Quaternary Ammonium Gemini Surfactants Research Articles

Synthesis and dilute aqueous solution properties of ester functionalized cationic gemini surfactants having different ethylene oxide units as spacer

New series of ester functionalized quaternary ammonium gemini surfactants having different ethylene oxide units as spacer have been synthesized and investigated for their aggregation behavior and thermodynamic properties of micellization by surface tension, conductivity, and fluorescence methods. The critical micelle concentration (cmc) of these gemini surfactants increases with the increase in the length of polar hydrophilic ethylene oxide spacer. The micellization process has been found to be entropy-driven and dependent on both the tendency of the hydrophobic group of the surfactants to transfer from aqueous environment to interior of micelle as well as the rearrangement of flexible ester-linked ethylene oxide units (hydrophilic spacer) into aqueous phase. The polar ester functional groups and pairs of nonbonding electrons on oxygen atom of ethylene oxide spacer form hydrogen bonding with water molecules enhancing their solubility in aqueous system.

Phase-transfer catalysis of a new cationic gemini surfactant with ester groups for nucleophilic substitution reaction

Abstract A highly effective phase transfer of a quaternary ammonium gemini surfactant with ester groups ((diethylhexanedioate) diyl-α,ω-bis(dimethyl dodecyl ammonium bromide) referred to as 12-10-12) was synthesized with high yield and characterized by infrared spectroscopy, elemental analysis and 1H-NMR. Then, 12-10-12 was used as a phase transfer catalyst to study the catalytic effect on the reaction of anhydrous sodium acetate and 4-methylbenzyl chloride. The possible catalytic mechanism and the influence of surfactant concentration, temperature and type are also discussed. The experimental results showed that the catalysis efficiency was more active than the traditional, single-chained surfactant, tetrabutyl ammonium bromide. It also revealed that the reaction was first-order with respect to the concentration of 4-methylbenzyl chloride. The concentration of 4-methylbenzyl chloride grew linearly with the concentration of 12-10-12 and as the reaction temperature increased. The optimum reaction time was 7 h.

Interfacial Tensions for System of n-Heptane + Water with Quaternary Ammonium Surfactants and Additives of NaCl or C2–C4 Alcohols

Interfacial tensions of the oil–water interface versus surfactant concentration for n-heptane + water system with each of six single chain quaternary ammonium surfactants, and six Gemini quaternary ammonium surfactants around their critical micelle concentrations (CMC) have been measured by using the spinning drop method. The influences of additives (NaCl, ethanol, n-propanol, and n-butanol) on the interfacial tensions have also been investigated. It is observed that all of the surfactants can significantly lower the interfacial tensions of the n-heptane + water system. The required concentrations to reach the lowest interfacial tensions for Gemini surfactants with C12 and C14 alkyl chains are less than 10 % of those values for the corresponding single chain surfactants. For the n-heptane + water + Gemini surfactant systems, the addition of NaCl can lower the required surfactant concentrations to obtain the lowest interfacial tensions; however, the addition of C2–C4 alcohols has no evident effects but leads to a slight decrease of the values of these interfacial tensions.

Phase Transition of a Quaternary Ammonium Gemini Surfactant Induced by Minor Structural Changes of Protic Ionic Liquids

The aggregation behaviors of a Gemini surfactant [C12H25(CH3)2N(+)(CH2)2N(+)(CH3)2C12H25]Br2(-) (12-2-12) in two protic ionic liquids (PILs), propylammonium nitrate (PAN) and butylammonium nitrate (BAN), were investigated by means of several experimental techniques including small and wide-angle X-ray scattering, the polarized optical microscopy and the rheological measurement. Compared to those in ethylammonium nitrate (EAN), the minor structural changes with only one or two methylene units (-CH2-) increase in cationic chain length of PIL, result in a dramatic phase transition of formed aggregates. The critical micellization concentration was increased in PAN, while no micelle formation was detected in BAN. A normal hexagonal phase was observed in the 12-2-12/PAN system, while the normal hexagonal, bicontinuous cubic, and lamellar phases were mapped in the 12-2-12/BAN system. Such aggregation behavior changes can be ascribed to the weaker solvophobic interactions of 12-2-12 in PAN and BAN. The unique molecular structure of 12-2-12 is also an important factor to highlight such a dramatic phase transition due to the PIL structure change.

