Conductometric study of antidepressant drug-cationic surfactant mixed micelles in aqueous solution

Conductivity measurements have been carried out on aqueous solutions of two antidepressant drugs (nortriptyline hydrochloride and clomipramine hydrochloride) with four cationic surfactants (monomeric: cetyltrimethylammonium bromide, tetradecylammonium bromide; dimeric: 1,5-pentanediyl-alpha-omega-bis(hexadecyldimethylammonium bromide), 1,4-butanediyl-alpha,omega-bis(hexadecyldimethylammonium bromide) as well as with sodium chloride. Counterions from NaCl adsorb to the charged headgroup of the drug molecules and reduce the repulsion, hence cmc decreases. cmc values decreased with the addition of surfactants indicating mixed micelle formation. Experimental mole fraction of surfactants in micelle (X1) and their ideal values (X1 id) also support this explanation. Interaction parameter, beta, and excess free energy of micellization are negative suggesting synergism in mixed state. Activity coefficients are less than unity which means non-ideal mixing.     

Alkanediyl-alpha,omega-bis(dimethylalkylammonium bromide) surfactants 10. Behavior in aqueous solution at concentrations below the critical micellization concentration: an electrical conductivity study

Ion pairing and premicellar association have been often invoked to explain results obtained in studies of aqueous solutions of ionic dimeric surfactants (gemini surfactants), mainly by means of surface tension and electrical conductivity, at concentrations below the critical micellization concentration (cmc). The present work was undertaken in an attempt to find out under which conditions these effects come into play. For this purpose the electrical conductivity of solutions of many dimeric surfactants of the type spacer-alpha,omega-bis(alkyldimethylammonium bromide) have been measured. The alkyl chain contained m=10-18 carbon atoms. The spacer group was either an alkanediyl with s carbon atoms (m-s-m surfactants) or a xylylene m-xylyl-m surfactants). The results show that ion pairing occurs in solutions of m-s-m dimers with m< or =10, mostly as a result of their high cmc values. The results for 12-s-12 dimers with s< or =10 and for 12-xylyl-12 showed no evidence of either ion pairing or premicellar association. Premicellar association was present for 12-s-12 dimers with s> or =12, for m-8-m dimers with m> or =14, and for 16-xylyl-16. It showed through a positive curvature of the specific conductivity versus concentration plot and the presence of a maximum in the equivalent conductivity vs (concentration)(0.5) plot at concentrations below the cmc. The free energy associated with the premicellar association of m-8-m dimers has been estimated from the available cmc and micelle ionization degree data.     

混合胶束中Gemini阳离子表面活性剂14-s-14与常规表面活性剂的协同作用:连接臂及反离子效应(英文)

The mixed micelle formation of binary cationic 14-s-14 gemini with conventional single chain surfactants was studied by conductivity measurements.The critical micelle concentration(cmc) and the degree of counterion binding values(g) of the binary systems were determined.The results were analyzed by applying regular solution theory(RST) to calculate micellar compositions(X),activity coefficients(f1,f2),and the interaction parameters(β).The synergistic interactions of all the investigated cationic gemini+conventional surfactant combinations were found to be dependent upon the length of hydrophobic spacer of the gemini surfactant.The excess Gibbs free energy of mixing was evaluated,and it indicated relatively more stable mixed micelles for the binary combinations.     

乙醇/水混合溶剂中Gemini表面活性剂的表面性质

通过对Gemini表面活性剂12-s-12 (Et)(s=4, 6, 8, 10, 12)体系在乙醇/水混合溶剂中的表面张力曲线的测定, 对该体系的表面性质进行了研究. 发现随乙醇/水比例变化, Gemini各种表面化学性质, 如临界胶束浓度(cmc)、表面张力(γcmc)、饱和吸附量(Γmax)和最小分子占有面积(Amin)等的变化规律. 拓展了Gemini表面活性剂在混合溶剂中表面吸附的研究.     

