Surface tension and micellization properties of heterogemini surfactants containing quaternary ammonium salt and sulfobetaine moiety

Synthesis and characterization of novel acrylamide derivatives and their use as corrosion inhibitors for carbon steel in hydrochloric acid solution

Two new acrylamide derivatives were prepared namely: "N-(bis(2-hydroxyethyl) carbamothioyl) acrylamide (BHCA) and N-((2-hydroxyethyl) carbamothioyl) acrylamide( HCA) and their chemical structures were analyzed and confirmed using IR and 1H NMR". These chemicals were investigated as corrosion inhibitors for carbon steel (CS) in 1 M HCl medium using chemical method (mass  loss, ML), and electrochemical techniques including potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS). The results showed that the acrylamide derivatives work well as corrosion inhibitors, with inhibition efficacy (%IE) reaching 94.91-95.28% at 60 ppm for BHCA and HCA, respectively. Their inhibition depends mainly on their concentration and temperature of the solution. According to the PDP files, these derivatives function as mixed-type inhibitors that physically adsorb on the CS surface in accordance with the Langmuir adsorption isotherm, creating a thin coating that shields the CS surface from corrosive fluids. The charge transfer resistance (R_ct) increased and the double layer capacitance (C_dl) decreased as a result of the adsorption of the used derivatives. Calculated and described were the thermodynamic parameters for activation and adsorption. Quantum chemistry computations and Monte Carlo simulations were examined and discussed for these derivatives under investigation. Surface analysis was checked using atomic force microscope (AFM). Validity of the obtained data was demonstrated by the confirmation of these several independent procedures.

Investigating bolalipids as solubilizing agents for poorly soluble drugs: Effects of alkyl chain length on solubilization and cytotoxicity

Synthetic single-chain bolalipids with symmetrical headgroups have shown potential in various pharmaceutical applications, such as the stabilization of liposome bilayers. Despite their amphiphilic character, synthetic bolalipids have not yet been investigated for their suitability as solubilizing agents for poorly soluble drug compounds. In this study, three synthetic single-chain bolalipids with increasing alkyl chain lengths (C22, C24 and C26) were investigated. All three bolalipids were able to achieve an increased solubility of the model drug, mefenamic acid, by approximately 180% in a pH 7.4 buffer compared to only a 102-105% increase achieved by sodium dodecyl sulfate (SDS) or the non-ionic surfactant pegylated hydroxystearate (PEG-HS). Subsequently, interfacial activity of bolalipids and their ability to destabilize liposomal bilayers were investigated. The C22 bolalipid exhibited a consistently lower interfacial activity, which was consistent with its significantly lower cytotoxicity in the macrophage-like cell line, J774. A1, compared to C24 and C26 counterparts. The mean IC₅₀ values of the bolalipids tested (0.035-0.093 mM) were approximately 4-100-fold lower than that of SDS (0.401 mM) or PEG-HS (0.922 mM), with the mechanism of toxicity linked to increased cell membrane permeability, as is expected for surfactants. In summary, evidence from this study shows that decreasing the length of the bolalipid alkyl linker from C26 to C22 resulted in a significantly decreased cytotoxicity with no loss in drug solubilization efficiency.

Supramolecular Vector/Drug Coassemblies of Polyglycerol Dendrons and Rutin Enhance the pH Response

A coassembly strategy for a supramolecular vector/drug was proposed with a biocompatible ternary dodecyl-bi(third-generation polyglycerol (PG) dendrons) (C₁₂-(G3)₂) amphiphile, dodecyl sulfobetaine (SB3-12) surfactant, and poorly water-soluble drug rutin. C₁₂-(G3)₂ and rutin will mutually enhance their pH response by protonation and deprotonation of dendritic PG and rutin's ionization as the pH changes from the acidic gastric lumen to the weakly alkaline intestine. SB3-12 may increase the payload and bring about sustained release for rutin by intermolecular interactions. Self-assembling behaviors of C₁₂-(G3)₂, SB3-12, sodium dodecyl sulfate (SDS), and dodecyl trimethylammonium bromide (DTAB) and their hybrids with rutin were characterized by UV-vis spectroscopy, a fluorescence probe, and ¹H NMR. UV-vis and ¹H NMR were used to identify the position and orientation of rutin in the vectors. The functions of the vector/drug were confirmed by measuring the solubility and in vitro release of rutin. The ternary coassembling vector/drug easily imparted functions of pH-responsive and sustained release without complex synthetic processes. The nanocaves framed by PG dendrons in the micelles provide pH-responsive compartments for rutin and SB3-12 in the supramolecular vector/drug anchors that accommodate rutin by weak interactions. The finely matched supramolecular vector/drug coassemblies exhibit the pH-responsive function for a potential application in the treatment of inflammatory bowel disease.