Synthesis of a Novel Class of Organosilicon Quaternary Ammonium Gemini Surfactants

A novel class of organosilicon quaternary gemini surfactants alkanediyl-α, ω-bis(methyl-dimethoxy-silopropyl-diethyl ammonium bromide) was synthesized with N,N-diethyl-aminopropyl-methyl-dimethoxysilane and α, ω-dibromoalkane as the raw materials, where the N,N-diethyl-aminopropyl-methyl-dimethoxysilane was synthesized by reacting diethylamine with γ-chloropropylmethyldimethoxysilane. The effects of various solvents on the conversion rate of the reaction and on purification of surfactants were investigated. The structures of the organosilicon quaternary ammonium gemini surfactants were determined by means of 1H NMR and elemental analysis. The properties of aqueous solution were measured with electrical conductivity and viscosity methods.

Effects of Structure Dissymmetry on Aggregation Behaviors of Quaternary Ammonium Gemini Surfactants in a Protic Ionic Liquid EAN

The aggregation behaviors of a series of dissymmetric cationic Gemini surfactants, [C(m)H(2m+1)(CH(3))(2)N(CH(2))(2)N(CH(3))(2)C(n)H(2n+1)]Br(2), designated as m-2-n (with a fixed m + n = 24, m = 16, 14, 12) have been investigated in a protic ionic liquid, ethylammonium nitrate (EAN). Surface tension, polarized optical microscopy (POM), small-angle X-ray scattering (SAXS), and rheological measurements are adopted to investigate the micellization and lyotropic liquid crystal (LLC) formation. The obtained results indicate that the structure dissymmetry plays an important role in aggregation process of m-2-n. With increasing degree of dissymmetry, the critical micellization concentration, the maximum reduction of solvent surface tension, and the minimum area occupied per surfactant molecule at the air/EAN interface all become smaller. The thermostability of formed LLCs is therefore improved because of the more compact molecules. These characteristics can be explained by the enhancement of solvophobic effect due to the increased structure dissymmetry of Gemini surfactants.

Interactions of bovine serum albumin with cationic imidazolium and quaternary ammonium gemini surfactants: Effects of surfactant architecture

The interactions of BSA with a series of cationic imidazolium gemini surfactants ([Cn-s-Cnim]Br2, n=10, 12, 14, s=2, 4, 6), quaternary ammonium surfactants (C12C2C12), and their corresponding monomers ([C12mim]Br and DTAB) are investigated by fluorescence using pyrene as a molecular probe, synchronous fluorescence, circular dichroism (CD), and UV–visible absorption spectra. These surfactants are used to elucidate the effects of surfactant hydrophilic head group, spacer length, and hydrophobic chain length on the conformation of BSA. The results of fluorescence spectra and CD show that the imidazolium gemini surfactants with shorter spacers or with longer hydrophobic chains have a larger effect on BSA unfolding, and the imidazolium gemini surfactant interacts with BSA more strongly than its corresponding monomer and the quaternary ammonium gemini surfactant. These conclusions have been confirmed by the binding constants (Ka) and binding sites (n) for the BSA/surfactant system. Stern–Volmer quenching constants KSV of cationic surfactants binding to BSA are obtained, indicating that the probable quenching mechanism is initiated by ground-state complex formation rather than by dynamic collision. Moreover, the synchronous fluorescence spectra show that the surfactants mainly interact with tryptophan residues of BSA.

Synthesis, Optical and Surface Properties of the New Gemini Quaternary Ammonium Surfactants Containing DSD Acid-triazine Structure

Four novel gemini quaternary ammonium surfactants containing DSD acid-triazine structure were synthesized using a facile three-step synthetic route , from 4,4'-diamino-2,2'-disulfonic-stilbene (DSD acid), cyanuric chloride and dimethyl dodecylamine. The structures and optical properties of compounds (6a-d) were characterized by Fourier-Transform infrared (FT-IR) spectroscopy, UV-visible absorption spectra and fluorescence emission spectrum. The surface tension and the Critical Micelle Concentration (CMC) were evaluated. The result shows that the four compounds at lower concentrations can greatly reduce the surface tension of aqueous solutions. The spectroscopic properties of these quaternary ammonium salts are assessed for their effectiveness and potential as fluorescent brightening agents.

Novel ionic liquid-type Gemini surfactants: Synthesis, surface property and antimicrobial activity

Novel quaternary ammonium Gemini surfactants, which turned out to be ionic liquids due to the intermolecular hydrogen bonding formed from hydroxyl groups in the spacers, were synthesized and characterized by IR, 1H NMR, 13C NMR and mass spectra. The surface properties of the Gemini surfactants were investigated by means of surface tension measurements. Surface tension parameters including surface excess concentration, Г cmc, surface area demand per molecule, A cmc, efficiency in surface tension reduction, pC 20, the effectiveness of surface tension reduction, γ cmc, critical micelle concentration, CMC, and standard free energy of micellization, Δ G a d s 0 and Δ G m i c 0 were obtained. The results indicated that compared with those of their corresponding conventional single-chain surfactant counterparts, these novel Gemini surfactants exhibited lower CMC values and greater efficiency in lowering the surface tension of water. The foamability and foam stability of these Gemini surfactants decreased with the increase in the length of the spacer chain. Gemini surfactants with alkyl chains of moderate length (C 12 or C 14) showed the best foamability and the highest foam stability. Some of the Gemini surfactants exhibited antimicrobial activity against Gram-negative bacteria Escherichia coli.