Studies of mixed micelle formation between cationic gemini and cationic conventional surfactants

Mixed micellization of dimeric cationic surfactants tetramethylene-1,4-bis(hexadecyldimethylammonium bromide)(16-4-16), hexamethylene-1,6-bis(hexadecyldimethylammonium bromide) (16-6-16) with monomeric cationic surfactants hexadecyltrimethylammonium bromide (CTAB), cetylpyridinium bromide (CPB), cetylpyridinium chloride (CPC), and tetradecyltrimethylammonium bromide (TTAB) have been studied by conductivity and steady-state fluorescence quenching techniques. The behavior of mixed systems, their compositions, and activities of the components have been analyzed in the light of Rubingh's regular solution theory. The results indicate synergism in the binary mixtures. Ideal and experimental critical micelle concentrations (i.e., cmc(*) and cmc) show nonideality, which is confirmed by beta values and activity coefficients. The micelle aggregation numbers (N(agg)), evaluated using steady-state fluorescence quenching at a total concentration of 2 mM for CTAB/16-4-16 or 16-6-16 and 5 mM for TTAB/16-4-16 or 16-6-16 systems, indicate that the contribution of conventional surfactants was always more than that of the geminis. The micropolarity, dielectric constant and binding constants (K(sv)) of mixed systems have also been evaluated from the ratios of respective peak intensities (I(1)/I(3) or I(0)/I(1)).     

Self-aggregation of binary mixtures of alkyltriphenylphosphonium bromides: a critical assessment in favor of more than one kind of micelle formation

The micellization behavior of binary combinations of alkyltriphenylphosphonium bromides (ATPBs) with alkyl chain carbons 10, 12, 14, and 16 has been studied by conductometry and calorimetry. The combinations C(10)-C(12), C(10)-C(14), C(10)-C(16), C(12)-C(14), C(12)-C(16), and C(14)-C(16) were found to form two cmc's by both the methods, with good agreement, except C(14)-C(16)TPB, which has evidenced only a single cmc by calorimetry for all combinations. The combinations C(10)-C(12) (for both cmc(1) and cmc(2)) and C(10)-C(14)TPB (for cmc(2)) formed ideal mixtures, whereas the rest were nonideal. In the nonideal binary mixtures, the ATPB components showed antagonistic interaction with each other. The cmc, interaction parameter (beta), mixed micellar composition, extent of counterion binding, and thermodynamic parameters for the micellization process have been reported and discussed. The enthalpy of mixed micelle formation has been found to have a fair correlation with a Clint-type relation applicable to ideal binary mixtures of surfactants.     

Alkanediyl-alpha,omega-bis(dimethylalkylammonium bromide) surfactants 9. Effect of the spacer carbon number and temperature on the enthalpy of micellization

The enthalpies of dilution of micellar solutions of several 12-s-12 dimeric surfactants of the alkanediyl-alpha,omega-bis(dodecyldi-methylammonium bromide) type, differing by the carbon number s of the alkanediyl spacer, and of dodecyltrimethylammonium bromide (DTAB) have been measured calorimetrically, in a range of concentrations extending from well below to well above the critical micelle concentration (cmc). The results permitted the determination of the enthalpy of micellization, DeltaH degrees (M), of the investigated surfactants at 25 and 35 degrees C. The values of DeltaH degrees (M) were always negative and became more negative as the temperature was increased. The plot of -DeltaH degrees (M) against s showed a shallow minimum at about s=5 and a large decrease of -DeltaH degrees (M) going from 12-2-12 to 12- 4-12. This effect has been attributed to the contribution to DeltaH degrees (M) of the hindered rotation of the dodecyl chains around the spacer C-C bond for 12-2-12. This hindrance is shown to rapidly disappear when s is increased from 2 to above 4. The specific heats of micellization, the free energies of micellization, and the entropies of micellization (DeltaS degrees (M)) have been calculated using the DeltaH degrees (M) values and the reported cmc and micelle ionization degree data for 12-s-12 surfactants and DTAB. For all surfactants the results show that TDeltaS degrees (M)>-DeltaH degrees (M), indicating an entropy-driven micellization.     