Improved remediation of co-contaminated soils by heavy metals and PAHs with biosurfactant-enhanced soil washing

Due to the huge toxicity of co-contaminated soil with PAHs and heavy metals and the complexity of their remediation, it is thus critical to take effective remediation actions to remove heavy metals and PAHs simultaneously from the co-contaminated soil. Biosurfactant-enhanced soil washing (BESW) were investigated in this study for remediation of soil co-contaminated with phenanthrene (PHE) and cadmium (Cd). The co-existence of PHE and Cd caused the change of the structure of soil and rhamnolipid micelle, which lead to different removal rate of PHE and Cd from co-contaminated soil compared with single contaminated soil. The results of FT-IR and NMR showed that PHE entered micelles of rhamnolipid and Cd formed the complexation with the external carboxyl groups of rhamnolipid micelle. We also found that pH, concentration of rhamnolipid solution, temperature and ionic strength had influence on co-contaminated soil remediation. The effects of above mentioned four factors on co-contaminated soil remediation in BESW processes were analyzed by using Taguchi design of experiment method. Taguchi based Grey Relational Analysis was conducted to identify the optimal remediation conditions, which included pH = 9, concentration of rhamnolipid = 5 g/L, temperature = 15 °C and ionic strength = 0.01 M. Under the optimal conditions for BESW, removal rates of cadmium and phenanthrene reached 72.4% and 87.8%, respectively in co-contaminated soil.

Rational design of dynamic imine surfactants for oil-water emulsions: Learning from oil-induced reversible dynamic imine bond formation

HYPOTHESIS

Dynamic imine surfactants (DIS) can be constructed by the formation of dynamic imine bonds (Dibs) between aromatic aldehydes and aliphatic amines in water. Because of the nature of Dibs in water, a thermodynamic equilibrium state was achieved between the DIS and aldehyde and amine precursors to form a dynamic combinatorial library (DCL). When the DIS served as sole emulsifier to form oil-H₂O emulsions, the precursors migrated between the H₂O phase and the oil phase, which altered the DCL equilibrium. The DIS concentration and emulsion stability also changed.

EXPERIMENTS

By mixing 4-(2-sulfobetaine-ethoxy)-benzaldehyde (SBBA) and aliphatic amines of C_nH_2n+1NH₂ (n = 4, BA; n = 6, HA; n = 8, OA; n = 10, DA) in water, four amphoteric DIS (SBBA-BA/HA/OA/DA) were prepared. Dib formation was characterized using ¹H NMR. The DIS surface activity was studied by surface tension and fluorescence probe methods. The reversible switching of DIS and its wormlike micelles were explored.

FINDINGS

SBBA-OA (or SBBA-DA) DIS was not a suitable emulsifier for stable hydrocarbon (HC)-H₂O emulsions. OA and DA were more soluble in the HC phase than the H₂O phase. The precursors of OA and DA migrated from the H₂O to the HC phase, and the thermodynamic equilibrium state of DCL shifted towards Dib dissociation. The Dib could be regenerated by HC phase removal. A novel strategy where volatile HC (such as pentane) was used as a trigger was developed to switch the DIS reversibly and its self-assemblies (such as wormlike micelles) in water without inorganic salt accumulation. The SBBA-HA (or SBBA-BA) DIS was a suitable emulsifier for stable emulsions because HA and BA were more soluble in the H₂O phase.

