Physicochemical properties of quaternary ammonium bromide-type trimeric surfactants

Trimeric surfactants of quaternary ammonium bromide (m-2-m-2-m, where m is the hydrocarbon chain length of 8, 10, or 12) with three hydrocarbon chains and three hydrophilic groups connected by two ethylene spacer chains were synthesized by the reaction of N,N,N',N",N"-pentamethyldiethylenetriamine and the corresponding alkyl bromide. Their physicochemical properties were characterized by surface tension, static and dynamic light-scattering, and fluorescence spectrum of pyrene techniques. The critical micelle concentrations (cmc's) of m-2-m-2-m shifted to lower concentrations with increasing hydrocarbon chain length, and their values were smaller by about one to three orders of magnitude than those of the corresponding dimeric (m-2-m) and monomeric surfactants (C(m)TAB) with the same hydrocarbon chain length. Of these surfactants, 10-2-10-2-10 showed the greatest efficiency in lowering the surface tension and provided the smallest occupied area per molecule, indicating that it adsorbs more compactly at the air/water interface. In addition, from the static and dynamic light-scattering measurements, the aggregation numbers of the trimeric surfactants at the cmc were very small, and two hydrodynamic diameters above the cmc were observed.     

Zwitterionic heterogemini surfactants containing ammonium and carboxylate headgroups. 1. Adsorption and micellization

Zwitterionic heterogemini surfactants with two hydrocarbon chains and two different hydrophilic groups, N,N-dimethyl-N-[2-(N'-alkyl-N'-beta-carboxypropanoylamino)ethyl]-1-alkylammonium bromides (2C(n)AmCa, where n represents the hydrocarbon chain lengths of 8, 10, 12, and 14), were synthesized by N,N-dimethylethylenediamine with alkyl bromide, followed by reaction with succinic anhydride. One of the hydrophilic groups is a carboxylate anion, and the other is an ammonium cation. Their physicochemical properties were characterized by measuring equilibrium and dynamic surface tension, fluorescence intensity of pyrene, and light-scattering intensity. A relationship between a logarithm of critical micelle concentration (cmc) and hydrocarbon chain length showed a linear decrease upon increasing chain length and then a departure from linearity at n = 14. This is due to the existence of premicellar aggregations at concentrations below the cmc for n = 14. The surface tension of 2C(n)AmCa reached 27-30 mN m(-1) at each cmc, indicating efficiencies typical of hydrocarbon chain surfactants. The adsorbing rate at the air/water interface became slow with an increase of the chain length. From the fluorescence intensity ratios of 373 and 384 nm using pyrene as a probe, for n = 8, 10, and 14, the pyrene was solubilized in surfactant micelles at around the cmc, whereas for n = 12 the pyrene was solubilized from a concentration of 10-fold the cmc. The scattering intensities by dynamic light scattering also increased from around these concentrations for each chain length, showing the formation of aggregates in solution.     

Mixed micellar properties of cationic trimeric-type quaternary ammonium salts and anionic sodium n-octyl sulfate surfactants

The properties of quaternary ammonium salt-type cationic trimeric surfactants (m-2-m-2-m, m represents the carbon atom number in alkyl chain lengths of 8, 10, and 12) and oppositely charged anionic monomeric surfactant, sodium n-octyl sulfate (SOS), were characterized by employing several techniques such as static surface tension, fluorescence spectroscopy, and dynamic light-scattering measurements. The critical micelle concentrations (cmc) of m-2-m-2-m were much lower than those of the corresponding dimeric and monomeric surfactants, and decreased with increasing chain length. The addition of SOS to m-2-m-2-m solutions resulted in a further decrease of the cmc. The mixed surfactants showed higher efficiencies in lowering the surface tension than the individual surfactants. The fluorescence measurements suggested the formation of mixed micelles with a hydrophobic environment in the solutions even at lower concentrations. The dynamic light-scattering study indicated the presence of two different kinds of aggregates with different hydrodynamic diameters. The larger one was attributed to the mixed micelle of m-2-m-2-m and SOS. These results indicated a decline of the electrostatic repulsion between cationic head groups through the incorporation of anionic surfactant into the mixed surfactants.     

