Imidazolium Surfactants Research Articles

Synthesis, self-assembly and surface-active properties of alkyl halide mediated imidazolium monomeric surfactants

Two imidazolium monomeric surfactants, that is, 1-tetradecyl-1H-imidazole [14IM] and 1-hexadecyl-1H-imidazole [16IM] has been synthesized and characterized by 1H NMR,13C NMR, FTIR, HRMS spectroscopies and thermogravimetric analysis (TGA) for number and types of protons and carbon, functional groups, estimation of molecular weight and thermal stability of these compounds. The conductivity was measured in double distilled water at four different temperatures, 288, 293, 298, and 303 K. The results showed that these surfactants behave as weak electrolytes. The density and viscosity data have shown the existence of strong interactions between imidazolium surfactants and solvent (water) molecules. The results obtained from Root’s equation indicate that surfactant–solvent interactions are important than surfactant–surfactant interactions in dilute solutions, that is, below critical micellar concentration. The values of constants obtained from Einstein and Moulik equations have revealed that there was stronger and significant interaction between imidazolium surfactants and water molecules below critical micellar region. The surface tension parameters have indicated that these surfactants are good contenders to lower the surface tension of air/water interface. The results obtained from surface tension data have shown that standard change in free energy of micellization (ΔG°mic) and adsorption (ΔG°ads) were negative, indicating that these surfactants molecules have spontaneous tendencies to form micelles in solution at higher concentration and to get adsorb at the air/water interface at lower concentration. The TGA has indicated good thermally stability and activation energy for thermal decomposition was found in the range of 37.26.26–98.20.20 kJ/mol.

Self-assembly of the imidazolium surfactant in aprotic ionic liquids. The anion effect of aprotic ionic liquids.

The structure of ionic liquids (ILs) has an influence on their physiochemical properties, determining their performance as self-assembly media. In this study, we focus on the anion effect of aprotic ionic liquids (AILs). The aggregation behaviours of the cationic surfactant 1-hexadecyl-3-methylimidazolium bromide (C16mimBr) have been investigated in the imidazolium AILs with the 1-ethyl-3-methyl imidazolium cation and different anions, including nitrate, ethylsulfate, bis(trifluoromethylsulfonyl) imide and tetrafluoroborate. Surface adsorption parameters of C16mimBr were determined using surface tension measurements, and the critical micellization concentration values in AILs vary for their different cohesive energy. The micellar and lamellar lyotropic liquid crystal phases emerge with the increase of C16mimBr concentrations. The structure and properties of aggregates were determined using small angle X-ray scattering, polarized optical microscopy, rheology and differential scanning calorimetry. The anion effects of AILs on the phase behaviours and structure and properties of aggregates were analysed and discussed. The lamellar lyotropic liquid crystals have shown good conductivity, as confirmed by electrochemical impedance spectroscopy characterization. Our results enhance the understanding of the structure effect of ILs as self-assembly media and contribute to the design of tailorable solvents.

A hybrid ionic liquid crystal comprising imidazolium surfactant-graphene oxide

ABSTRACT To produce graphene oxide liquid crystal composites with better controllability, imidazolium surfactant with biphenyl mesogenic core (CBphCM) has been synthesised and used to modify the negatively charged surface of graphene oxide (GO) to obtain a hybrid ionic liquid crystal (CBphCM-GO). The process of GO and CBphCM recombination was monitored by various experimental techniques such as FT-IR, Uv-vis, Raman and XPS. The experimental results indicated that the C=O bonds on GO sheets are all reduced and C−O bonds are partially reduced due to the imidazolium units being electrically active and nitrogen-rich, and the presence of the N−O bonds indicates that a new hybrid is formed between CBphCM and GO. The recombination destroys the electrostatic repulsion balance among the GO lattices, and the CBphCM-GO is observed a fluffy appearance by TEM. The liquid crystal properties of CBphCM and CBphCM-GO were investigated by DSC, polarised optical microscopy (POM) and variable temperature X-ray diffraction, respectively. As an ionic liquid crystal, CBphCM has SmA as well as the rare SmC phases exhibits de Vries-like behaviour with a layer shrinkage. The liquid crystal properties of CBphCM-GO are derived from CBphCM, and the layer shrinkage behaviour from SmA to SmC phase has also been observed.

