Synthesis,Surface and Antimicrobial Activities of Cationic Gemini Surfactants with Semi-Rigid Spacers

Four cationic gemini surfactants featuring semi-rigid spacers were synthesized via a two-step process. The surface-active properties of these surfactants were investigated through surface tension and electrical conductivity measurement. The thermodynamic parameters of micellization were evaluated from electrical conductivity measurements at temperatures ranging from 293 to 313 K. The aggregation behavior of these synthesized gemini surfactants in water were investigated using dynamic light scattering and transmission electron microscopy. Further, the antimicrobial activities of these synthesized gemini surfactants against both Gram-positive and Gram-negative bacteria were also investigated.     

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.     

Synthesis,Surface Property and Antimicrobial Activity of Cationic Gemini Surfactants Containing Adamantane and Amide Groups

A series of novel cationic gemini surfactants, namely 1,3-adamantanedicarboxylic acid bis(alkyldimethyl-3-ammoniopropyl amide) dibromide designated as [Ad-2(amC _n )] (n = 12, 14, 16), containing adamantane, two amide groups, and two hydrocarbon chains, were synthesized from 1,3-adamantanedicarboxylic acid. The surface-active properties of the surfactants were investigated through surface tension and electrical conductivity measurement. A series of thermodynamic parameters such as standard free energy \(\left( {\Delta G^\circ_{\text{m}} } \right)\) , enthalpy \(\left( {\Delta H^\circ_{\text{m}} } \right)\) , and entropy \(\left( {\Delta S^\circ_{\text{m}} } \right)\) of micellization were evaluated from electrical conductivity measurements in the temperature range from 288 to 308 K. The micellization for [Ad-2(amC _n )] is entropy-driven at low temperature and enthalpy-driven at high temperature. Further, the antimicrobial activity of the synthesized gemini surfactants against both Gram-positive and Gram-negative bacteria was also investigated, and this study showed that the compound [Ad-2(amC₁₂)] has excellent antibacterial activity against all studied bacteria.     

Synthesis and Surface Properties of Novel Gemini Imidazolium Surfactants

Five new Gemini imidazolium surfactants were synthesized from imidazole and 1-bromoalkane (C₈, C₁₀, C₁₂, C₁₄, C₁₆) to get 1-alkylimidazole, which was further reacted with 1,3-dichloropropan-2-ol to form the surfactant molecule, 1,1′-(propane-1,3-diyl-2-ol) bis(3-alkyl-1H-imidazol-3-ium) chloride. The structures of the five new surfactants and intermediates were characterized by ¹H-NMR, ¹³C-NMR and IR spectra. Thermal properties of the five new surfactants were studied with thermogravimetric analysis and differential scanning calorimetry, the five new surfactants showed a transition from a crystalline phase to a thermotropic liquid–crystalline phase at around ca. 100 °C, which transformed to an isotropic liquid phase at around ca. 165 °C. The five new surfactants critical micelle concentrations (CMC) in the aqueous solutions were determined by surface tension and electrical conductivity methods. The surface tension measurements provided a series of parameters, including critical micelle concentration (CMC), surface tension at the CMC (γ _CMC), adsorption efficiency  (pC ₂₀), and effectiveness of surface tension reduction (π_CMC). In addition, with application of the Gibbs adsorption isotherm, maximum surface excess concentration (Γ_max) and minimum surface area/molecule (A_min) at the air–water interface were obtained. The parameters β (degree of counterion binding to micelles), ΔG _ads ^θ (Gibbs free energy of adsorption), and ΔG _mic ^θ (Gibbs free energy change of micellization) were also derived. The results indicated that the five new Gemini surfactants exhibited very low CMC and a good efficiency in lowering the surface tension of water. The foamability and foam stability of the five new surfactants were also examined at different CMC.     