Adsorption and micellization behavior of novel gluconamide-type gemini surfactants

The adsorption and micellization behavior of novel sugar-based gemini surfactants (N,N(')-dialkyl-N,N(')-digluconamide ethylenediamine, Glu(n)-2-Glu(n), where n is the hydrocarbon chain length of 8, 10 and 12) has been studied on the basis of static/dynamic surface tension, fluorescence, dynamic light scattering (DLS) and cryogenic transmission electron microscope (cryo-TEM) data. The static surface tension of the aqueous Glu(n)-2-Glu(n) solutions measured at the critical micelle concentration (cmc) is observed to be significantly lower than that of the corresponding monomeric surfactants. This suggests that the gemini surfactants, newly synthesized in the current study, are able to form a closely packed monolayer film at the air/aqueous solution interface. The greater ability in the molecular association is supported by the remarkably (approximately 100-200 times) lower cmc of the gemini surfactants compared with the corresponding monomeric ones. With a combination of the fluorescence and DLS data, a structural transformation of the Glu(n)-2-Glu(n) micelles is suggested to occur with an increase in the concentration. The cryo-TEM measurements clearly confirm the formation of worm-like micelles of Glu(12)-2-Glu(12) at the concentration well above the cmc.     

Synthesis and Surface Properties of N-Alkyl-N-methylgluconamides and N-Alkyl-N-methyllactobionamides

Three series of nonionic N-alkylaldonamides, N-alkyl-N-methylgluconamides (Cn-MGA, Cn: n-C(10)H(21), n-C(12)H(25), n-C(14)H(29), n-C(16)H(33), and n-C(18)H(37)), N-alkyl-N-methyllactobionamides (Cn-MLA, alkyl as above-mentioned), and N-oleyl-N-methylglucon/lactobionamide, were synthesized in the reaction of an appropriate N-alkyl-N-methylamine with delta-D-glucolactone and lactobionic acid, respectively. Krafft temperatures of aqueous solutions and surface properties of these surfactants at 20 degrees C, i.e., surface excess concentration, Gamma(cmc), surface area demand per molecule, A(min), efficiency in surface tension reduction, pC(20), effectiveness in surface tension reduction, Pi(cmc), critical micelle concentration, CMC, and CMC/C(20) parameter as well as standard free energies of adsorption, DeltaG degrees (ads), and of micellization, DeltaG degrees (mic), were determined. It was shown that introduction of the methyl group to the amide nitrogen increased the solubility of the surfactants, which was confirmed by their Krafft temperatures. Lactobionamides are more water soluble than gluconamides. On the other hand, the Cn-MGA surfactants are more surface active than the respective Cn-MLA ones. This observation is based on the determined adsorption and micellization parameters. The presence of one double bond in a hydrocarbon chain as in oleyl-amides increases their hydrophilic character compared with that of saturated C18 derivatives. No distinct differences were observed between the A(min) values obtained for both series studied, although they differ markedly in the size of the hydrophilic groups. Copyright 2001 Academic Press.     