Synthesis, physical properties and cytotoxic assessment of ester-terminated gemini imidazolium surfactants

Ester-functionalized gemini imidazolium amphiphiles appended with different spacers have been developed. The desired structures were confirmed using mass spectroscopy and NMR techniques. With the help of tensiometry, conductometry, and spectrofluorometry, the investigated amphiphiles have been characterized for a variety of physical properties including Gibbs free energy of adsorption (ΔG0ads), C20 (surfactant concentration required to reduce the surface tension of the solvent by 20 mN•m−1), maximum surface excess (Ʈmax), critical micelle concentration (cmc), Gibbs free energy of the micellization (ΔG0mic) and Amin (minimum surface area/molecule). Dynamic light scattering (DLS) measurements were taken to examine aggregate size distribution and zeta potential. Thermal decomposition temperature of investigated amphiphiles was determined from thermogravimetric analysis (TGA) analysis. By using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, the toxicity of examined amphiphiles towards the C6 glioma cell line was assessed. The physicochemical study of these surfactants revealed that varying spacer length considerably affects the properties.

Role of Polyanions and Surfactant Head Group in the Formation of Polymer-Colloid Nanocontainers.

This study was aimed at the investigation of the supramolecular systems based on cationic surfactants bearing cyclic head groups (imidazolium and pyrrolidinium) and polyanions (polyacrylic acid (PAA) and human serum albumin (HSA)), and factors governing their structural behavior to create functional nanosystems with controlled properties. Research hypothesis. Mixed PE-surfactant complexes based on oppositely charged species are characterized by multifactor behavior strongly affected by the nature of both components. It was expected that the transition from a single surfactant solution to an admixture with PE might provide synergetic effects on structural characteristics and functional activity. To test this assumption, the concentration thresholds of aggregation, dimensional and charge characteristics, and solubilization capacity of amphiphiles in the presence of PEs have been determined by tensiometry, fluorescence and UV-visible spectroscopy, and dynamic and electrophoretic light scattering. The formation of mixed surfactant-PAA aggregates with a hydrodynamic diameter of 100-180 nm has been shown. Polyanion additives led to a decrease in the critical micelle concentration of surfactants by two orders of magnitude (from 1 mM to 0.01 mM). A gradual increase in the zeta potential of HAS-surfactant systems from negative to positive value indicates that the electrostatic mechanism contributes to the binding of components. Additionally, 3D and conventional fluorescence spectroscopy showed that imidazolium surfactant had little effect on HSA conformation, and component binding occurs due to hydrogen bonding and Van der Waals interactions through the tryptophan amino acid residue of the protein. Surfactant-polyanion nanostructures improve the solubility of lipophilic medicines such as Warfarin, Amphotericin B, and Meloxicam. Surfactant-PE composition demonstrated beneficial solubilization activity and can be recommended for the construction of nanocontainers for hydrophobic drugs, with their efficacy tuned by the variation in surfactant head group and the nature of polyanions.

Complexation of Oligo- and Polynucleotides with Methoxyphenyl-Functionalized Imidazolium Surfactants.