Synthesis and Properties of Novel Phenylenediamine Gemini Surfactants

In the present work, a two-step method was adopted to synthesize a series of novel Gemini surfactants using N,N-dimethylalkyl amines (alkyl length = C₁₂, C₁₆ and C₁₈), epichlorohydrin, and n-phenyllenediamine as starting materials. The products were characterized using mass spectroscopy (MS) and nuclear magnetic resonance spectroscopy (¹H NMR). Systematic experiments were conducted to evaluate their surface activity, foaming properties, and antibacterial performance. Results showed the critical micelle concentrations (CMC) of the C₁₂-based, C₁₆-based, and C₁₈-based phenylenediamine surfactants were 3.295 × 10⁻³, 2.532 × 10⁻⁴, and 3.140 × 10⁻⁴ mol L⁻¹ at 298 K, respectively, with corresponding surface tension (γ_cmc) values of 28.24, 31.95, and 35.06 mN m⁻¹ under the same conditions. The Gemini surfactants showed not only good surface activity and foaming properties, but also demonstrated good antimicrobial performance against Gram-positive and Gram-negative bacteria and fungi.     

Synthesis,Surface Activity,and Antimicrobial Efficacy of Hydrogenated Cardanol-Derived Positively Charged Asymmetric Gemini Surfactants

Nine different hydrogenated cardanol-based quaternary ammonium compounds including one conventional single-tale single-head surfactant, one bicephalic single-tale double-head surfactant, and seven asymmetric Gemini surfactants were synthetized using a simple process with high yields. Their structures were characterized using ¹H NMR, ¹³C NMR, and high-resolution mass spectral studies. Their surface active properties were evaluated by the wilhelmy plate method at 25 °C and physical parameters like CMC, γ_CMC, π_CMC, C₂₀, τ_CMC, and A_min were calculated. The Krafft temperature values of C-BP-1, C-BP-4, and C-BP-6 are lower than 0 °C, suggesting high-potential industrial application. All synthesized compounds but C-BP-F exhibit great antimicrobial ability against Gram-positive bacteria (S. aureus [ATCC 25923] and C. glutamicum [ATCC 13032]) while inadequate antimicrobial ability against Gram negative strains (E. coli [ATCC 25922] and P. aeruginosa [ATCC 27853]).     

Preparation of a Novel Class of Cationic Gemini Imidazolium Surfactants Containing Amide Groups as the Spacer: Their Surface Properties and Antimicrobial Activity

A class of novel cationic Gemini imidazolium surfactants containing amide groups as the spacer were synthesized from ethylenediamine and 1-bromoalkane(C₈, C₁₀, C₁₂, C₁₄, C₁₆) by N-alkylation to get N,N′-dialkyl ethylenediamine (1a–e), 1a–e was further reacted with chloroacetyl chloride by N-acylation to get N,N′-(ethane-1,2-diyl)bis(2-chloro-N-alkylacetamide) (2a–e), which was further reacted respectively with 1-methyl imidazole by quaternized to form the surfactant molecule, N,N′-((ethane-1,2-diyl)bis(alkyl-azanediyl)bis(2-oxoethane-2,1-diyl)) bis(1-methyl-1H-imidazol-3-ium) dichloride. The structures of intermediates (1a–e) and (2a–e) were characterized by IR and ¹H NMR. The structures of the surfactants (3a–e) were characterized by IR, ¹H-NMR and ¹³C-NMR and element analysis. The critical micelle concentrations (CMC) of 3a–e were determined by the conductivity method at 25 °C. The CMC values decreased with increasing the length of the hydrophobic chain. The surfactants (3a–e) showed good foaming stability, emulsion ability and wetting ability. The surfactants (3a–e) also have good antimicrobial activity against Staphylococcus aureus, Escherichia coli and Bacillus subtilis.     

Synthesis and Properties of Dicephalic Cationic Surfactants Containing a Quaternary Ammonium and a Guanidine Group

Novel dicephalic surfactants containing a quaternary ammonium and a guanidine group were synthesized, and the effect of the alkyl chain length on micellization and antimicrobial activity were investigated. Surface tension and conductivity were applied to study the self-aggregation of the amphiphilic molecule in aqueous solution. The results indicated that these compounds reduce the surface tension to a level of 30–36 mN/m at the air/water interface and that there is a characteristic chain length dependence of the micellization process of surfactants. The antimicrobial activity was evaluated against Gram-negative, Gram-positive bacteria and fungi, indicating strong antibacterial activity against tested strains.     