Synthesis and solution properties of gemini surfactants containing oleyl chains

Gemini surfactants 18:1-s-18:1, where s = 2, 3, and 6 methylene groups and 18:1 refers to oleyl carbon chains, have been synthesized, characterized and a number of micelle solution properties measured by using electrical conductance, fluorescence probe emission, light scattering (DLS), surface tension and isothermal titration calorimetry (ITC) methods at 25 degrees C. The cmc values of 18:1-2-18:1, 18:1-3-18:1, and 18:1-6-18:1 were found to be 26.9, 23.4, and 18.0 microM, respectively, using the electrical conductance method. Surface tension results suggest that in 0.01 N NaCl solutions, the s = 2 and 3 members of the series form multilayer rather than monolayer structures, while the s = 6 homologue adopts a close-packed arrangement. This is consistent with DLS and EM measurements which show vesicle formation for the s = 2 and 3 compounds, and micelle formation for the s = 6 compound. The enthalpies of micellization (deltaH degrees (M)) are more exothermic for the 18:1-s-18:1 series of surfactants, than for the 12-s-12 series. The differences are rationalized in terms of steric and configurational contributions to deltaH degrees (M) arising from difficulties associated with packing of the bulky cis-9-octadecene tails.     

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.     

Thermodynamic and structural characterization of zwitterionic micelles of the membrane protein solubilizing amidosulfobetaine surfactants ASB-14 and ASB-16

Surface tension and isothermal titration calorimetry (ITC) were used to determine the critical micelle concentration (cmc) of the zwitterionic amidosulfobetaine surfactants ASB-14 and ASB-16 (linear-alkylamidopropyldimethylammoniopropanosulfonates) at 25 °C. The cmc and the heat of micellization were determined from 15 to 75 °C by ITC for both surfactants. The increase in temperature caused significant changes in the enthalpy and in the entropy of micellization, with small changes in the standard Gibbs energy (ΔG(mic)), which is consistent to an enthalpy?entropy compensation with a compensatory temperature of 311 K (ASB-14) and 314 K (ASB-16). In the studied temperature range, the heat capacity of micellization (ΔC(p)(mic)) was essentially constant. The experimental ΔC(p)(mic) was lower than that expected if only hydrophobic interactions were considered, suggesting that polar interactions at the head groups are of significant importance in the thermodynamics of micelle formation by these surfactants. Indeed, a NMR NOESY spectrum showed NOEs that are improbable to occur within the same monomer, resulting from interactions at the polar head groups involving more than one monomer. The ITC and NMR results indicate a tilt in the polar headgroup favoring the polar interactions. We have also observed COSY correlations typical of dipolar interactions that could be recovered with the partial alignment of the molecule in solution, which results in an anisotropic tumbling. The anisotropy suggested an ellipsoidal shape of the micelles, which results in a positive magnetic susceptibility, and ultimately in orientation induced by the magnetic field. Such an ellipsoidal shape was confirmed from results obtained by SAXS experiments that revealed aggregation numbers of 108 and 168 for ASB-14 and ASB-16 micelles, respectively. This study characterizes an interesting micelle system that can be used in the study of membrane proteins by solution NMR spectroscopy.     

Adsorption and micellar properties of a mixed system of nonionic-nonionic surfactants

We study the surface adsorption and bulk micellization of a mixed system of two nonionic surfactants, namely, ethylene glycol mono-n-dodecyl ether (C12E1) and tetraethylene glycol mono-n-tetradecyl ether (C14E4), at different mixing ratios at 15 degrees C. The pure C14E4 monolayer cannot show any indicative features of phase transition because of both hydration-induced and dipolar repulsive interactions between the bulky head groups. On the other hand, the monolayers of pure C12E1 and its mixture with C14E4 undergo a first-order phase transition, showing a variety of surface patterns in the coexistence region between the liquid expanded (LE) and liquid condensed (LC) phases under the same experimental conditions. For pure C12E1, the domains are of a fingering pattern while those for the C12E1/C14E4 mixed system are found to be compact circular and small irregular structures at 2:1 and 1:1 molar ratios, respectively. The critical micelle concentration (cmc) values of both the pure and the mixed systems were measured to understand the micellar behavior of the surfactants in the mixture. The cmc values of the mixed system were also calculated assuming ideal behavior of the surfactants in the mixture. The experimental and calculated values are found to be very close to each other, suggesting an almost ideal nature of mixing. The interaction parameters for mixed monolayer and micelle formation were calculated to understand the mutual behavior of the surfactants in the mixture. It is observed that the interaction parameters for mixed monolayer formation are more negative than those of micelle formation, indicating a stronger interaction between the surfactants during monolayer formation. It is concluded that since both the surfactants bear EO units in their head groups, structural parity and hydrogen bonding between the surfactants allow them to be closely packed during monolayer and micelle formation.     