Synthesis and Properties of Alkyl Bis-Guanidinium Acetates Surfactants

Novel surfactants with double hydrophilic groups (cocopropane and tallowpropane bis-guanidinium acetates), were synthesized and tested to evaluate both the basic surfactant properties and the unique application performance. Surface tension, conductivity and contact angle measurements were used to study the self-aggregation behavior in aqueous solution. Aggregation parameters were calculated such as adsorption efficiency and effectiveness (pC20 and CAC/C20), the maximum surface excess concentration (Гmax) and minimum surface area permolecule (Amin). The thermodynamic parameters of aggregation based conductivity measurements revealed that the aggregation process was spontaneous and entropy-driven. Compared to DTAC and CTAC, the alkyl bis-guanidinium acetates showed a higher emulsification capacity with both liquid kerosene and soybean oil. The evaluation of antimicrobial activity showed that the alkyl bisguanidinium acetates exhibited strong antibacterial activity against the tested strains at a concentration of 50 ppm.

Determination of Critical Micellar Concentration of Homologous 2-Alkoxyphenylcarbamoyloxyethyl-Morpholinium Chlorides

The critical micellar concentrations of selected alkyloxy homologues of local anesthetic 4-(2-{[(2-alkoxyphenyl)carbamoyl]oxy}ethyl)morpholin-4-ium chloride with n_c = 2, 4, 5, 6, 7, 8, and 9 carbons in alkyloxy tail were determined by absorption spectroscopy in the UV⁻vis spectral region with the use of a pyrene probe. Within the homologous series of the studied amphiphilic compounds, the ln(cmc) was observed to be dependent linearly on the number of carbon atoms n_c in the hydrophobic tail: ln(cmc) = 0.705⁻0.966 n_c. The Gibbs free energy, necessary for the transfer of the methylene group of the alkoxy chain from the water phase into the inner part of the micelle at the temperature of 25 °C and pH ≈ 4.5⁻5.0, was found to be −2.39 kJ/mol. The experimentally determined cmc values showed good correlations with the predicted values of the bulkiness of the alkoxy tail expressed as the molar volume of substituent R, as well as with the surface tension of the compounds.

Synthesis, surface activities, and aggregation behavior of phenyl-containing carboxybetaine surfactants

A novel series of carboxybetaine surfactants were synthesized for the first time and their physicochemical properties were systematically investigated.

Physicochemical Properties of Amino Acid Surfactants and Their Use in Dyeing with Natural Plant Dyes

Environment-friendly green amino acid surfactants were prepared by the reaction of glutamic acid with various fatty acids (C2–C14). These green amino acid surfactants have been found to exhibit good surface activities i.e. surface tension, foaming, wetting power and emulsifying ability. The critical micelle concentration (CMC) increases with an increase of the alkyl chain of amino acid surfactants. After 5 days the biodegradation of these amino acid surfactants was larger than 60% and consequently, the surfactants should be regarded as readily biodegradable. Finally, the green amino acid surfactants were added to natural plant dyes to test their applicability for dyeing wool fibers. The surfactant developed in this study will contribute to green and sustainability chemistry.

Structure and Rheology of Wormlike Micelles Formed by Fluorocarbon-Hydrocarbon-Type Hybrid Gemini Surfactant in Aqueous Solution

The structure and rheological properties of wormlike micelles formed by a fluorocarbon-hydrocarbon-type hybrid gemini surfactant in an aqueous solution were investigated by means of small-angle X-ray scattering (SAXS) and viscoelastic measurements. The cross-sectional structure (the radius of the hydrophobic core and the thickness of the hydrophilic shell) and the aggregation number per unit axial length of wormlike micelles were evaluated by a model fitting analysis of SAXS profiles. Both parameters for the hybrid gemini surfactant were smaller than those of a corresponding hydrocarbon-hydrocarbon-type gemini surfactant. On the other hand, the viscosity of the hybrid gemini surfactant was higher than that of the hydrocarbon-hydrocarbon-type gemini surfactant. From the viscoelastic parameters, the steady state compliance, J_e, and the terminal relaxation time, τ_w, which were independently obtained by dynamic viscoelastic measurement, we revealed that a larger number of entanglements and a longer contour length of the hybrid gemini surfactant led to the higher viscosity. These results obtained by the rheological measurements were consistent with those obtained by SAXS analysis.