Novel Gemini Cationic Surfactants: Thermodynamic,Antimicrobial Susceptibility,and Corrosion Inhibition Behavior against Acidithiobacillus ferrooxidans

The Egyptian oil and gas industry is suffering from severe metal corrosion problems, particularly microbial-induced corrosion. There is limited knowledge on the corrosion inhibition of carbon steels in the presence of an acidophilic, iron-oxidizing bacterial species Acidithiobacillus ferrooxidans. Therefore, in this study, novel Gemini cationic surfactants, in three forms depending on variation in alkyl chains of 8, 12, and 16 carbon atoms named FHPAO, FHPAD, and FHPAH, respectively, were synthesized and characterized by Fourier transform infrared and nuclear magnetic resonance spectroscopy. The surface parameters and the thermodynamic of the synthesized surfactants were evaluated at three different temperatures, 20, 40, and 60 °C. The synthesized Gemini cationic surfactants were tested as broad-spectrum antimicrobial, antibacterial and anticandida agents. They evaluated as biocides and corrosion inhibitors against Acidithiobacillus ferrooxidans. FHPAD showed higher adsorption ability at the solution interface and higher affinity to construct micelles than FHPAO and FHPAH. Both adsorption and micellization processes were hydrophobic and temperature dependent. FHPAO, FHPAD and FHPAH exhibited wide-spectrum antimicrobial activities, and the highest activity and the lowest minimum bactericidal/fungicidal inhibitory concentrations were attributed to FHPAD. Furthermore, synthesized FHPAD demonstrated the highest metal corrosion inhibition efficiency of 95.5% at 5 mM in comparison to 87.5% and 81.7% for FHPAO and FHPAH, respectively. In conclusion, this study provides novel synthesized cationic surfactants with many applications in the oil and gas industry, such as broad-spectrum antimicrobial, biocides, and corrosion inhibitors for acidophilic, iron-oxidizing bacterial species Acidithiobacillus ferrooxidans.     

Gemini Cationic Surfactants: Synthesis and Influence of Chemical Structure on the Surface Activity

Three cationic gemini surfactants were synthesized and characterized using different methods. Their surface activities were measured using surface and interfacial tension measurements. The effect of the spacer chain length on the surface activity, emulsification power and interfacial tension was studied. The thermodynamic parameters showed the tendency towards micellization and adsorption. The results showed that longer spacers increased the micellization tendencies of the surfactants, while shorter spacers increased the adsorption tendency at the air–water interface.     

Synthesis,Surface Activity,Thermodynamic Parameters,and Performance Evaluation of Branched Carboxylate Gemini Surfactants

Three novel carboxylate gemini surfactants (3C_ntaDA, n = 8, 10, and 12) were synthesized by two simple steps, and their structures were characterized using FT-IR and ¹H NMR. The surface activities of these surfactants were obtained from surface tension measurements at different temperatures, and the surface parameters containing the critical micelle concentration (CMC), surface tension (γ), minimum surface area per molecule ( A_min ), and maximum surface excess concentration ( Γ_max ) were obtained from surface tension measurements. The experimental results show that 3C_ntaDA surfactants have higher surface activities compared with the corresponding conventional surfactants. The thermodynamic parameters of the micellization process were investigated, and the calculated results show that it was an exothermic and spontaneous process. The emulsification and foam performance of these surfactants were also evaluated at different concentrations at 298.15 K.     

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.

