Mixed Micellization of Dodecyldimethylamine Oxide with Bile Salts in Aqueous Solutions

Micellar behavior of dodecyldimethylamine oxide (DMDAO) with bile salts [sodium deoxycholate (NaDC) and sodium cholate (NaC)] with and without NaCl was studied by surface tension. Interaction parameters of the mixed micelles were estimated using Rubingh's theory. Strong synergism observed for each mixed system, which is a common feature shown by anionic-cationic mixtures. The mixed solutions remained clear even at equimolar ratio. Different behavior of the two bile salts is explained on the basis of their orientation in cationic micelles.     

水杨酸钠对阳离子Gemini表面活性剂水溶液中蠕虫状胶束形成和性质的影响

用稳态和震荡剪切实验研究了水杨酸钠(NaSal)对50 mmol·L^-1阳离子Gemini表面活性剂2-羟基-(三亚甲基-α,ω-双十二烷基三甲基溴化铵和三亚甲基-α,ω-双十二烷基三甲基溴化铵, 简写为12-3(OH)-12和12-3-12)水溶液中形成蠕虫状胶束及其性质的影响. 在无盐状态下, 50 mmol·L^-1的12-3(OH)-12或12-3-12在水溶液中仅形成球状或棒状胶束. NaSal可促进上述两体系胶束的生长, 生成蠕虫状胶束. 比较而言, 12- 3(OH)-12对NaSal更敏感, 可以在低盐浓度下生成蠕虫状胶束. 而且与12-3-12体系相比, 12-3(OH)-12生成了更长的蠕虫状胶束. 这些差别在于12-3(OH)-12体系中存在羟基连接链之间的氢键作用, 这增加了12- 3(OH)-12头基的亲水性, 促进了反离子的解离, 增大的胶束表面电荷密度更强烈地结合水杨酸根反离子, 减小了头基间的静电斥力, 反过来又增强了分子间氢键, 致使 12-3(OH)-12胶束迅速生长.     

Dynamics of Micelles of Polyethyleneoxide-Polypropyleneoxide-Polyethyleneoxide Block Copolymers in Aqueous Solutions

The dynamics of the micelles of five triblock poly(ethyleneoxide)-poly(propyleneoxide)-poly(ethyleneoxide) copolymers, the Pluronics P104 (EO27PO61EO27), P84 (EO19PO43EO19), P65 (EO18PO29EO18), P85 (EO26PO40EO26), and P103 (EO17PO60EO17), have been investigated using two chemical relaxation methods: the temperature-jump and the ultrasonic relaxation (absorption). In the frequency range investigated (0.5-50 MHz), the ultrasonic absorption spectra (absorption vs frequency plots) consisted in tails of relaxation curves, indicating characteristic times much longer than 0.3 μs for the exchange of copolymers between micelles and intermicellar solution. Absorption measurements at a fixed frequency yielded the critical micellization temperature of the solutions. The temperature-jump results obtained in this study together with those from a previous one for the copolymers L64 (EO13PO30EO13) and PF80 (EO73PO27EO73) (B. Michels et al., Langmuir 13, 3111, 1997) showed that the relaxation time associated with the formation/breakup of micelles becomes longer upon increasing copolymer molecular weight at constant composition. This time also increased when decreasing the length of the hydrophilic block at fixed hydrophobic block length or increasing the length of the hydrophobic block at fixed hydrophilic block length, similar to conventional surfactants. The dynamics of block copolymers micelles in aqueous solution are discussed. Copyright 1999 Academic Press.     

生物相容性嵌段型聚电解质胶束在水溶液中的酶降解行为

采用激光光散射仪和原子力显微镜研究了生物相容性嵌段型聚电解质聚左旋乳酸-b-聚甲基丙烯酸二甲氨基乙酯(PLLA-b-PDMAEMA)胶束在水溶液中2个温度(室温25.0℃和人体温度36.8℃)和2个pH值(肿瘤pH=4.9和正常组织pH=7.4)条件下的酶降解行为. 酶降解过程中存在一个失活时间, 在此之前, 胶束的酶降解遵循逐个降解机理. 失活时间之后, 出现裂纹或是通道的胶束核为降低其在溶剂中的表面积, 从而降低体系自由能, 胶束之间发生了聚集. 升高温度后, 酶的活性提高, 初始降解速率加快. 由于pH=4.9时胶束壳层因静电斥力作用而较为伸展, 使得胶束降解更快.     

