closely related to their molecular design. The number of alkyl chains in a surfactant molecule accordingly affects the forming of micellar structures. In the present study, the solubilization ability of cationic surfactants was studied by changing number of alkyl chains by using one of these three types of surfactants: star-shaped trimeric quaternary ammonium bromides (tris(N -alkyl- N , N -dimethyl-2-ammoniumethyl)amine bromides (3C n trisQ, n = 10, 12, and 14 is the number of carbon atoms in the alkyl chains)), dimeric surfactants (1,2-bis(alkyldimethylammonio)ethane dibromide (n -2- n , n = 10, 12, and 14)), and dodecyltrimethylammonium bromide (DTAB). The solubilization abilities of the above surfactants were studied using naphthalene and stearic acid at 298.2 K. Judging from the value of the molar solubilization ratios (MSR) for naphthalene and stearic acid, the solubilization ability generally improved as the number of alkyl chains of the surfactant molecules increased, as follows: DTAB <12-2-12 < 3C 12 trisQ. The Gibbs free energy change (Δ G 0) values for the solubilization of naphthalene and stearic acid into 3C 12 TrisQ solutions were relatively large negative numbers, −28.3 and −59.4 kJ mol−1, respectively. Moreover, small angle X-ray scattering analysis indicated that electron density at the ellipsoidal micellar surface of 3C 12 trisQ was decreased by solubilizing naphthalene and stearic acid, however, the micellar shape was not drastically changed from ellipsoidal micelle. These results indicated that the trimeric surfactant presented better potential as solubilizer compared to typical monomeric surfactants. Unlabelled Image • Number of alkyl chains in a surfactant molecule affects the solubilization ability. • The solubilization ability of trimeric, dimeric, and monomeric surfactants was studied using solubilizates. • The molar solubilization ratios were increased as the number of alkyl chains of the surfactant. • The trimeric surfactant presented better potential as solubilizer compared to typical monomeric surfactants. [ABSTRACT FROM AUTHOR]

This work reports that cationic micelles formed by cationic trimeric, tetrameric, and hexameric surfactants bearing amide moieties in spacers can efficiently kill Gram-negative E. coli with a very low minimum inhibitory concentration (1.70-0.93 μM), and do not cause obvious toxicity to mammalian cells at the concentrations used. With the increase of the oligomerization degree, the antibacterial activity of the oligomeric surfactants increases, i.e., hexameric surfactant > tetrameric surfactant > trimeric surfactant. Isothermal titration microcalorimetry, scanning electron microscopy, and zeta potential results reveal that the cationic micelles interact with the cell membrane of E. coli through two processes. First, the integrity of outer membrane of E. coli is disrupted by the electrostatic interaction of the cationic ammonium groups of the surfactants with anionic groups of E. coli, resulting in loss of the barrier function of the outer membrane. The inner membrane then is disintegrated by the hydrophobic interaction of the surfactant hydrocarbon chains with the hydrophobic domains of the inner membrane, leading to the cytoplast leakage. The formation of micelles of these cationic oligomeric surfactants at very low concentration enables more efficient interaction with bacterial cell membrane, which endows the oligomeric surfactants with high antibacterial activity.