乙二胺四乙酸合成双子型阳离子表面活性剂

以乙二胺四乙酸、环氧氯丙烷和十二烷基-N,N-二甲基叔胺为原料合成双子（Gemini）型阳离子表面活性剂乙二胺四乙酸四酯季胺盐。研究了两种合成方法：一是乙二胺四乙酸先与环氧氯丙烷反应,生成的酯化产物再和十二烷基-N,N-二甲基叔胺反应生成产物乙二胺四乙酸四酯季胺盐;二是先将乙二胺四乙酸加入十二烷基-N,N-二甲基叔胺中,进行Lewis酸碱反应,乙二胺四乙酸负离子与产生的季铵盐结合为离子对,再加入环氧氯丙烷从而生成产物乙二胺四乙酸四酯季胺盐。研究了乙二胺四乙酸与环氧氯丙烷的摩尔比对合成过程及产物性能的影响,并测试了相关性能。产品显示了良好的发泡性和稳定性。     

Synthesis and Thermodynamic Properties of Rosin-Based Cationic Gemini Surfactants

A series of rosin-based cationic gemini surfactants with different spacer length (n = 2, 3, 4) were synthesized and characterized. Surface activity and micellization parameters including the critical micelle concentration, the degree of counterion dissociation, and thermodynamic functions of micellization in aqueous solutions have been investigated. Free energy perturbation was performed to study the enthalpy-entropy compensation of the synthesized gemini surfactants in aqueous solutions. The experimental results showed that the micellization of rosin-based gemini surfactants in aqueous solutions is a spontaneous and entropy-driven process. The micellization process was found to follow the entropy–enthalpy compensation phenomenon.     

Microwave-Assisted Synthesis and Properties of a Novel Cationic Gemini Surfactant with the Hydrophenanthrene Structure

A novel cationic gemini surfactant with the hydrophenanthrene structure has been synthesized from dehydroabietic acid by use of conventional thermal conditions and microwave irradiation. Its structure was confirmed by IR, ¹H NMR, and ¹³C NMR spectroscopy. It was found that microwave-assisted synthesis is an efficient means of preparation of this cationic gemini surfactant, with shorter reaction times and higher yields. The title compound had high surface activity. The CMC was 3.1 × 10⁻⁵ mol L⁻¹, γ _CMC was 26.3 mN m⁻¹, and emulsifying power (with benzene) reached five days. Comparison of this gemini surfactant and its monomeric counterpart proved the gemini surfactant was more surface active.

Amido-Amine-Based Cationic Gemini Surfactants: Thermal and Interfacial Properties and Interactions with Cationic Polyacrylamide

Experimental studies were conducted to investigate thermal and interfacial properties of two in‐house synthesized amido‐amine‐based cationic gemini surfactants namely: dodecanoic acid [3‐({4‐[(3‐dodecanoylamino‐propyl)‐dimethyl‐amino]‐butyl}‐dimethyl‐amino)‐propyl]‐amide dibromide ( 12‐4‐12 ) and dodecanoic acid [3‐({6‐[(3‐dodecanoylamino‐propyl)‐dimethyl‐amino]‐hexyl}‐dimethyl‐amino)‐propyl]‐amide dibromide ( 12‐6‐12 ). Thermogravimetric analysis showed the excellent thermal stability of surfactants and no structural degradation was observed at temperatures up to 250 °C. The long‐term thermal stability of the surfactants was investigated with the aid of spectroscopic techniques such as nuclear magnetic resonance (NMR (¹H and ¹³C) and Fourier transform infrared (FTIR) spectroscopy. Both surfactants were found to be thermally stable, and no changes in structure were observed after aging for 10 days at 90 °C. The interfacial tension of the surfactants was measured at three different temperatures (30, 60, and 80 °C), and the results showed a decrease in interfacial tension with increasing temperature and increasing spacer length of the surfactants. Rheological measurements were used to assess the interactions between the cationic gemini surfactant and cationic polyacrylamide. The addition of cationic surfactant reduced the viscosity and storage modulus of the polymer at low shear rate and frequency due to surfactant–polymer interactions and charge screening. The investigated surfactant–polymer system has great potential in high‐temperature carbonate reservoirs, where conventional anionic surfactants are not recommended due to high adsorption.     