C9pPHCNa与C10TABr混合水溶液的表面吸附和胶团形成

羧酸盐Gemini表面活性剂C9pPHCNa与季铵盐表面活性剂十烷基三甲基溴化铵(C10TABr)混合水溶液的胶团生成能力、降低水表面张力的能力和效率均出现明显的增效. 当C9pPHCNa在溶液中的摩尔分数(α1)为0.33时，cmcT(临界胶团总浓度)、γcmc(临界胶团总浓度对应的表面张力)、c20,T(降低20 mN•m^-1水表面张力所需的表面活性剂总浓度)这3个指标均达到最低值，分别为0.60 mmol•L^-1、23.5 mN•m^-1和1.58×10^-5 mol•L^-1. 在所有考察的溶液比例范围内，二组分在混合胶团和表面吸附层中的组成均接近等摩尔比，表现出强烈的分子间相互作用.     

Fluorescence Probe Studies of Ionic Micelles in Concentrated Salt Solutions

We have investigated the effect of salt concentration and temperature on the average aggregation number and micro-polarity of the interior of micelles of sodium dodecyl sulfate (SDS). sodium tetradecyl sulfate (STDS) and lithium dodecyl sulfate (LiDS). The transient fluorescence decay of micelle-solubilized pyrene has been measured and analyzed. An exponent weighted average aggregation number <n>_e was obtained by this technique. For SDS and STDS in NaCl solution, <n>_e increases as the temperature is lowered or salt concentration is increased <n>_e increased from ～ 50 to ～ 250 over [NaCl] = 0 to 0.8 M. Due to the strong counterion binding of lithium in the micellar solution, the LiDS micelle is much, smaller and does not increase appreciabily even at [LiCl] =0.8 M. From the fluorescence spectrum fine structure of pyrene and the fluorescence decay of the monomer and excimer, we can understand the local polarity and the water penetration to the interior of the micelle upon addition of salts and with changing temperature. The interior of the micelle becomes more nonpolar as the salt concentration is increased and the temperature is lowered. A complete kinetic analysis of the time–dependence of the fluorescence is given. The kinetic analysis is in agreement with the results reached by fluorescence spectral analysis.     

Formation and Physicochemical Features of Hybrid Threadlike Micelles in Aqueous Solution

We investigate the construction of long, stable hybrid threadlike micelles consisting of polyelectrolytes and oppositely charged surfactants in aqueous solution and examine the physicochemical features such as their structure and viscoelastic behavior in aqueous solution. The most important point for their construction is the careful control of interactions, especially electrostatic interactions, caused between the surfactants and polyelectrolytes. Incorporated polyelectrolytes are fully extended in these hybrid threadlike micelles irrespective of the molecular weight of the polymer. The viscoelastic behavior of the hybrid threadlike micellar solution is similar to that of ordinary threadlike micellar systems consisting of low‐molecular‐weight substances. However, the inclusion of polymers in the micelles causes differences in their mechanical properties.     

十烷基硫酸钠-全氟辛酸钠混合表面活性剂在四氯乙烯-水界面上的吸附及胶团形成

测定了在30℃、总离子强度为0.1m时不同比例混合的十烷基硫酸钠(C₁₀SN_a)-全氟辛酸钠(7CFNa)在四氯乙烯-水界面的界面张力,研究混合溶液的界面性质及胶团形成,结果表明:(1)7CFNa与C₁₀SNa在混合溶液中,基本上各自独立形成胶团;(2)混合表面活性剂在四氯乙烯-水界面上的吸附与在正庚烷-水界面上吸附规律相同;(3)测定C₁₀SNa、7CFNa在不同油-水界面上的界面张力,证实碳氟链与碳氯链之间具有“互憎性”。     

Cholesterol Binding to Simple Micelles in Aqueous Bile-Salt–Cholesterol Solutions

The true thermodynamic activity (A_T) of cholesterol (Ch) in aqueous solutions containing taurocholate (TC)–Ch was determined by employing a direct assay of a 1 × 2-cm silicone polymer film with 0.025 cm thickness. Using theA_Tdata, information on the nature of micellar species present in the TC–Ch system, and employing a binding-site model previously developed for tauroursodeoxycholate (TUDC)–Ch and taurochenodeoxycholate (TCDC)–Ch systems, it appeared that the Ch-binding affinity for simple bile-salt micelles corresponds precisely with the order of hydrophobicity, TUDC < TC < TCDC. Further, although simple TC micelles and simple TCDC micelles have similar binding capacities, the first Ch binding to a simple TC micelle may not significantly facilitate the second Ch binding, as occurs in simple TCDC micelles. For TUDC–Ch, TC–Ch, and TCDC–Ch systems, the concentration of bound simple micelles increased with increasingA_Tvalues, whereas the unbound simple micelle concentration decreased proportionally. These results provide insights into the possible influence of bile-salt species on Ch-binding to simple micelles in bile-salt–Ch solutions.     