Surface-active, micellar, and antielectrostatic properties of bis-ammonium salts

A series of new cationic surfactants, bis-quaternary ammonium dibromides, were synthesized. The properties of these surfactants were characterized by surface tension measurements, conductivity study, and dynamic light scattering. The surface properties, such as surface excess concentration, Gamma(cmc), surface area demand per molecule, A(min), efficiency in surface tension reduction, pC(20), the effectiveness of surface tension reduction, gamma(min), critical micelle concentration, cmc, and standard free energy of micellization, DeltaG(mic)(0) and DeltaG(ads)(0), were obtained by means of surface tension measurements. The antielectrostatic properties were investigated by measuring the surface resistance, the half-charge decay time, and the maximum voltage induced on polyethylene films and propylene unwoven fabrics. Critical micellar concentrations (cmc) of investigated salts were much lower than those of the monomeric salt DTAC. The results obtained in this work were compared to analogous bis-quaternary ammonium dichlorides and well-known gemini cationic surfactants. It was found that the type of counterion had an impact on the values of the micelle ionization degree and the hydrodynamic diameters. Larger aggregates were found for bis-quaternary ammonium dibromides, which had smaller values of the ionization micelle degree than bis-quaternary ammonium dichlorides. Moreover, the antielectrostatic effect strongly depended on the kind of counterion. All investigated salts had very good antistatic properties.     

Sugar-based gemini surfactants with peptide bonds-synthesis, adsorption, micellization, and biodegradability

The sugar-based gemini surfactant with peptide bonds, N,N'-bisalkyl-N,N'-bis[2-(lactobionylamide)ethyl]hexanediamide (2C(n)peLac, in which n represents hydrocarbon chain lengths of 12 and 16), was synthesized by reacting adipoyl chloride with the corresponding monomeric surfactant N-alkyl-N'-lactobionylethylenediamine (C(n)peLac), which was obtained by reacting ethylenediamine with alkyl bromide and lactobionic acid. The adsorption and micellization properties of C(n)peLac and 2C(n)peLac were characterized by the measurement of their equilibrium and dynamic surface tension, steady-state fluorescence using pyrene as a probe, dynamic light scattering (DLS), and time-resolved fluorescence quenching (TRFQ), and their biodegradability was also investigated. The critical micelle concentration (cmc) decreases with an increase in the hydrocarbon chains from monomeric to gemini surfactants, whereas it increases with an increase in the chain length from 12 to 16 for both systems. The increases in both the hydrocarbon chain and the chain length of sugar-based surfactants reduce surface activities such as the ability to lower the surface tension, the occupied area per molecule, and the adsorption rate at the air/water interface. The sugar-based surfactants C(n)peLac and 2C(n)peLac exhibit unique aggregation behavior in aqueous solution. The DLS results indicate that the apparent hydrodynamic diameter of C(n)peLac micelles decreases sharply with increasing concentration, whereas that of 2C(n)peLac micelles decreases gradually. From the TRFQ measurement, it was observed that, as concentration increases, the aggregation numbers are almost constant for C(n)peLac, whereas they increase for 2C(n)peLac. These results imply that loosely packed micelles formed by sugar-based surfactants become tightly packed micelles as the concentration increases. Furthermore, it was found that 2C(n)peLac shows lower biodegradability than does C(n)peLac because it contains tertiary amines in the molecule.     

Enhanced interfacial properties of novel amino acid-derived surfactants: Effects of headgroup chemistry and of alkyl chain length and unsaturation

Amino acid-derived surfactants have increasingly become a viable biofriendly alternative to petrochemically based amphiphiles as speciality surfactants. Herein, the Krafft temperatures and critical micelle concentrations (cmc) of three series of novel amino acid-derived surfactants have been determined by differential scanning microcalorimetry and surface tension measurements, respectively. The compounds comprise cationic molecules based on serine and tyrosine headgroups and anionic ones based on 4-hydroxyproline headgroups, with varying chain lengths. A linear dependence of the logarithm of cmc on chain length is found for all series, and in comparison to conventional ionic surfactants of equal chain length, the new amphiphiles present lower cmc and lower surface tension at the cmc. These observations highlight their enhanced interfacial performance. For the 18-carbon serine-derived surfactant the effects of counterion change and of the presence of a cis-double bond in the alkyl chain have also been investigated. The overall results are discussed in terms of headgroup and alkyl chain effects on micellization, in the light of available data for conventional surfactants and other types of amino acid-based amphiphiles reported in the literature.     