Synthesis,Surface Activity and Aggregation Behavior of Novel Gemini Pyridinium Amphiphiles

A series of novel pyridinium cationic gemini amphiphiles, 3,3′-(carbonyldiimino)bis (1-n-alkylpyridinium) dibromides, having octyl, decyl, dodecyl, tetradecyl alkyl chains were synthesized. The surface properties and aggregation behavior in aqueous solution were evaluated by surface tension, dynamic light scattering (DLS), and transmission electron microscopy (TEM) measurement. The adsorption at the air/solution interface of all the compounds were quantitative described using the Frumkin model, and the effect of alkyl chain length on surface activity and aggregate behavior was analyzed. It was found that all the gemini amphiphiles possess surface activity and low critical micellization concentration (CMC) values. The values of log CMC depended linearly on the carbon number of the alkyl chains, but the surface tension at the CMC (γ_cmc) showed a minimum for the compound with dodecyl chains. Combinations of DLS and TEM observations showed the existence of vesicles with a broad size distribution in aqueous solution. Meanwhile, vesicles formed below the CMC could be a possible reason for the observed deviation of surface tension curves from the Frumkin model.     

Synthesis and Performance of a Multi-Purpose Gemini Precursor and the Derivative Alkylaryl Sulfonate Gemini Surfactants

The phenol–formaldehyde condensation reaction to synthesize a gemini precursor was renewed by using high efficient and environmentally benign resin catalysts instead of protonic acids, and the conversion, yield and selectivity of the reaction were all upgraded from the 60 % by the traditional way to over 90 % by the new way. Three alkylaryl sulfonate gemini surfactants were derived from the above gemini precursor by O-methylation, sulfonation and neutralization, that is, sodium salt of sulfonated bis(2-hydroxy-5-nonylphenyl)methane (SBHNM), sodium salt of sulfonated bis(2-hydroxy-5-dodecylphenyl)methane (SBHDM) and sodium salt of sulfonated bis(2-methoxy-5-nonylphenyl)methane (SBMNM). And their performances in aqueous solution were further investigated. The results show that the three gemini surfactants exhibit higher effectiveness and efficiency in surface tension reduction than a monomeric reference surfactant sodium dodecylbenzene sulfonate (SDBS). Furthermore their critical micelle concentration values are at least one order of magnitude lower than that of SDBS. It is also shown that O-methylation of the hydroxyl group in the gemini precursor is effective at improving the surface activity of the gemini surfactants, such as efficiency in surface tension reduction, foam stability and calcium stability. It is suggested that the synthesized hydrophobic skeleton could be a multi-purpose gemini precursor from which various gemini surfactants could be derived by further hydrophobic or hydrophilic modification.     

十二烷基多季铵盐Gemini型阳离子表面活性剂合成

控制反应物乙二胺与环氧氯丙烷的配比，得到乙二胺与环氧氯丙烷的摩尔比分别为1：5、1：4、1：1的产物。然后与自制十二烷基二甲胺进一步反应温度60℃；反应时间1h：反应溶剂、水和乙醇的混合溶剂。通过测定不同浓度下溶液的表面张力，得到其产物I、Ⅱ的临界胶束浓度为0.05%（质量百分比）左右。说明产品具有很低的临界胶束浓度和较好的表面活性。进一步的实验证明；合成产物具有较好的发泡力、稳泡力和金属腐蚀的抑制性能，并考察了其与阴离子表面活性剂的复配性能。     

Surface and Biological Activity of Some Novel Cationic Surfactants

In this study, steps were taken toward the development of bactericidal and fungicidal synthetic cationic surfactants by reacting decyl, dodecyl or tetradecyl amine with acetic or hydrochloric acid to produce a series of amine salts which consequently converted to copper or cobalt cationic complexes via complexing the first series compounds with copper (II) or cobalt (II) ions. Surface properties such as interfacial tension and emulsifying power of these surfactants were investigated. The surface parameters including critical micelle concentration (CMC), maximum surface excess (Γ_max) and minimum surface area (A _min) were studied. Free energy of micellization (ΔG°_mic) and adsorption (ΔG°_ads) were calculated. The antimicrobial activity was determined via the inhibition zone diameter of the prepared compounds, which measured against five strains of a representative group of microorganisms. FTIR spectra, elemental analysis and H¹ NMR spectrum were performed to confirm compound structure and purity.