C9pPHCNa与C10TABr混合水溶液的表面吸附和胶团形成

羧酸盐Gemini表面活性剂C9pPHCNa与季铵盐表面活性剂十烷基三甲基溴化铵(C10TABr)混合水溶液的胶团生成能力、降低水表面张力的能力和效率均出现明显的增效.当C9pPHCNa在溶液中的摩尔分数(α1)为0.33时,cmcT(临界胶团总浓度)、γcmc(临界胶团总浓度对应的表面张力)、c20,T(降低20mN·m-1水表面张力所需的表面活性剂总浓度)这3个指标均达到最低值,分别为0.60mmo·lL-1、23.5mN·m-1和1.58×10-5mol·L-1.在所有考察的溶液比例范围内,二组分在混合胶团和表面吸附层中的组成均接近等摩尔比,表现出强烈的分子间相互作用.     

介观模拟方法研究高分子表面活性剂在水介质中的聚集行为

高分子表面活性剂已广泛应用于许多领域, 其构型复杂、分子量大等特点使其聚集行为不同于小分子表面活性剂. 从微观上认识其聚集行为可为应用提供指导, 因而此方面的研究倍受关注. 计算机模拟技术的发展使我们能成功地在微观或介观水平上获得高分子表面活性剂聚集行为的信息. 本文综述了耗散粒子动力学(DPD)和介观动力学(MesoDyn)在高分子表面活性剂聚集行为研究中的应用. 着重介绍了这两种介观模拟方法研究单一高分子表面活性剂溶液的相行为及其与低分子表面活性剂之间的相互作用, 揭示了实验中难以观测的微观相分离及聚集体结构形态的变化规律. 这些信息可以为实验研究提供指导和补充.     

Interaction Mechanisms Between Anionic Surfactant Micelles and Different Metal Ions in Aqueous Solutions

In its using or eliminating processes, surfactant solutions usually exhibit different behaviors because of the different species or concentrations of the encountered metal ions. Interactions between anionic surfactant (SDS) micellar solutions and several familiar metal salt solutions (Al₂(SO₄)₃, FeCl₃, CaCl₂ and MgCl₂) were investigated. Precipitates were formed in all systems except SDS‐MgCl₂ visually. Stoichiometric analysis reveals that, in SDS‐Al₂(SO₄)₃ system, the precipitation phenomenon is mainly owing to the effect of adsorption‐charge neutralization between Al³⁺ ions and SDS micelles; in SDS‐FeCl₃ system, bridge connection effect of Fe(OH)²⁺ ions among SDS micelles becomes the dominant mechanism; while in SDS‐CaCl₂ system, all SDS micelles are decomposed and solubility product of Ca(DS)₂ crystal results in the precipitation. SEM photographs of the precipitates can serve as additional vivid proofs of the above conclusion.     

正负离子表面活性剂与非离子表面活性剂混合水溶液的相互作用

非离子表面活性剂的加溶作用有助于正负离子表面活性剂的溶解,在恰当比例时,能基本保持其表面活性;正负离子表面活性剂与非离子表面活性剂之间的相互作用很弱,容易形成接近“理想”的混合胶团;恒定非离子表面活性剂浓度时,随正负离子表面活性剂浓度增加,溶液的浊点也增加;超过临界胶团浓度后浊点下降。     

Swellability of ASMOL Protective Coating in Water and Aqueous Salt Solutions

The swellability of a new material for protective coatings, ASMOL (asphalt-resin oligomer), in water and aqueous salt solutions was studied gravimetrically and by thermogravimetric analysis.     

Clouding and Hydrodynamic Behavior of Pluronic-Surfactant Interaction in Aqueous Salt Solutions

Clouding behavior of PEO-PPO-PEO and PPO-PEO-PPO block copolymers were studied in presence of sodium dodecyl sulfate (SDS) and NaCl. Extensive study of Pluronic P84 (EO₁₉PO₄₃EO₁₉) with different salts and ionic surfactants, were carried out using cloud point, viscosity and dynamic light scattering (DLS) measurements. The change in cloud point, as well as the size of P84 micelles in aqueous salt solution obeys the Hofmeister lyotropic series. Results on P84-ionic surfactant mixture indicate stronger interaction in case of SDS compared to those in presence of dodecyl trimethylammonium chloride (DTAC); here interaction seems to diminish in the presence of salts.     