Influence of ionic and nonionic hydrotropes on micellar behavior of a cationic gemini surfactant butanediyl-1,4-bis(dimethylcetylammonium bromide)

Micellization of binary systems of a cationic gemini surfactant butanediyl-1,4-bis(dimethylcetylammonium bromide) (16-4-16) and cationic/nonionic hydrotropes (aniline-hydrochloride, 2-methylanilinehydrochloride, 4-methylanilinehydrochloride, hydroxybenzene, 1,3-benzenediol, benzene-1,2,3-triol) have been studied using a conductometric technique. The critical micelle concentrations (cmc) for different mixing mole fractions at different temperatures have been calculated. To explain and compare the results, theoretical models of Clint, Rubingh and Motomura have been used to obtain the ideal cmc, mixed micelle composition, interaction parameters (β(m)), free energies of micellization, and activity coefficients. The mixtures show nonideal behavior and the interactions between the surfactants and the hydrotropes are synergistic in nature which is confirmed by high negative β(m) values and low values of the activity coefficients. Thermodynamic parameters were also obtained from the temperature dependence of the cmc values.     

Synthesis and Surface-Active Properties of New Photosensitive Surfactants Containing the Azobenzene Group

Several water-soluble cationic surfactants, 4-alkylazobenzene-4'-(oxy-2-hydroxypropyl)trimethylammonium methylsulfate (AZMS) (AZMS-0, AZMS-1, AZMS-2, AZMS-4, and AZMS-8), containing alkylglycidylether and azoarene have been synthesized with high yields of 63-78% and their surface-active properties have been investigated upon irradiation with UV/vis light. All of the trans-AZMS surfactants are isomerized to cis-trans mixtures containing 92.5% cis isomer by UV light irradiation at 350 nm. The cis isomers in the mixtures are reverted to trans isomers by visible light irradiation (lambda>445 nm). Such photoisomerization induces changes in the surface activity of each surfactant. The critical micelle concentration (cmc) of the trans form of AZMS-8 surfactant is about 1.28x10(-4) mol/l. At the photostationary state, 92.5% of the trans form is changed to the cis form which exhibits a slightly higher cmc (3.41x10(-4) mol/l). The new cmc of AZMS surfactants upon photoisomerization is similar to that of the ideal mixed micellar system. In particular, the ratio of cmc(cis) to cmc(trans) of AZMS derivatives is about 1.87-2.85 which increases proportionally with the chain length of alkyl group. The minimum average area per molecule (A(min)(a/w)) for the trans and cis isomers of AZMS-8 is 0.60 and 0.74 nm(2), respectively. The difference in the A(min)(a/w) may originate from the structural differences in the two isomers. These values are quite different as compared to those of the conventional azobenzene surfactants. Copyright 2000 Academic Press.     

Studies of mixed surfactant solutions of cationic dimeric (gemini) surfactant with nonionic surfactant C12E6 in aqueous medium

The interaction between the alkanediyl-alpha,omega-type cationic gemini surfactant, [(C(16)H(33)N(+)(CH(3))(2)(CH(2))(4)N(+)(CH(3))(2)C(16)H(33))2Br(-)], 16-4-16 and the conventional nonionic surfactant [CH(3)(CH(2))(10)CH(2)(OCH(2)CH(2))(6)OH], C(12)E(6) in aqueous medium has been investigated. The critical micelle concentrations of different mixtures have been measured by surface tension using a du Nouy tensiometer in aqueous solution at different temperatures (303, 308, and 313 K). Maximum surface excess (Gamma(max)) and minimum area per molecule (A(min)) were evaluated from a surface tension vs log(10)C (C is concentration) plot. The cmc value of the mixture was used to compute beta(m), the interaction parameter. The beta(sigma), the interaction parameter at the monolayer air-water interface, was also calculated. We observed synergism in 16-4-16/C(12)E(6) system at all concentration ratios. The micelle aggregation number (N(agg)) has been measured using a steady state fluorescence quenching method at a total surfactant concentration approximately 2 mM at 25 degrees C. The micropolarity and the binding constant (K(sv)) of mixed systems were determined from the ratio of intensity of peaks (I(1)/I(3)) of the pyrene fluorescence emission spectrum. The micellar interiors were found to be reasonably polar. We also found, using Maeda's concept, that the chain-chain interactions are very important in this system.     