Interaction between cationic surfactants and nucleic acids attracts much attention due to the possibility of using such systems for gene delivery. Herein, the lipoplexes based on cationic surfactants with imidazolium head group bearing methoxyphenyl fragment (MPI-n, n = 10, 12, 14, 16) and nucleic acids (oligonucleotide and plasmid DNA) were explored. The complex formation was confirmed by dynamic/electrophoretic light scattering, transmission electron microscopy, fluorescence spectroscopy, circular dichroism, and gel electrophoresis. The nanosized lipoplex formation (of about 100-200 nm), contributed by electrostatic, hydrophobic interactions, and intercalation mechanism, has been shown. Significant effects of the hydrocarbon tail length of surfactant and the type of nucleic acid on their interaction was revealed. The cytotoxic effect and transfection ability of lipoplexes studied were determined using M-HeLa, A549 cancer cell lines, and normal Chang liver cells. A selective reduced cytotoxic effect of the complexes on M-HeLa cancer cells was established, as well as a high ability of the systems to be transfected into cancer cells. MPI-n/DNA complexes showed a pronounced transfection activity equal to the commercial preparation Lipofectamine 3000. Thus, it has been shown that MPI-n surfactants are effective agents for nucleic acid condensation and can be considered as potential non-viral vectors for gene delivery.

Oxime Therapy for Brain AChE Reactivation and Neuroprotection after Organophosphate Poisoning.

One of the main problems in the treatment of poisoning with organophosphorus (OPs) inhibitors of acetylcholinesterase (AChE) is low ability of existing reactivators of AChE that are used as antidotes to cross the blood-brain barrier (BBB). In this work, modified cationic liposomes were developed that can penetrate through the BBB and deliver the reactivator of AChE pralidoxime chloride (2-PAM) into the brain. Liposomes were obtained on the basis of phosphatidylcholine and imidazolium surfactants. To obtain the composition optimized in terms of charge, stability, and toxicity, the molar ratio of surfactant/lipid was varied. For the systems, physicochemical parameters, release profiles of the substrates (rhodamine B, 2-PAM), hemolytic activity and ability to cause hemagglutination were evaluated. Screening of liposome penetration through the BBB, analysis of 2-PAM pharmacokinetics, and in vivo AChE reactivation showed that modified liposomes readily pass into the brain and reactivate brain AChE in rats poisoned with paraoxon (POX) by 25%. For the first time, an assessment was made of the ability of imidazolium liposomes loaded with 2-PAM to reduce the death of neurons in the brains of mice. It was shown that intravenous administration of liposomal 2-PAM can significantly reduce POX-induced neuronal death in the hippocampus.

Synthesis and Characterization of Imidazole Based Cationic Surfactants as Disinfectants

Citric acid-based cationic surfactants using 1-methyl imidazolium as coordinizing agent has been synthesized and characterized. The cationic surfactants is produced in excellent yields (70%) and has been examined by TGA, FTIR, 1H NMR and are found to have good surface-active properties. FTIR analysis showed the presence of ester confirmed by 1H NMR (the chemical shift value of 3.7 ppm and 3.8 ppm is due to the presence of an ester) in the surfactant. The biodegradability confirmed by BOD analysis. It is found that cationic imidazolium surfactants having surface tenstion of (12 mN/m) with chloride as a counter ion. The results show that cationic imidazolium surfactants with longer hydrophobic chains have a lower CMC value. TGA result shows good thermal properties of cationic surfactant. Invitro study of cationic surfactant over fungal cell indicates its antifungal activity (70% inhibition at 350 ppm) and its appliaction as disinfactant.

Hybrid emulsifier systems: Alkyl imidazolium lactoside surfactants derived from natural resources

A new series of hybrid surfactants comprising an imidazolium as a cation and a disaccharide as a non-ion were synthesized, and their aggregation behavior was also investigated. The synthetic approach used alkylation as an easily accessible route on an imidazole to attempt an economic production followed by coupling with bromoethyl lactoside to form lacto-imidazolium salts surfactants. The coupled surfactants were obtained in almost quantitative yield over several steps. The surfactant surface properties in aqueous media were investigated, including critical micelle concentration (CMC), Krafft temperature, and emulsion stability were studied. The CMC measurements of the alkyl imidazolium lactoside surfactants are significantly lower than normal imidazolium surfactants, while the emulsion investigations encourage the use of alkyl imidazolium lactoside surfactants owing to stabilized assemble behavior as good as APGs.

