Synthesis and Characterization of Cationic Surfactants Based on N‐Hexamethylenetetramine as Active Microfouling Agents

Four cationic surfactants of quaternary hexammonium silane chloride based on hexamethylenetetramine and alkyl chloride were synthesized. The chemical structures of the prepared cationic surfactants were elucidated using Fourier transform infrared (FT‐IR) spectroscopy and mass spectrometry analysis. The surface and thermodynamic properties of the prepared surfactants were also studied. The performance of these cationic surfactants as microfouling agents against two strains of Gram‐negative bacteria, namely, Pseudomonas aeruginosa and Escherichia coli, and two strains of Gram‐positive bacteria, namely, Staphylococcus aureus and Bacillus subtilis, were evaluated as antimicrobial agents. The results showed that the maximum antimicrobial activity was detected for N‐hexamethylenetetramine‐N‐ethyl silane ammonium trichloride (Ah). The maximum and minimum antimicrobial activities were 73 and 60 % against S. aureus and E. coli, respectively, at a concentration of 5 mg/l, pH 7, and 37 °C.     

Cholic Acid-Derived Facial Surfactants with Long Side-Chain Quaternary Ammonium: Synthesis and Antimicrobial Activity Study

Four cholic acid cationic surfactants containing a flexible long aliphatic chain were synthesized efficiently. A long aliphatic chain was introduced first on the side-chain carboxyl of cholic acid by one-pot condensation reaction of cholic acid and C12–C18 amines using DCC (Dicyclohexylcarbodiimide) and HOBt (N-hydroxybenzotrizole) as condensation agents for the formation of an amide framework. Then reduction of the amide and quaternization gave a cationic group for strengthening hydrophilicity. This strategy offered a very straightforward and efficient method for access to the designed surfactants in good overall yields. Preliminary results show that an increase both in the length of the hydrophobic tail and in the number of charged groups lowered the CMC of cholic acid-derived cationic surfactants. Cholic acid-based cationic surfactants containing a flexible longer aliphatic chain and a quaternary ammonium had the highest antimicrobial activity.     

Surface-Active Properties and Antimicrobial Study of Conventional Cationic and Synthesized Symmetrical Gemini Surfactants

Symmetrical gemini surfactants of cationic series α,ω-alkanediyl bis (dimethyl ammonium bromide) commonly referred as “m–s–m” have been synthesized. Spectral analysis was performed to confirm compound structures and purity. Conductivity and surface tension measurements provide better understanding of the micellization process. Their self-assembly behavior in aqueous solution is also discussed in detail. The antimicrobial efficacy was measured by bacterial and fungal growth inhibition expressed as minimal inhibitory concentration values against five strains of a representative group of microorganisms viz. Bacillus subtilis, Staphylococcus aureus, Klebsiella pneumonia, Salmonella paratyphi B and Aspergillus niger. All of the synthesized surfactants showed antimicrobial activity against them, but at different levels depending on their structures. The surfactants possessing longer alkyl chains (more hydrophobic environment) demonstrated better antimicrobial functionality. The antimicrobial potency was found to be dependent on the representative target microorganism (Gram-positive bacteria > fungi > Gram-negative bacteria), as well as on the ionic nature of the surfactant (cationic), alkyl chain length (m = 12, 16) and spacer length (s = 2, 4, 6) of the synthesized compounds. Gemini surfactants such as 12-2-12 and 12-4-12 were found to be weakly active whereas 16-2-16 and 16-4-16 compounds proved to be the most potent antimicrobial surface-active agents among the synthesized gemini homologues.     

Surface Parameters and Biological Activity of <Emphasis Type="Italic">N</Emphasis>-(3-(Dimethyl Benzyl Ammonio) Propyl) Alkanamide Chloride Cationic Surfactants

Three cationic surfactants containing amide groups were prepared by quaternization of dimethylaminopropylamine with benzyl chloride. FTIR and ¹H-NMR spectroscopy were used to confirm the chemical structure of the prepared cationic surfactants. The surface parameters were estimated using surface tension measurements at three different temperatures. The prepared cationic surfactant showed a lower CMC than conventional cationic surfactants. Thermodynamic parameters of adsorption and micellization depend mainly of alkyl chain length and temperature. The adsorption process is more favorable than micellization. The biological activity of the three surfactants was estimated using inhibition zone showing that amidoamine cationic surfactants have good activity and the surfactants C12Bn is the most effective one.     