Tandem mass spectrometric analysis of novel diquaternary ammonium gemini surfactants and their bromide adducts in electrospray‐positive ion mode ionization

Gemini surfactants are cationic lipids which are utilized for both in vitro and in vivo gene delivery. Structurally, they are comprised of two hydrophobic tail regions with polar head termini that are attached to one another through a spacer region. Structural elucidation and characterization of 29 novel diquaternary ammonium gemini surfactant molecules were achieved using a quadrupole time-of-flight mass spectrometer (QqToF-MS) and a quadrupole-hexapole-quadrupole mass spectrometer (QhQ-MS). The tested compounds were categorized into four distinct structural families based upon the composition of the spacer region. Single stage (MS), tandem stage (MS/MS) and quasimulti-stage (quasi MS(3)) mass spectrometric analysis allowed for confirmation of each gemini surfactant's molecular composition and structure through the identification of common and unique product ions. Identification of similarities in the gemini surfactants' fragmentation behaviour resulted in the production of a universal fragmentation pathway that can assist in the future MS/MS analysis of novel quaternary ammonium gemini surfactants, with unique product ions being indicative of specific structural elements. Furthermore, evidence for the association of agemini surfactant with bromine counter ion was confirmed during MS analysis of tested gemini surfactants regardless of their chemical composition; previously, evidence for bromine and gemini surfactant association was only observed with compounds bearing short alkyl spacer regions. MS/MS analysis of the bromine adducts was also confirmatory to the molecular structure.Understanding the ionization and fragmentation behaviour of gemini surfactants, including bromine adducts, will allow for future qualitative and quantitative identification of these novel drug delivery agents within biological samples.

Interfacial dilational viscoelasticity and foam stability in quaternary ammonium gemini surfactant systems: influence of intermolecular hydrogen bonding

This paper reports the adsorption and interfacial viscoelasticity of gemini surfactants with a hydroxyl-substituted spacer, 2-hydroxyl-propanediyl-α,ω-bis(dimethyldodecylammonium bromide), 2-hydroxyl-butanediyl-α,ω-bis(dimethyldodecylammonium bromide), and 2,3-hydroxyl-butanediyl-α,ω-bis(dimethyldodecylammonium bromide), referred to as 12-3(OH)-12, 12-4(OH)-12, and 12-4(OH)2-12, respectively, at the air/water interface using dropping shape and interface dilational rheology measurements. For comparison, the unsubstituted surfactants were also examined at identical conditions. The results showed that substituted surfactants produced a remarkably higher interfacial elasticity than the corresponding unsubstituted ones. This was attributed to the effect of the intermolecular hydrogen bonding occurring between the hydroxyl-substituted spacers of adsorbed molecules, which resulted in tighter packing of the molecules in the monolayer. Besides, we measured foam stability. The foam produced by the substituted geminis was found to have higher stability than that by the unsubstituted geminis. It was suggested that the foam stability may be related to the limit elasticity of interfacial film at the level of identical surface excesses.

Effect of alkyl tail length of quaternary ammonium gemini surfactants on foaming properties

This paper reports the investigation about the effect of the alkyl tail length of quaternary gemini surfactants, 2-hydroxyl-propanediyl-α,ω-bis(dimethylalkylammonium bromide), referred to as m-3(OH)- m, where m represents the number of carbon atoms at each alkyl tail, on the foamability and foam stability. To understand the foaming behavior, the adsorption of surfactants at the air/water interface as well as the dilational viscoelasticity of their films was studied using surface tension and dilational interfacial rheology measurements. 14-3(OH)-14 was found to have stronger foamability and stabilize more efficiently the foam than 12-3(OH)-12, however, 16-3(OH)-16 failed to generate foam. The latter was attributed to the self-coiling of the long hexadecyl tails prior to the adsorption of surfactant at the air/water interface, resulting in the ageing effect of the adsorption behavior. For both 12-3(OH)-12 and 14-3(OH)-14, the results revealed a good correlation between the high limit interfacial elasticity and high stability of foam at the level of identical surface excesses.