Quantitative structure–activity relationship study to predict the antibacterial activity of gemini quaternary ammonium surfactants against Escherichia coli

QSAR modeling for predicting the antifungal activities of gemini imidazolium surfactants against Candida albicans using GA-MLR methodsEly Setiawan, Karna Wijaya, Mudasir Mudasir

Aggregation behavior of the Mixed Systems based on Imidazolium Surfactant Containing Carbamate Fragment and Polyacrylic Acid

Aggregation behavior of the Mixed Systems based on Imidazolium Surfactant Containing Carbamate Fragment and Polyacrylic Acid

Pyrrole-tailed imidazolium surface-active monomers: aggregation properties in aqueous solution and polymerization behavior

Pyrrole-functionalized imidazolium surfactants PyCnMImBr with different alkyl chain lengths (n = 8, 10, 12) were synthesized and their aggregation properties in water were investigated by tensiometry and conductimetry. These studies show that PyCnMImBr surfactants present lower critical micellar concentration than their non-functionalized analogues due to (i) an increased hydrophobicity resulting from the extension of the alkyl chain length upon incorporation of pyrrole (ii) the formation of attractive π-π interactions among pyrrole moieties. The areas occupied by PyCnMImBr molecules are always higher than those of CnMImBr surfactants showing looser molecular arrangement at the air-water interface due to steric hindrance of pyrrole moieties. 1H nuclear magnetic resonance measurements have been used to shed light on the structure of the aggregates formed. In all cases, pyrrole is located inside the micellar core but for the shortest alkyl chain length, it tends to intercalate between the alkyl chains. Micelles obtained with PyC12MImBr were further used as nano-reactor to prepare water-stable polypyrrole nanoparticles. For this, we conduct the chemical polymerization of pyrrole inside the micelles using FeCl3 as oxidizing agent. Polymerization kinetics were followed by UV-spectroscopy. Combined with Infrared (IR) and Dynamic Light Scattering (DLS) measurements, we confirmed the formation of polypyrrole particles of about 4 nm that were water-stable thanks to the presence of cationic imidazolium functions on their surface.

Pore size control of monodisperse mesoporous silica particles with alkyl imidazole ionic liquid templates for high performance liquid chromatography applications

The control of pore size in mesoporous silica particles is still a topic of considerable research attention for the preparation of chromatographic packing materials. In this study, three alkyl imidazole ionic liquid surfactants ([BRIJOn-MIM]Ts (n = 2, 10, 20)) were synthesized from polyoxyethylene oleyl ether (BRIJ™On, n = 2, 10, 20), 1-methylimidazole, and p-toluenesulfonyl chloride. [BRIJOn-MIM]Ts (n = 2, 10, 20) exhibited different template behaviors in the preparation of mesoporous silica, and hollow silica with worm-like vesicle structures, spherical silica, and gel were obtained, respectively. Monodisperse sub-3 µm core-shell silica particles (CSSPs) with narrow pore size distribution were successfully prepared by the ultrasound-assisted sol-gel method using [BRIJO10-MIM]Ts as the template. A shell thickness of up to 300 nm was obtained, and the pore size was expanded from 4.7 to 7.3 nm by adjusting the reaction parameters, overcoming the limitation of pore size to less than 4 nm when using organic alkyl quaternary ammonium or alkyl imidazolium surfactants as the templates. The synthesized 2.7 µm CSSPs were functionalized with tert-butylcarbamoylated quinine and used as an anion exchange chiral stationary phase, exhibiting excellent separation performance for N-substituted amino acid enantiomers.

Antimicrobial Properties and Cytotoxic Effect of Imidazolium Geminis with Tunable Hydrophobicity.