Synthesis and evaluation of micellar properties and antimicrobial activities of imidazole‐based surfactants

The synthesis of two types of imidazole‐based surfactants, [(ROCOCH₂MIm)Br] and [(RNHCOCH₂MIm)Br], of varying chain lengths (C₁₀, C₁₂ and C₁₆), was conducted in the present work. The synthesis involves an initial reaction of bromoacetic acid with fatty alcohols or fatty amines, followed by quaternization with N‐methyl imidazole. The micellar properties of all the synthesized compounds were determined using surface tensiometry and compared with [(RMIm)Br], a well‐studied alkyl‐substituted imidazole‐based surfactant. Within the same homologous series, a decrease in critical micelle concentration (cmc) was observed with increasing alkyl chain length in all three types of cationic surfactants. Introduction of an ester [(ROCOCH₂MIm)Br] or an amide group [(RNHCOCH₂MIm)Br] in the alkyl chain lowers the cmc when compared to a cationic surfactant without functional group, [(RMIm)Br]. The synthesized surfactants were also assayed for antimicrobial activities and found to possess good activities against selected strains.     

Synergism and Phase Behavior of Alcohol Polyoxyethylene Ether Acetate and Cationic Surfactant-Mixed Systems

Synergism in mixed micelle formation and surface tension reduction efficiency and the ternary phase behavior of anionic surfactant (alcohol polyoxyethylene ether acetate containing 10 ethylene oxide group and a fatty chain of C_16–18) with cationic surfactants (dodecyldimethylbenzyl ammonium chloride and lauryltrimethyl ammonium chloride) were investigated. Surface tension of the systems at different molar ratios was studied in detail and the interaction parameters of each system were calculated. The results show that both systems have lower values of critical micelle concentration (CMC) and γ_cmc than individual surfactants especially at equal ratio between cationic and anionic surfactants. Both systems present synergism in mixed micelle formation and surface tension reduction efficiency. The ternary phase behavior of the two systems was investigated using a polarized microscope. The micellar phase and lamellar phase were observed in both systems and the coexisting phase was only observed in the dodecyldimethylbenzyl ammonium chloride system.     

Synthesis,Surface and Antimicrobial Activities of Novel Cationic Gemini Surfactants

A series of novel cationic gemini surfactants [C_nH_2n+1–O–CH₂–CH(OH)–CH₂–N⁺(CH₃)₂–(CH₂)₂]₂·2Br^? [ 3a (n = 12), 3b (n = 14) and 3c (n = 16)] having a 2‐hydroxy‐1,3‐oxypropylene group [?CH₂–CH(OH)–CH₂–O–] in the hydrophobic chain have been synthesized and characterized. Their water solubility, surface activity, foaming properties, and antibacterial activity have been examined. The critical micelle concentration (CMC) values of the novel cationic gemini surfactants are one to two orders of magnitude smaller than those of the corresponding monomeric surfactants. Furthermore, the novel cationic gemini surfactants have better water solubility and surface activity than the comparable [C_nH_2n+1–N⁺(CH₃)₂–(CH₂)₂]₂·2Br^? (n‐4‐n) geminis. The novel cationic gemini surfactants 3a and 3b also exhibit good foaming properties and show good antibacterial and antifungal activities.     

Preparation and properties of a new type of carbohydrate-based cationic surfactant

A new type of cationic surfactant, 6-O-monoesters of 3-(trimethylammonio)propyl d-glucopyranoside, was prepared in high yield by a simple chemoenzymatic synthesis. Surface-active properties of the compounds were found to be highly dependent on the fatty acyl chain length in the 6-O-position with the dodecanoyl and tetradecanoyl esters exhibiting the highest ability to lower surface tension as well as having the lowest critical micelle concentration values. Furthermore, the dodecanoyl ester had excellent foaming properties. The new surfactants also showed antimicrobial activity. Thus, the most potent compound, the dodecanoyl ester, was able to inhibit growth of both bacterial (Gram-positive as well as Gram-negative) and fungal test strains. The antimicrobial effect was somewhat weaker compared to benzalkonium chloride, one of the most frequently used cationics for topical disinfection. However, compared to benzalkonium chloride, the new cationics exhibit a highly improved compatibility with anionic surfactants, as no precipitation took place even in highly concentrated solutions thereby providing a much more robust antimicrobial system. Finally, the new surfactants are expected to be readily biodegradable because they are carbohydrate ester-based.     