Adsorption and corrosion inhibitive properties of gemini surfactants in the series of hexanediyl-1,6-bis-(diethyl alkyl ammonium bromide) on aluminium in hydrochloric acid solution

Four new quaternary ammonium gemini surfactants in the series of hexanediyl-1,6-bis-(diethyl alkyl ammonium bromide), referred as C m C 6C m (Et)·2Br ( m = 10, 12, 14, 16), were synthesized and tested as corrosion inhibitors of aluminium in 1 mol/L HCl solution at 25 °C using gravimetric, gasometric measurements and SEM techniques. Results obtained show that the surfactants studied are efficient corrosion inhibitors for aluminium in hydrochloric acid solution. The inhibition efficiencies of C m C 6C m (Et)·2Br increase with the surfactant concentrations, and the good inhibiton efficiencies are reached near their critical micelle concentrations. In addition, the inhibition efficiency for aluminium slightly increases with increasing surfactant chain length ( m) at the same concentration since the adsorption capacity of C m C 6C m (Et)·2Br is increased with m. These gemini surfactant inhibitors adsorb at the aluminium/solution interface according the Langmuir adsorption isotherm. Thermodynamic parameters of adsorption ( b, Δ G ads) of C m C 6C m (Et)·2Br were determined and the inhibition mechanism has been discussed. The adsorption of gemini surfactants C m C 6C m (Et)·2Br at the aluminium/solution interface can be considered as a cooperative adsorption and the high absolute values of Δ G ads could be attributed to the high adsorption ability of the gemini surfactant molecules on the aluminium surface, forming a strong protective film by the synergistic effect between bromide anions and positive quaternary ammonium ions. On the basis of the variation of surface coverage rates ( θ) with the surfactant concentrations, the adsorption modes of the gemini surfactants C m C 6C m (Et)·2Br at the aluminium/solution interface were proposed.

Synthesis of Mesoporous Tungsten Trioxide with Crystalline Pore Wall at Low Hydrothermal Temperature

Well-ordered hexagonal mesoporous tungsten trioxide with crystalline pore walls were synthesized at low hydrothermal temperature by using cationic quaternary ammonium gemini surfactants as structure-directing agents and sodium tungstate dihydrate (Na2WO4·2H2O) as a precursor. The effects of alkyl chain length of gemini surfactants, hydrothermal temperature and molar ratio of tungsten to gemini surfactants have been investigated in detail. The strong self-assembly ability of gemini surfactants, strong electrical interaction between gemini surfactants and tungsten trioxide, and solvent extraction strategy contributed together to the coexistence of WO3 mesostructures and crystalline pore walls.

Synthesis and self-assembly of new light-sensitive Gemini surfactants containing an azobenzene group

A homologue of dissymmetric quaternary ammonium Gemini surfactants, hexanediyl-α-(butylazobenzene dimethylammonium)-ω-(alkyldimethylammonium) dibromides (referred to as a4-6- m, m = 12, 14, 16), and a symmetric quaternary ammonium Gemini surfactant, hexanediyl-α,ω-bis(butylazobenzene dimethylammonium bromide) (referred to as a4-6-4a), have been synthesized. The Krafft temperature at 1 wt% concentration was determined to be 17–32 °C for dissymmetric a4-6- m homologues depending on the length of aliphatic tail and 42.5 °C for symmetric a4-6-4a. After UV light irradiation, the content of their cis-azobenzene isomers reaching photostationary state was estimated to be ca. 67–71% for the dilution. The critical micelle concentration ( cmc) of a4-6- m is close to that of 12-6- m, indicating that the both are equivalent from the self-assembly point of view. But the cmc of a4-6-4a is higher than that of a4-6-12 or 12-6-12, showing the effect of the steric inhibition on aggregation owing to the two rigid terminal azobenzene groups per molecule. After UV light irradiation, the twisted cis-azobenzene groups in both a4-6- m and a4-6-4a molecules shows more obvious steric inhibition, resulting in a larger cmc than that of the trans-surfactants.

NMR Study of the Dynamics of Cationic Gemini Surfactant 14−2−14 in Mixed Solutions with Conventional Surfactants

Three kinds of conventional surfactants, namely, two nonionic surfactants [polyethylene glycol (23) lauryl ether (Brij-35) and Triton X-100 (TX-100)], one cationic surfactant [n-tetradecyltrimethyl ammonium bromide (TTAB)], and an anionic surfactant [sodium n-dodecyl sulfate (SDS)}, were mixed into the quaternary ammonium gemini surfactant [C(14)H(29)N(+)(CH(3))(2)](2)(CH(2))(2).2Br(-) (14-2-14) in aqueous solution. The exchange rate constants between 14-2-14 molecules in the mixed micelles and those in the bulk solution were detected using two nuclear magnetic resonance (NMR) methods: one-dimensional (1D) line shape analysis and two-dimensional (2D) exchange spectroscopy (EXSY). The results obtained from these two methods were consistent. Both showed that mixing a nonionic conventional surfactant, either Brij-35 or TX-100, enhanced the exchange process between the 14-2-14 molecules in the mixed micelles and those in the bulk solution. In contrast, the anionic surfactant SDS and the cationic surfactant TTAB slowed the process slightly.