C12-s-C12·2Br与低碳醇混合水溶液胶团化行为的温度效应和焓/熵补偿

季铵盐Gemini表面活性剂C12-s-C12·2Br(s=2,3,4,6)与丙醇、丁醇、戊醇、己醇混合水溶液的In(cmc)随温度升高而逐渐增大.计算所得热力学数据表明,C12-s-C12·2Br与醇混合胶团化过程服从熵驱动机理,也出现了焓/熵补偿现象.随着温度上升,熵驱动力增大,在指定温度时,醇分子烷烃链上碳原子数n增大使△Gm0值减小,胶团结构更加稳定;而增加s使值增大,胶团稳定性下降.     

新型脲基双子表面活性剂的合成及其性能

以N,N-二甲基-1,3-丙二胺、固体光气、溴代烷为原料合成了三种新型含脲基双子表面活性剂(LY-12、LY-14、LY-16),并通过1H NMR、ESI-MS和FT-IR表征了结构。测定了其Krafft点、乳化性能、起泡性能;通过测定表面张力γcmc以及不同温度下的临界胶束浓度(CMC)计算表面活性参数(Γmax、Amin、pc20)与热力学参数(ΔGmθ、ΔHmθ、ΔSmθ)。结果表明,LY-12、LY-14的Krafft点低于0℃,LY-16的Krafft点低于10℃;LY-12、LY-14、LY-16的乳化时间分别为173、275和338 s;LY-12的起泡性显著优于LY-14和LY-16;三种表面活性剂的表面张力γcmc分别为38. 77、37. 42和36. 59 m N/m;298. 15K条件下,其CMC值分别为0. 19、0. 15、0. 13 mmol/L。表面活性参数与热力学参数计算表明,三种表面活性剂均具有高的表面活性且胶束的形成是熵驱动的自发放热过程。     

Synthesis and surface properties of semi-fluorinated gemini surfactants with two reactive bromo pendant groups

This paper presents a series of semi-fluorinated gemini surfactants with two bromo pendant groups. It reviews the effect of the number of methylene units in the spacer group between the two hydrophilic quaternary ammonium heads. Critical micelle concentration (cmc) and free energy of micellization (ΔG(M)(0)) of the title surfactants, in aqueous solution, have been investigated as a function of the number n of carbon atoms in the hydrocarbon spacer. We have pointed out a different behaviour as compared to Gemini hydrocarbon homologues. In the present study, when the number of methylene units (n) in the spacer increases, the cmc first decreases and reaches an optimum for (n=6), then it increases linearly from n≥6. Variations of cmc have been interpreted in terms of conformation changes of the surfactant ion and progressive penetration of the alkyl chain spacer in the micelle hydrophobic core. In this series, the increase of the hydrophobicity seems not to favour the micellisation process as expected, probably impacted by the mutual phobicity of the perfluorinated tails and the hydrocarbon spacer. A minimum is reached for a spacer with six methylene units which seems to be the optimal conformation. The free energy of micellization (ΔG(M)(0)) confirm this tendency.     