Synthesis,Surface-Active Properties,and Antimicrobial Activities of New Neutral and Cationic Trimeric Surfactants

Neutral and cationic series of new trimeric β-hydroxy amino or ammonium surfactants were synthesized via a two-step process involving the Williamson etherification and regioselective oxirane ring opening with primary and tertiary amines, which afforded good to excellent yields. The synthesized compounds were obtained in high purity by a simple purification procedure on column chromatography. The critical micelle concentration (CMC), effectiveness of surface tension reduction (γ _CMC), surface excess concentration (Γ), and area per molecule at the interface (A) were determined and values indicate that the cationic series is characterized by good surface-active and self-aggregation properties. The antimicrobial activities are reported for the first time against representative bacteria and fungi for trimeric compounds. The antimicrobial potency was found to be dependent on the target microorganism (Gram-positive bacteria > fungi > Gram-negative bacteria), as well as both the neutral or ionic nature (cationic > neutral) and alkyl chain length (tri-C₁₂ > tri-C₁₈ > tri-C₈) of the compounds. The tri-C₈ and tri-C₁₈ compounds were found to be almost inactive and the tri-C₁₂ compounds, the most potent antimicrobial surface-active agents from the synthesized series. The trimeric C₁₂ cationic compound was found to be comparable to benzalkonium chloride against Gram-positive bacteria and fungi, in vitro. The antimicrobial effectiveness of this new compound and the facile two-step procedure for synthesizing it with an excellent overall yield (92%) provide a cost effective trimeric gemini surfactant.

Preparation of monodispersed core-shell microspheres with surface antibacterial property employing N-(4-vinylbenzyl)-N,N-diethylamine hydrochloride as surfmer

One-stage synthesis of monodispersed core-shell microspheres by exploratorily introducing a quaternary ammonium cationic surfmer of N-(4-vinylbenzyl)-N,N-diethylamine hydrochloride (VEAH) to emulsion polymerization of styrene (St) is reported. Due to the surface quaternary ammonium moieties and core-shell structure, the resultant PS-co-PVEAH core-shell microspheres have shown antimicrobial activity against Gram-negative bacteria E. coli and Gram-positive bacteria S. aureus. It is found that the quaternary ammonium group of VEAH moieties was the key factor that presented biocidal activity and the antimicrobial activity of the core-shell microspheres shows size dependence and core-shell microspheres with smaller particle size display higher antimicrobial activity.     

Extraction of Rare Earth Metals Using Liquid Surfactant Membranes Prepared by a Synthesized Surfactant

Abstract

Three surfactants, l-glutamic acid dioleyl ester ribitol (nonionic, 2C ₁₈Δ⁹ GE), l-glutamic acid dioleyl ester quaternary ammonium chloride (cationic, 2C ₁₈Δ⁹ GEC ₂ QA), and dioleyl dimethyl quaternary ammonium chloride (cationic, 2C ₁₈Δ⁹ QA) were synthesized for potential use in liquid membrane operations. These surfactants have strongly hydrophobic, twin oleyl chains as the hydrophobic moiety. Using the synthesized surfactants, extraction of rare earth metals was carried out by liquid surfactant membranes in a stirred tank. The extraction behavior of 12 kinds of rare earth metals was systematically studied with 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester (commercial name: PC-88A) as a carrier. Different surfactants having an identical hydrophobic moiety can have significantly different behaviors in rare earth extractions by liquid surfactant membranes, where extraction efficiency appears to be governed by the nature of the interfacial microenvironment between oil and water. An interfacial reaction model which takes into account the adsorption of a surfactant at the interface has been proposed to evaluate the permeation rate of rare earth metals by liquid surfactant membranes. It was found that a cationic surfactant strongly enhances the extraction rate of rare earth metals compared with the conventional surfactant, Span 80. The cationic surfactant 2C ₁₈Δ⁹ GEC ₂ QA appears to be one of the best surfactants currently available for rare earth extraction by liquid surfactant membranes.     