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

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

N-酰基-L-丝氨酸钠表面活性剂的合成和胶束化热力学性质

以L-丝氨酸和长链酰氯为原料,合成了3种不同碳链长度（n=8,12,14）的N-酰基-L-丝氨酸。 并以1H NMR、ESI-MS和元素分析对3种目标产物进行了表征。 采用表面张力法研究了N-酰基-L-丝氨酸钠在298、308、318和328 K时水溶液中的聚集行为,确定了临界胶束浓度（cmc）、临界胶束浓度下的最低表面张力（γcmc）、表面饱和吸附量Γmax。 由cmc和温度的关系,应用相分离模型计算了胶束化热力学参数ΔGom、ΔHom和ΔSom。 结果表明,ΔGom＜0,ΔHom的绝对值比-TΔSom绝对值小的多,说明胶束化过程为熵驱动过程,随着温度的升高,胶束化过程是熵-焓补偿的过程。     

Equilibrium and dynamic surface tension properties of partially fluorinated quaternary ammonium salt gemini surfactants

The equilibrium and dynamic surface tension properties of a partially fluorinated quaternary ammonium salt gemini surfactant 1,2-bis[dimethyl-(3-perfluoroalkyl-2-hydroxypropyl)ammonium]ethane bromide (C(n)(F)C3-2-C3C(n)F, where n represents fluorocarbon chain lengths of 4, 6, and 8) were investigated, and the effects of the fluorocarbon chain length and the number of chains on them were discussed. The plot of the logarithm of the critical micelle concentration (cmc) against the fluorocarbon chain length for C(n)(F)C3-2-C3C(n)F showed a linear decrease with an increase in chain length. On the basis of the slope of this plot, it was found that the variation in cmc with respect to the chain length is large for fluorinated gemini surfactants. The surface tension at the cmc decreased significantly; this surface tension value is lower than that of conventional fluorinated monomeric surfactants. In particular, the lowest value was 13.7 mN m(-1) for n = 8. Furthermore, it was confirmed that the kinetics of adsorption at the interface decrease with an increase in the fluorocarbon chain length and the concentration.     

Thermodynamics of micellization of multiheaded single-chain cationic surfactants

The energetics of micelle formation of three single-chain cationic surfactants bearing single (h = 1), double (h = 2), and triple (h = 3) trimethylammonium [(+)N(CH(3))(3)] headgroups have been investigated by microcalorimetry. The results were compared with the microcalorimetric data obtained from well-known cationic surfactant, cetyl trimethylammonium bromide (CTAB), bearing a single chain and single headgroup. The critical micellar concentrations (cmc's) and the degrees of counterion dissociation (alpha) of micelles of these surfactants were also determined by conductometry. The cmc and the alpha values increased with the increase in the number of headgroups of the surfactant. The relationship between the cmc of the surfactant in solution and its free energy of micellization (DeltaG(m)) was derived for each surfactant. Exothermic enthalpies of micellization (DeltaH(m)) and positive entropies of micellization (DeltaS(m)) were observed for all the surfactants. Negative DeltaH(m) values increased from CTAB to h = 1 to h = 2 and decreased for h = 3 whereas DeltaS(m) values decreased with increase in the number of headgroups. The DeltaG(m) values progressively became less negative with the increase in the number of headgroups. This implies that micelle formation becomes progressively less favorable as more headgroups are incorporated in the surfactant. From the steady-state fluorescence measurements using pyrene as a probe, the micropolarities sensed by the probe inside various micelles were determined. These studies suggest that the micelles are more hydrated with multiheaded surfactants and the micropolarity of micelles increases with the increase in the number of headgroups.     

表面活性素分子结构对其胶束化行为的影响

采用表面张力、界面张力、荧光、动态光散射(DLS)和冷冻刻蚀电镜(FF-TEM)等方法, 研究了由Bacillus subtilis HSO121所产生的一组表面活性素的胶束化行为. 通过对表面活性素溶液表面张力、表面活性素对水/正己烷界面张力的影响、表面活性素胶束微极性以及胶束粒径和形态的研究, 发现随着表面活性素脂肪链长度的增加, 其表界面活性增强, 溶液中趋向于形成更大的聚集体.     