Surface and bulk properties of aqueous decyltrimethylammonium bromide-hexadecyltrimethylammonium bromide mixed system

The aqueous mixed system decyltrimethylammonium bromide (C(10)TAB)-hexadecyltrimethylammonium bromide (C(16)TAB) was studied by conductivity, ion-selective electrodes, surface tension, and fluorescence spectroscopy techniques. The mixture critical micelle concentration, cmc(*), aggregation number, N( *), and micelle molar conductivity, Lambda(M)(cmc), showed that the system aggregation is strongly nonideal. Both cmc(*) and N( *) results were analyzed with two different procedures: (i) the regular solution theory on mixed micelles or Rubingh's theory, and (ii) by the determination of the partial critical micelle concentration of the amphiphile component i in the presence of a constant concentration of the other amphiphile component, cmc(i)( *). The Rubingh procedure gives micelles richer in C(16)TAB than the overall mixtures, while procedure (ii) gives micelles having the same composition as in the complete surfactant mixture (alpha(C(10)TAB). Mixed micelles are larger than pure surfactant ones, with nonspherical shape. Using a literature model, the cause of the synergistic effect seems to be a reduction of the hydrocarbon/water contact at the micelle surface when mixed micelles form. Conductivity and ion-selective electrodes indicate that highly ionized premicelles form immediately before the cmc(*). The air/solution interface is strongly nonideal and much richer in C(16)TAB than the composition in the bulk. When micelles form there is a strong desorption from the air/solution interface because micelles are energetically favored when compared with the monolayer.     

水溶液中两亲药物盐酸异丙嗪-表面活性剂体系的胶束化行为

The behavior of the mixed amphiphilic drug promethazine hydrochloride(PMT) and cationic as well as nonionic surfactants was studied by tensiometry.The cmc values of the PMT-surfactant systems decrease at a surfactant mole fraction of 0.1 and it then becomes constant.The critical micelle concentration(cmc) values are lower than the ideal cmc(cmc*) values for PMT/TX-100,PMT/TX-114,PMT/Tween 20,and PMT/Tween 60 systems.For the PMT/Tween 40,PMT/Tween 80,PMT/CPC,and PMT/CPB systems the cmc values are close to the cmc* values.This indicates that PMT forms mixed micelles with these surfactants by attractive interactions.The surface excess(Γmax) decreases in the presence of surfactants.The rigid structure of the drug makes adsorption easier and the contribution of the surfactant at the interface decreases.The interaction parameters βm(for the mixed micelles) and βσ(for the mixed monolayer) are negative indicating attraction among the mixed components.     

Complex formation in alkyldimethylamine oxide/sodium palmitate/water mixtures

The complex formation between nonionic alkyldimethylamine oxide (CnDMAO, n=14, 16, and 18) and sodium palmitate (NaPa) in the solid phase of CnDMAO/NaPa mixtures and the dependence of the interaction parameter beta of the regular solution theory (RST) on the mixed micelle composition of C16DMAO/NaPa mixtures were investigated. The dissolution temperature showed a maximum at a NaPa mole fraction X(Pa)(*) of 0.3-0.4 for C16DMAO/NaPa and 0.2 for C18DMAO/NaPa. The compositions of the complexes suggested by X(Pa)(*) are C16DMAO: NaPa=3:2 or 2:1 and C18DMAO:NaPa=4:1. The composition X(Pa)(*) depended on the chain length of the amine oxides. The maximum was not observed in the case of the C14DMAO/NaPa/water system. In the range 0.7< or =X(Pa)< or =1.0, dissolution temperature depression was observed with decreasing X(Pa). The dissolution temperature depression was analyzed by taking into account the nonideal behavior in the mixed micelles and the counterion binding on the mixed micelle surface. The negative beta values were obtained for all three mixed systems. It was shown that the counterion activity remained practically constant in the range of 0.7< or =X(Pa)< or =1.0. The cmc values of C16DMAO/NaPa mixtures were determined by pyrene fluorescence measurement. For C16DMAO/NaPa mixtures, the dependence of the RST interaction parameter beta on the mixed micelle composition X(Pa) was determined for a wide range (0.2< or =X(Pa) < or =0.9). In the range 0.2< or =X(Pa)< or =0.5, the beta values were obtained from an analysis of cmc based on the RST. In the range 0.7< or=X(Pa)< or=0.9, the beta values were obtained from an analysis of the dissolution temperature depression. From the analysis of the micelle composition dependence of the beta values, a short-range attractive interaction between the headgroup of C16DMAO and palmitate anion is suggested.