Surface Properties,Thermodynamic Aspects and Antimicrobial Activity of Some Novel Iminium Surfactants

Novel iminium compounds namely p-benzylidene benzyldodecyl iminium chloride (I), p-benzylidene benzylhexadecyl iminium chloride (II), p-benzylidene benzyloctadecyl iminium chloride (III) were prepared and characterized using FTIR, ¹H-NMR and mass spectroscopy. The surface properties such as surface and interfacial tension, and biological activity of these surfactants were investigated. The surface parameters including critical micelle concentration, maximum surface excess, and minimum surface area. Efficiency and effectiveness were calculated, as well as free energies of micellization and adsorption. The prepared cationic surfactants exhibit a better biological activity than the used reference cetyl trimethyl ammonium bromide.     

Antimicrobial and Cytotoxic Properties of Bisquaternary Ammonium Bromides of Different Spacer Length

A group of cationic gemini surfactants (bisquaternary ammonium bromides) with different spacer chain lengths (8–6–8, 8–7–8, 8–8–8, 8–9–8) was investigated, paying special attention to antimicrobial and the cytotoxic properties as well as their antimicrobial activity during long‐term storage. It was shown that the compounds investigated exhibit excellent antimicrobial activity against Gram‐positive bacteria (Staphylococcus aureus) and Gram‐negative bacteria (Pseudomonas aeruginosa) as well as antifungal properties (Candida albicans). The gemini surfactants tested had the differential level of cytotoxicity against normal lymphocytes. It was shown that the spacer chain length plays an important role in antibacterial activity and influences the cytotoxicity. The gemini surfactants with shorter spacer chain length, that had higher critical micelle concentration, showed generally weaker antibacterial properties, but on the other hand, these exhibited lower level of cytotoxicity. Furthermore, the aqueous solution of gemini surfactants exhibited the same antimicrobial activity even after 3 months.     

Corrosion Inhibition by Some Cationic Surfactants in Oil Fields

Two cationic surfactants, namely, tetradecyl dimethyl benzyl ammonium chloride (TDBAC) and tributyl tetradecyl phosphonium chloride (TTPC) were supplied from the local market and characterized. The adsorption tendency of the two surfactants was estimated from the values of the depression of surface tension of the water at the critical micelle concentration. The studied surfactants were evaluated as antimicrobial agents against sulfate-reducing bacteria. These cationic surfactants showed good antimicrobial activities against the tested microorganisms. It was also found that these compounds are good corrosion inhibitors for carbon steel in 0.5?M HCl at doses of 25?C600?ppm.     

Synthesis and Performance of Allyl Dimethyl Dehydroabietyl Ammonium Chloride

Allyl dimethyl dehydroabietyl ammonium chloride (ADMDHA), as a cationic quaternary ammonium polymerizable antibacterial surfactant, was synthesized from dehydroabietylamine and 3‐chloropropene. The structure of ADMDHA was characterized by FT‐IR, NMR, and elemental analysis. The critical micelle concentration (CMC) of ADMDHA and the surface tension at the CMC (γ_CMC) in aqueous solution were about 2.51 × 10^?4 mol L^?1 and 28.5 mN m^?1 at 25 °C, respectively. The emulsion consisting of benzene and water with ADMDHA as an emulsifier maintained its stability for 2 days. Meanwhile, the antimicrobial activities of ADMDHA against Escherichia aerogenes and Pseudomonas aeruginosa were much stronger than those of ampicillin sodium and bromogeramine against the same bacteria.     

Biological Behaviors of Guanidine-Based Cationic Surfactants

The biological properties of novel guanidine‐based cationic surfactant including mono‐alkylguanidine (CnG), N,N,N′‐dimethyl alkylguanidine (CnMG), dicephalic guanidine surfactant (CnGQ), heterogemini guanidine surfactant (diCnGQ) were investigated. Antimicrobial activity was determined via the inhibition of cell viability of the prepared compounds, which was measured against three strains of a representative group of microorganisms. The inhibitions of cell viability were basically about 90 % at the concentration of 25 mg L^?1 to alkyl guanidium salts (CnG, CnMG), and higher than 95 % at a concentration of 10 mg L^?1 to dicephalic guanidine surfactants (CnGQ) and heterogemini guanidine surfactants (diCnGQ). The interactions of bovine serum albumin (BSA) with guanidine surfactants were investigated by fluorescence technology and the effect on BSA conformation follow the order: diC12GQ > C12GQ > C12G > C12MG. At any particular concentration, the biological activity depends on the alkyl chain length to any series of guanidine‐based cationic surfactants.     