Antimicrobial, membranotropic and cytotoxic properties of dicationic imidazolium surfactants of n-s-n (Im) series with variable length of alkyl group (n = 8, 10, 12, 14, 16) and spacer fragment (s = 2, 3, 4) were explored and compared with monocationic analogues. Their activity against a representative range of Gram-positive and Gram-negative bacteria, and also fungi, is characterized. The relationship between the biological activity and the structural features of these compounds is revealed, with the hydrophobicity emphasized as a key factor. Among dicationic surfactants, decyl derivatives showed highest antimicrobial effect, while for monocationic analogues, the maximum activity is observed in the case of tetradecyl tail. The leading compounds are 2–4 times higher in activity compared to reference antibiotics and prove effective against resistant strains. It has been shown that the antimicrobial effect is not associated with the destruction of the cell membrane, but is due to specific interactions of surfactants and cell components. Importantly, they show strong selectivity for microorganism cells while being of low harm to healthy human cells, with a SI ranging from 30 to 100.

Transgene expression in mice of the Opa1 mitochondrial transmembrane protein through bicontinuous cubic lipoplexes containing gemini imidazolium surfactants

BackgroundLipoplexes are non-viral vectors based on cationic lipids used to deliver DNA into cells, also known as lipofection. The positively charge of the hydrophilic head-group provides the cationic lipids the ability to condensate the negatively charged DNA into structured complexes. The polar head can carry a large variety of chemical groups including amines as well as guanidino or imidazole groups. In particular, gemini cationic lipids consist of two positive polar heads linked by a spacer with different length. As for the hydrophobic aliphatic chains, they can be unsaturated or saturated and are connected to the polar head-groups. Many other chemical components can be included in the formulation of lipoplexes to improve their transfection efficiency, which often relies on their structural features. Varying these components can drastically change the arrangement of DNA molecules within the lamellar, hexagonal or cubic phases that are provided by the lipid matrix. Lipofection is widely used to deliver genetic material in cell culture experiments but the simpler formulations exhibit major drawbacks related to low transfection, low specificity, low circulation half-life and toxicity when scaled up to in vivo experiments.ResultsSo far, we have explored in cell cultures the transfection ability of lipoplexes based on gemini cationic lipids that consist of two C16 alkyl chains and two imidazolium polar head-groups linked with a polyoxyethylene spacer, (C16Im)2(C4O). Here, PEGylated lipids have been introduced to the lipoplex formulation and the transgene expression of the Opa1 mitochondrial transmembrane protein in mice was assessed. The addition of PEG on the surface of the lipid mixed resulted in the formation of Ia3d bicontinuous cubic phases as determined by small angle X-ray scattering. After a single intramuscular administration, the cubic lipoplexes were accumulated in tissues with tight endothelial barriers such as brain, heart, and lungs for at least 48 h. The transgene expression of Opa1 in those organs was identified by western blotting or RNA expression analysis through quantitative polymerase chain reaction.ConclusionsThe expression reported here is sufficient in magnitude, duration and toxicity to consolidate the bicontinuous cubic structures formed by (C16Im)2(C4O)-based lipoplexes as valuable therapeutic agents in the field of gene delivery.Graphical

Photo-responsive graphene oxide liquid crystal hybrid modified with imidazolium surfactant containing azobenzene

ABSTRACT A novel photo-responsive imidazolium surfactant containing azobenzene mesogenic cores (CAzoCM) was designed and synthesised to modify graphene oxide, forming imidazolium surfactant-graphene oxide hybrid (CAzoCM-GO), focusing on the correlation between their mesomorphic behaviour, photo-responsive properties and their chemical structure. CAzoCM and CAzoCM-GO were characterised by FT−IR, Raman spectroscopy and XPS, respectively. The results showed that GO was partially reduced by CAzoCM due to the strong electron effect of the imidazole group. The liquid crystal properties of CAzoCM and CAzoCM-GO were investigated by DSC, POM and variable temperature XRD, respectively. CAzoCM exhibited a smectic A phase as well as the rare smectic C phase and the introduction of GO did not destroy the liquid crystal properties of CAzoCM. Furthermore, the photo-responsive behaviour of CAzoCM and CAzoCM-GO had also been studied by UV-vis spectrum. CAzoCM could be switched from trans to cis isomer in 270 s when it was irradiated under ultraviolet light and from cis to trans isomer in 660 s when it was irradiated under visible light. CAzoCM-GO exhibited more sensitive response behaviour, the photo-responsive time from trans to cis isomerisation became 110 s while the photo-responsive time from cis to trans isomerisation became 195 s.