Freezing and Hydrate Formation in Aqueous Sodium Perchlorate Solutions

The determination of the phase diagram of the binary system sodium perchlorate – water is reported. Beside the eutectic point, two polymorph crystal structures of sodium perchlorate dihydrate were determined. The two crystal structures are discussed, compared to each other and to other known sodiumhalide dihydrate crystal structures. The two polymorphs of the perchlorate dihydrate represent the two variants of connected octahedra in the layer structure found for sodium halide dihydrates.     

Quasi-thermodynamics of Viscous Flow of Electrolyte Solutions in Aqueous, Non-aqueous and Mixed Aqueous Solvents

Viscosity B-coefficients for cesium chloride and lithium sulfate in methanol + water mixtures at 25 and 35 °C are reported. A general treatment of the quasi-thermodynamics of viscous flow of electrolyte solutions is described. ΔG ₃ ^Θ (1→1′), the contribution made to the Gibbs energy of activation of the solution by the influence of the solute on the solvent, is a function of solute–solvent interactions only; but, ΔH ₃ ^Θ (1→1′) and ΔS ₃ ^Θ (1→1′) also reflect the solvent–solvent interactions. In aqueous solution all alkali-metal ions except Li⁺ are sterically unsaturated, having solvent co-ordination numbers n<n _max, the maximum allowed sterically. Such complexes exchange molecules with the solvent more readily than saturated ones and have energy–reaction co-ordinate diagrams in forms that explain the negative B or ΔG ₃ ^Θ (1→1′) values found in aqueous solution. Saturated complexes are the norm in non-aqueous solvents, and the ΔG ₃ ^Θ (1→1′) values are determined mainly by the secondary solvation. Behavior in mixed solvents reflects the transition from aqueous to non-aqueous behavior across the range of solvent composition.     

Shape and Structure Formation of Mixed Nonionic–Anionic Surfactant Micelles

Aqueous solutions of a nonionic surfactant (either Tween20 or BrijL23) and an anionic surfactant (sodium dodecyl sulfate, SDS) are investigated, using small-angle neutron scattering (SANS). SANS spectra are analysed by using a core-shell model to describe the form factor of self-assembled surfactant micelles; the intermicellar interactions are modelled by using a hard-sphere Percus–Yevick (HS-PY) or a rescaled mean spherical approximation (RMSA) structure factor. Choosing these specific nonionic surfactants allows for comparison of the effect of branched (Tween20) and linear (BrijL23) surfactant headgroups, both constituted of poly-ethylene oxide (PEO) groups. The nonionic–anionic surfactant mixtures are studied at various concentrations up to highly concentrated samples (ϕ ≲ 0.45) and various mixing ratios, from pure nonionic to pure anionic surfactant solutions. The scattering data reveal the formation of mixed micelles already at concentrations below the critical micelle concentration of SDS. At higher volume fractions, excluded volume effects dominate the intermicellar structuring, even for charged micelles. In consequence, at high volume fractions, the intermicellar structuring is the same for charged and uncharged micelles. At all mixing ratios, almost spherical mixed micelles form. This offers the opportunity to create a system of colloidal particles with a variable surface charge. This excludes only roughly equimolar mixing ratios (X≈ 0.4–0.6) at which the micelles significantly increase in size and ellipticity due to specific sulfate–EO interactions.     

Wormlike Micelle Formation and Rheological Behavior in the Aqueous Solutions of Mixed Sulfate Gemini Surfactant without Spacer Group and Dodecyltrimethylammonium Bromide

The rheological behavior of the aqueous solutions of mixed sulfate gemini surfactant with no spacer group, referred to as d‐C₁₂S, and dodecyltrimethylammonium bromide (C₁₂TABr) at a total concentration of 100 mmol·L⁻¹ but different molar ratios of C₁₂TABr to d‐C₁₂S (α₁) was investigated using steady rate and frequency sweep measurements. The wormlike micelles were formed over a narrow α₁ range of 0.20–0.27. The viscoelastic solutions exhibited Maxwell fluid behavior. At the optimum molar ratio of 0.25, the zero‐shear viscosity was as high as 600 Pa·s and the length of the mixed wormlike micelle was about 0.45–0.85 µm. The present result provides an example to construct long wormlike micelles by anionic gemini surfactant.     

Polymorphism of Micelles in Aqueous Cetyltrimethylammonium Bromide Solutions

A viscometric study was made of the polymorphous transformation of micelles in an aqueous solution of cetyltrimethylammonium bromide in the presence of NaBr and sodium methylbenzenesulfonate. The effects of temperature and nature and concentration of additives on the second critical micelle concentration were studied. The thermodynamic characteristics of the micellar transition are estimated.