Gemini表面活性剂烷烃尾链在吸附和聚集过程中的疏水协同效应(英文)

以表面张力法测定了系列Gemini表面活性剂m-6-m以及对应单体表面活性剂CmTABr的临界胶束浓度(cmc)和降低水表面张力20mN·m-1需要的浓度(pC20).比较这些参数表明m-6-m胶束化和在界面吸附的能力均强于CmTABr,这被归结为Gemini表面活性剂烷烃尾链间的疏水协同效应.与不对称Gemini表面活性剂12-6-m比较,对称的Gemini结构更有利于表面活性剂的聚集和吸附.     

Synthesis,micellization properties,and cytotoxicity trends of N-hydroxyethyl-3-alkyloxypyridinium surfactants

N-hydroxyethyl-3-alkyloxypyridinium amphiphiles have been synthesized and characterized by various spectroscopic techniques. Self-assembling properties of these amphiphiles have been studied by surface tension, conductivity, and fluorescence measurements. Basic micellization parameters like critical micelle concentration (cmc), surface tension at the cmc (γ _cmc), adsorption efficiency (pC₂₀), effectiveness of surface tension reduction (Π _cmc), maximum surface excess concentration (Γ _max) and minimum surface area/molecule (A _min), and Gibbs free energy of the micellization (ΔG⁰ _mic) have also been determined. The micellization of these 3-alkyloxypyridinium halides in aqueous phase have been found to be exothermic and entropy-driven as assessed by conductivity measurements at different temperatures. Thermal degradation of these surfactants has also been assessed by thermal gravimetric analysis under nitrogen atmosphere. Further, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay of these surfactants on C6 glioma cells show them to be less toxic than conventional cationic surfactants.     

新型Gemini咪唑表面活性剂的合成及表面性能

以2,2-双(溴甲基)-1,3-丙二醇为连接基合成了新型的连接基为枝状的Gemini咪唑表面活性剂2,4-二(溴化-3-烷基咪唑)-1,3-丙二醇([Cn-P-Cnim]Br2,n=10,12,14).产物经核磁共振氢谱(1H NMR)、红外(IR)光谱和元素分析等进行了分析,证明所得产物即为目标产物.通过表面张力法和电导法测量其表面活性并计算胶束形成热力学参数(ΔG m—0,ΔH m—0,ΔS m—0).结果表明,25℃时3种表面活性剂均具有很高的表面活性,胶束的形成是自发的熵驱动过程.     

Synthesis and properties of ionic liquid-type Gemini imidazolium surfactants

A series of ionic liquid-type Gemini imidazolium surfactants with four-methylene spacer groups were synthesized ([C(n)-4-C(n)im]Br(2), n=10, 12, 14). The surface activity and thermodynamic properties of micellization between the Gemini imidazolium surfactants and their corresponding monomers ([C(n)mim]Br, n=10, 12, 14) were compared by means of surface tension and electrical conductivity measurements. The values of cmc, gamma(cmc), pc(20), Gamma(max), and A(min) derived from surface tension measurement at 25 degrees C suggest that the surface activity of [C(n)-4-C(n)im]Br(2) is higher than that of [C(n)mim]Br. While the thermodynamic parameters of micellization (DeltaG(m)(o), DeltaH(m)(o), DeltaS(m)(o)) derived from electrical conductivity indicate that the micellization of [C(n)-4-C(n)im]Br(2) is entropy-driven, aggregation of [C(n)mim]Br is entropy-driven at low temperature but enthalpy-driven at high temperature. Finally, the activation energy of conductance (E(a)) that is associated with the effective charge is also obtained for [C(n)-4-C(n)im]Br(2) and it is constant below the cmc, but it increases above the cmc.     