Synthesis and Properties of Di‐Chain Esterquat Surfactants

A series of cationic surfactants, di‐chain esterquat surfactants (EQs), were synthesized from N‐methyl diethanolamine, hydrochloric acid, ethylene oxide, and caprylic acid, decylic acid, or lauric acid by a three‐step process. The synthesized surfactants were characterized by IR, MS, and ¹HNMR. Surface properties, antibacterial activity, and biodegradability of the synthesized surfactants were investigated. The results showed that synthesized EQs exhibit high surface activities and good biodegradability. Further, the synthesized surfactant, N,N‐di‐[O‐decanoyl‐2‐hydroxyethyl]‐N‐hydroxyethyl‐N‐methylammonium chloride, exhibits excellent antibacterial activity against E. coli and S. aureus.     

Synthesis of Sulfobetaine-Type Zwitterionic Gemini Surfactants (EAPMAC) and Their Oilfield Application Properties

Four sulfobetaine-type zwitterionic gemini surfactants bis{[(N-ethyl-N alkylamide-ethyl-N-(2-hydr oxyl-3-sodium sulfonic acid) propyl] methylene} ammonium chlorides (EAPMAC-11, EAPMAC-13 EAPMAC-15, and EAPMAC-17) were synthesized by three steps using triethylene tetramine, fatty-acid methyl esters, ethyl chloride, N,N′-dimethyl ethylenediamine, and 3-chloro-2-hydroxypropane sulfonic acid sodium as main raw materials. Their chemical structure was confirmed using Fourier transform infrared spectroscopy (FTIR), 1H-Nuclear Magnetic Resonance (¹H NMR), and elemental analysis. The surface activity, critical micelle concentration, and interfacial activity were correlated with the length of the carbon chain. The results show low emulsifying tendency toward crude oil, low interfical tension, high salt tolerance, and excellent long-term thermal stability. Moreover, high biocidal activities and good protection of metal surfaces against acidic environments are also reflected. These properties suggest that these new gemini surfactants have enormous application potential in oilfield application areas.     

The Aggregation Behavior and Antioxidative Activity of Amphiphilic Surfactants Based on Quinuclidin-3-ol

The self-aggregation and thermodynamic properties of three cationic quaternary ammonium surfactants were investigated. The physicochemical properties of compounds containing quinuclidin-3-ol with even number of carbon atoms (10, 12, and 14) in the hydrophobic tail were measured by conductivity, dynamic light scattering (DLS), and Zeta-potential measurements. DLS and Zeta-potential measurements show a similar size distribution for all surfactants with excellent uniformity, and Zeta-potential increases significantly with increase in the size of hydrocarbon tail. The critical micelle concentration (CMC) and the degree of micelle ionization (β) were determined using conductivity measurements. The CMC values of surfactants were found to be between 3.4 and 23.8 × 10⁻³ M. The standard Gibbs free energy () was derived from conductivity measurements and suggests that surfactants containing longer chains spontaneously form micelles. The antioxidative properties of these cationic surfactants were evaluated using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and oxygen radical absorbance capacity (ORAC) assays. Among the tested samples, N-tetradecyl-3-hydroxyquinuclidinium bromide (QOH-C14) exhibited the highest antioxidative potential (388.30 nmol (TE) equivalents mL⁻¹), which was further investigated by the DNA nicking assay.     

Preparation,surface-active properties,and antimicrobial activities of bis-quaternary ammonium salts from amines and epichlorohydrin

A series of new cationic surfactants, bis-quaternary ammonium salts, were prepared from tert-alkylamine and a product of the reaction of epichlorohydrin with decyl- and dodecylamine, and their surface-active properties were measured. Specifically, the critical micelle concentration (CMC), effectiveness of surface tension reduction (γ_CMC), surface excess concentration (Γ), area per molecule at the interface (A), and standard free energies of adsorption (ΔG _ads ^o) and of micellization (ΔG _mic ^o) were determined. All these surfactants showed good water solubility and low CMC, more than one order of magnitude lower than those of corresponding mono-alkylammonium salts. They also showed good foaming properties but worse wetting capabilities. Many of these compounds had antimicrobial activities against gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis) and yeast (Candida albicans), but they were not active against molds.