Quaternary Ammonium Gemini Surfactants Used in Enhanced Oil Recovery: Synthesis, Properties, and Flooding Experiments

In this work, quaternary ammonium gemini surfactants with different spacers and lipophilic tails were synthesized by using imidazole and halogenated hydrocarbons as raw materials. The surfactants were characterized by EA, IR, and ESI-MS. Physico-chemical properties including critical micelle concentration (CMC), surface tension at CMC (γCMC), saturated adsorption amount (Γmax), occupied area per molecule (Amin), standard free energy of micellization (ΔG0m) and adsorption (ΔG0ads), as well as the oil/water interfacial tension were completely studied. The prepared surfactants could efficiently lower the interfacial tension at water/air interfaces and oil/water interfaces. The results indicate that the ability of reducing the surface tension was affected by the surfactant arrangement, which could be further adjusted by a spacer and lipophilic tail. Accordingly, four surfactants were chosen as the representatives to evaluate the displacement efficiency in flooding experiments via using the authentic sandstone microscopic model.

Interactions of Sulfobetaine Zwitterionic Surfactants with Water on Water Surface

We carried out a combined study using surface tension, phase-sensitive frequency generation (SFG) vibrational spectroscopy, and MD simulations to investigate the industrially relevant zwitterionic surfactant N-dodecyl-N, N-dimethyl-3-ammonio-1-propanesulfonate (DDAPS) on water surface. The SFG Im(χ⁽²⁾) spectra showed that the interaction between DDAPS and water was different from those between biologically relevant zwitterionic phospholipids and water. While zwitterionic phospholipids were found to be anionic-like and flipped water molecules with their OHs pointing toward the air, DDAPS oriented water molecules with their OHs mostly pointing toward the liquid water. We built a new force field for the MD simulation which produced the correct surface tension of water with various DDPAS coverage. The MD simulation showed that the head groups of DDPAS were nearly parallel to the water surface. When the surface coverage of DDPAS was increased, the averaged tilting angle of DDPAS's tails decreased, but it had little effect on the orientation of the headgroup. The sulfobetaine zwitterionic surfactant was found to be more cationic-like because the positively charged group was more capable of orienting interfacial water.

Syntheses of Tartaric Acid-Based Hybrid Gemini Surfactants Containing Fluorocarbon and Hydrocarbon Chains

Tartaric acid-based symmetric and hybrid gemini surfactants having dodecyloxy (C12H25O-) and tridecafluoro nonyloxy groups (C6F13(CH2)3O-) as hydrophobic groups were synthesized, and their surface properties were studied by surface tension (γ)-concentration and surface pressure-area (π-A) measurements. All geminis showed superior surfactant properties to 1+1 type surfactant. Especially, hybrid gemini showed high efficiency of lowering the surface tension comparable to that of bis(C6F13(CH2)3O) gemini. Further, hybrid gemini showed an unusual existence of two breakpoints at γ = ∼25 and 18 mN m−1. In the π-A measurements, regardless of symmetric or hybrid structures, geminis having fluoroalkyl group formed only liquid condensed monolayers while the bis(dodecyloxy) gemini formed solid monolayer. Molecular occupied areas of hybrid gemini were subequal to the mean of those of symmetric geminis.

Synthesis and Interfacial Activity of Novel Heterogemini Sulfobetaines in Aqueous Solution

Three new heterogemini sulfobetaines and their chloride salts were synthesised. The interfacial activities of the obtained chlorides in aqueous solution were studied by equilibrium and dynamic surface tension measurements. The critical micelle concentration, surface excess concentration, minimum area per surfactant molecule and standard Gibbs energy of adsorption as well as micelle lifetime and diffusion coefficient were determined. The adsorption properties and micelle lifetime of these compounds significantly depend on the length of alkyl chain. The critical micelle concentration decreases with increasing chain length of the compounds considered. The values of the diffusion coefficient of N-alkyl-N-methyl-N-(3-sulfopropyl)-6-(N-alkyl-N-methylamino)hexylammonium chloride tend to decrease as the concentration is increased.