QSAR modeling for predicting the antifungal activities of gemini imidazolium surfactants against Candida albicans using GA-MLR methods

QSAR modeling for predicting the antifungal activities of gemini imidazolium surfactants against Candida albicans using GA-MLR methods

Reactivity of Inorganic α-Nucleophiles in Acyl Transfer Processes in Water and Surfactant Micelles: III. Systems Based on Dimeric Cationic Imidazolium Surfactants in Alkaline Hydrolysis of Ethyl 4-Nitrophenyl Ethylphosphonate

The kinetics of alkaline hydrolysis of ethyl 4-nitrophenyl ethylphosphonate in micelles formed by cationic dimeric imidazolium surfactants [AlkIm+(CH2)mIm+Alk]·2Br– (where Alk = C16H33–C10H21, m = 2, 3, 4) have been studied. The rate of the reaction in the micellar pseudophase depends on the efficiency of solubilization of the reactants, and the effect of reactant concentrating increases in parallel with the length of the alkyl “tail.” Micellar microenvironment is an important factor responsible for the nucleophilicity of hydroxide ion. The observed acceleration of alkaline hydrolysis of ethyl 4-nitrophenyl ethylphosphonate (micellar catalysis) is primarily related to these two factors. An obvious superiority of dimeric surfactants to monomeric ones is that equal reaction rates are attained at 1–2 orders of magnitude lower concentrations of the former.

The Surface Properties of Solutions of Dicationic Imidazolium Surfactants with Short Bridge Fragments

The pendant drop shape and oscillating pendant drop methods have been employed to study the surface tension and the dilatational rheological surface characteristics at the solution–air interface for aqueous solutions of dicationic imidazolium surfactants with extremely short bridge fragments. A high surface activity has been revealed for these surfactants. High values of the dilatational viscoelasticity modulus have been found for the surfactant solutions. The modulus values increase with a decrease in the length of bridge fragments and an increase in the length of hydrocarbon radicals in surfactant molecules.

Comparative study of cationic liposomes modified with triphenylphosphonium and imidazolium surfactants for mitochondrial delivery

Mitochondria-targeting has become a major tool in the field of cancer treatment. We demonstrate how the positively charged targeting moieties can be exploited to achieve outstanding mitochondria colocalization with a comparative study of n-tetradecyltriphenylphosphonium bromide and 1-(2-hydroxyethyl)-3-tetradecyl-1H-imidazol-3-ium bromide modified liposomes. Herein, for the first time the comparative analysis of liposomes based on 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) noncovalently modified with triphenylphosphonium and imidazolium surfactants with a tetradecyl hydrocarbon tail was performed. The obtained liposomes have high stability (for more than 4 months), a significant positive charge and a high degree of encapsulation efficiency toward rhodamine B and doxorubicin hydrochloride. It was found by the methods of flow cytometry and fluorescence microscopy that modified liposomes loaded with doxorubicin hydrochloride accumulate in large numbers in duodenal adenocarcinoma (HuTu 80) and lung adenocarcinoma (A-549) tumor cells, causing dose-dependent apoptosis. The modified liposomes were loaded with a fluorescent probe rhodamine B for quantitative assessment of their colocalization with mitochondria using confocal microscopy. It was shown that not only the triphenylphosphonium cation is capable of imparting mitochondria-targeting to the nanocontainers, but also the imidazolium cation. These findings may shed additional light on the nature of mitochondria-targeting and provide a whole new ground for the development of novel cation-based mitochondria-targeting moieties.