反离子对氟表面活性剂的影响1. 表面活性及胶团化作用

通过表面张力和荧光探针法研究了全氟辛酸钠、全氟辛酸铵以及全氟辛酸四烷基铵[C₇F₁₅COON(C_nH_2n+1)₄, n＝1, 2, 3, 4]的表面活性以及胶团化作用, 系统地讨论了各种反离子, 特别是反离子大小的影响. 结果表明, 与普通碳氢表面活性剂不同, 反离子对这类氟表面活性剂的表面活性以及胶团化作用有很大影响. 表面活性剂的临界胶束浓度(cmc)随反离子的增大而下降; 饱和吸附层中平均每个分子所占的面积则大致随反离子的增大而增大. 而表面张力的变化则较为复杂. cmc时的表面张力随反离子的增大先上升(从全氟辛酸铵到全氟辛酸四乙铵)后下降(从全氟辛酸四乙铵到全氟辛酸四丁铵). 通过反离子的空间位阻、疏水性、插入以及电荷屏蔽效应对上述结果做了解释.     

Mixed micelles containing sodium oleate: the effect of the chain length and the polar head group

We have investigated the mixing behavior of binary mixtures of the alkylglucosides (CnG) octyl beta-D-glucoside and decyl D-glucoside in combination with sodium oleate (NaOl), and the amine oxide surfactants (AO) N,N-dimethyldodecylamine oxide, N,N-bis (2-hydroxyethyl)dodecylamine oxide, and 3-lauramidopropyl-N,N-dimethylamine oxide in combination with NaOl. From the equilibrium surface tension measurements, the critical micelle concentration (cmc) data were obtained as functions of the composition. Values of the cmc were analyzed according to both the regular solution model developed by Rubingh for mixed micelles and Maeda's formulation for ionic/nonionic mixed micelles. Two interaction parameters, beta and B1, were estimated from the regular solution model and Maeda's formulation, respectively. For NaOl/CnG mixed systems, a decrease in the hydrocarbon chain length of CnG resulted in a stronger interaction with NaOl from both beta and B1 values. For NaOl/AO mixed systems, the bulkiness of a polar head group of AO surfactants influenced the interaction between NaOl and AO. The dynamic surface tension measurements show that all surface tension values of surfactant solutions examined decreased with the time. We found that the time dependence of surface tension values for NaOl mixed systems was greatly influenced by the presence of NaOl rather than the other component.     

Thermodynamics of micellization of benzyl(2-acylaminoethyl)dimethylammonium chloride surfactants in aqueous solutions: a conductivity and titration calorimetry study

The enthalpies of micellization of the surfactant series benzyl(2-acylaminoethyl)dimethylammonium chlorides, RABzMe(2)Cl, have been determined by calorimetry and conductivity measurements in the temperature range 15-75 degrees C. Here R stands for an acyl group containing 10-16 carbon atoms and A, Bz, and Me stand for NH(CH(2))(2)N(+), benzyl, and methyl groups, respectively. The enthalpy of micellization, DeltaH(mic) degrees , and the critical micelle concentration, cmc, were calculated directly from calorimetric data. The free energy of micellization, DeltaG(mic) degrees , was obtained from the cmc and the conductance-based degree of counterion dissociation. There is an excellent agreement between DeltaG(mic) degrees calculated from the data of both techniques, but the DeltaH(mic) degrees , the entropy of micellization, values differ. The dependence of the thermodynamic parameters of micellization on the chain length of the hydrophobic group and on the temperature has been analyzed by considering the delicate balance between the factors that contribute to micelle formation, including transfer of the surfactant hydrocarbon chain from the aqueous environment to the micelle, with concomitant release of the solvating water molecules, and the effect of temperature on the structure of water. DeltaG(mic) degrees is more negative, that is, more favorable for RABzMe(2)Cl than for the structurally related alkylbenzyldimethylammonium chlorides. This is attributed to direct and water-mediated H bonding between the amide groups of molecules of the former series.