A Novel Synthesis of Anionic Heterogemini Surfactants Containing COOH, SO3H and PO(OH)2 Headgroups from Corynomicolic Acid and its Derivatives

Anionic heterogemini surfactants with –COOH, –SO3H and –PO(OH)2 headgroups in combination were synthesized from Corynomicolic acid derivatives having R = C11H23. The –SO3H headgroup was obtained by the successive conversion of OH → OMs → SCN → SH → –SO3H. The PO(OH)2 headgroup was introduced by the conjugate-addition to E-isomer of α,β-unsaturated ester derived from Corynomycolic acid ester. Heterogemini surfactant with –SO3H and –PO(OH)2 headgroups was also synthesized from phosphonate analog of Corynomycolic acid. The stereoisomers (syn- and anti-isomers) of heterogemini surfactants were separately prepared except for heterogemini surfactants with –COOH and –PO(OH)2 headgroups. Effects of variation and stereochemistry of two anionic headgroups on their surfactant properties were also studied on the basis of surface tension measurements.

Synthesis and Surface Properties of Novel Gemini Surfactants

Novel Gemini surfactants containing amide group linkage were prepared with fatty acid, diamine and dihalide by simple organic reaction, and characterized with IR, and elemental analysis (EA). As the results show, the structures of the products obtained correspond to the target compounds designed. By surface tension scanning, these Gemini surfactants have excellent surface activity with low c.m.c. and surface tension, the lowest c.m.c value was 9.12 × 10−6 mol/L for surfactant Bi-18(4).

Surface-active properties of nitrogen heterocyclic and dialkylamino derivates of hexadecylphosphocholine and cetyltrimethylammonium bromide

The physico-chemical properties of dialkylamino and nitrogen heterocyclic analogues of hexadecylphosphocholine (HPC) and cetyltrimethylammonium bromide (CTAB) were investigated. The surface properties, such as the critical micelle concentration (cmc), the surface tension value at the cmc (gamma(cmc)), and the surface area at the surface saturation per head group (A(cmc)) were determined by means of surface tension measurements. Micelle size was determined using the dynamic light scattering method. The influence of dialkylamino groups and heterocyclic ring size on surface-active properties was investigated. Surface activity and micellar size of prepared analogues of HPC and CTAB were mutually compared.

Adsorption and aggregation properties of heterogemini surfactants containing a quaternary ammonium salt and a sugar moiety

A novel heterogemini surfactant comprising two hydrocarbon chains and two different hydrophilic groups such as a quaternary ammonium cation and gluconamide nonion N,N-dimethyl-N-[2-(N'-alkyl-N'-gluconamide)ethyl]-1-alkylammonium bromides (2CnAmGlu, where n represents hydrocarbon chain lengths of 8, 10, 12, and 14) was synthesized by reacting N,N-dimethylethylenediamine with alkyl bromide, followed by a reaction with 1,5-D(+)-gluconolactone. The adsorption properties of 2CnAmGlu were characterized by surface tension measurements made using the Wilhelmy plate method, and their aggregation properties were investigated by dynamic light scattering and cryogenic transmission electron microscopy techniques. The relationship between the hydrocarbon chain length and the logarithm of the critical micelle concentration (cmc) for 2CnAmGlu exhibited a linear decrease when the chain length was increased up to 12 and then a departure from linearity at n=14. The surface tension reached 24-26 mN m-1 at each cmc, indicating high efficiency in lowering the surface tension of water. Furthermore, it was found that the structure of the aggregate formed for 2CnAmGlu in solution was influenced by the hydrocarbon chain length; that is, for n=10 and 12, micelles with a hydrodynamic radius of 2-5 nm were formed, whereas vesicles were also observed for n=14.