Strong effect of NaBr on self-assembly of quaternary ammonium gemini surfactants at air/water interface and in aqueous solution studied by surface tension and fluorescence techniques

The effects of NaBr on the adsorption of alkanediyl-bis-(dimethyl dodecyl- ammonium bromide) (referred to as C12-s-C12 2Br) at the air/water interface and on the micellization in the solution have been investigated by surface tension and fluorescence techniques. The results showed that the addition of NaBr greatly enhances their efficiency and effectiveness in surface tension reduction as well as the ability of micellization, even induces strong premicellar aggregation before the cmc. These were attributed to the unique molecular structure of gemini surfactant, where the flexible polymethylene chain was the spacer linking the two quaternary ammonium heads. By a short spacer, the charges of the two quaternary ammonium head groups are concentrated. Even for a long spacer (s = 12), since it is bent toward the alkyl tails, the similar effect is also produced. This results in the high sensitivity of their ionic head groups to salt. Besides, the addition of salt also effectively promotes the hydrophobic interaction between the alkyl tails of gemini surfactants.

Adsorption of Photosensitive Quaternary Ammonium Gemini Surfactant a4-6-<em>m</em> at the Air/Water Interface

合成了3种不对称结构的季铵盐Gemini表面活性剂a4-6-m,分子的一根疏水链是偶氮苯为端基的4个亚甲基链,另一根是不同长度的脂肪链（m=12,14,16）.研究结果表明,反式偶氮苯封端的a4-6-m在气/液界面上以直立方式排列,偶氮苯端基间的π-π相互作用导致吸附分子较为紧密地排列,但吸附层外表面含有偶氮苯成分使临界胶束浓度（cmc）时的表面张力（γcmc）较大.紫外光激发使反式结构偶氮苯变为顺式结构,这些极性较强的顺式偶氮苯夹杂在直立的烷烃链间,增强的偶极-偶极相互作用促进了分子紧密排列,使分子占据面积（Amin）略微减小.增长脂肪链长度有助于降低临界胶团浓度和C20（使水的表面张力降低20mN·m^-1时所需的表面活性剂浓度）,但对γcmc影响不大.

Biodegradable gemini surfactants. Correlation of area per surfactant molecule with surfactant structure

Values of the area per surfactant molecule of various single chain and gemini quaternary ammonium surfactants containing biodegradable amide and ester groups are obtained from the surface tension measurements and they are mutually compared. It was found that surfactant molecules with the ester group in their structure occupy smaller area at the air/water interface than the corresponding molecules with the amide group, mainly due to the higher conformational flexibility of ester groups. In decreasing the area per surfactant molecule value, hydrogen bonding (both inter- and intramolecular) plays a significant role when amide groups are present in the spacer of a gemini molecule. They must be separated by a polymethylene chain or a flexible group such as cyclohexane which is short enough to allow intramolecular hydrogen bonds. The flexible cyclohexane group with the amide group in single chain surfactants may lead to the formation of intermolecular hydrogen bonds among surfactant molecules which also results in the reduction of the area per surfactant molecule.

1H NMR Study on Pre-micellization of Quaternary Ammonium Gemini Surfactants

Two quaternary ammonium Gemini surfactant series, 12-s-12, ([C(12)H(25)N+ (CH(3))(2)](2)(CH(2))(s).(2)Br(-)) and 14-s-14 ([C(14)H(29)N(+)(CH(3))(2)](2)(CH(2))(s).(2)Br(-)), where s = 2, 3, and 4, have been studied by the use of (1)H NMR in aqueous solution at concentrations below their critical micelle concentrations (CMC) at 25 degrees C. The appearance of a second set of peaks for the 14-s-14 series and the changes in chemical shifts, line widths, and line shapes of the 12-s-12 series with increasing concentration below the CMC are interpreted as evidence for the formation of premicelle aggregates (oligomers) that appear at approximately one-half their CMC values. Self-diffusion coefficients (D) and transverse relaxation times (T(2)) have also been detected and support the results obtained by (1)H NMR.