Transport characteristics of microemulsions

The dependence of transport characteristics (kinematic viscosity, conductivity, diffusion coefficient) of microemulsions in the octane/water/pentanol/sodium dodecyl sulfate system on the volume fraction of water () was studied by viscosimetry, conductometry, and photon correlation spectroscopy The percolation character of the specific conductivity of microemulsions is revealed; the conductivity and geometrical percolation thresholds are determined. The known percolation models of microemulsions and the dependence of the specific conductivity on the most probable dimension of microdrops are discussed. A cellular model of the microemulsion studied is proposed and its validity is shown in the region of comparatively low values above the conductivity percolation threshold.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1521–1528, September, 1993.     

Middle-phase microemulsions of green surfactant alkyl polyglucosides

Microemulsions are important organized molecular assembles in surfactant solutions and are used in various fields such as tertiary oil recovery, pharmaceutics, cosmetics, nanoparticle synthe-sis and chemical engineering. The more commonly used nonionic surfactants to produce micro- emulsions are the ethylene oxide-based compounds (CiEj). In recent years alkyl polyglucosides have been received considerable attention in producing microemulsions[17]. Alkyl polyglucosides (APG), which are widely…     

A nucleophilic substitution reaction in microemulsions based on either an alcohol ethoxylate or a sugar surfactant

A nucleophilic substitution reaction between 4-tert-butylbenzyl bromide and a series of iodide salts has been performed in oil-in-water microemulsions based on either a fatty alcohol ethoxylate or a sugar surfactant. The reaction kinetics was compared with the kinetics of the same reaction performed in a microhomogeneous reaction medium, d-MeOH. Previous results showing a particularly high reactivity in the microemulsion based on the fatty alcohol ethoxylate was confirmed. It was shown that in both microemulsions the reaction rate was almost independent of the choice of counterion to iodide. This indicates that complexation of the cation with the surfactant headgroup, which, in particular, could have taken place with surfactants containing oligooxyethylene chains (a “crown ether effect”), seems not to be of importance.

¹²⁷I NMR studies, as well as quadrupole splitting experiments performed by ²H NMR, indicate that there is a certain accumulation of iodide at the oil–water interface of the microemulsions. It is difficult to draw any quantitative conclusions in this respect, however.

The results obtained in this study, combined with results from previous investigations of the same reaction, indicate that the unexpectedly high reactivity obtained in the microemulsion based on a surfactant containing an oligooxyethylene headgroup is most probably due to the nucleophile being poorly solvated when present in the headgroup layer of such a microemulsion. Poorly solvated anions are known to be highly reactive nucleophiles.     

微乳胶粒的形成与表面活性剂的作用——粗粒化力场分子动力学模拟研究

从微观机理上研究表面活性剂对微乳胶粒形成的影响有利于推动微乳状液在各个领域的应用研究．本文采用分子动力学模拟方法研究了微乳胶粒的形成过程及表面活性剂对微乳胶粒形成的影响．正十二烷（C12H26）和十二烷基硫酸钠（SDS）作为油分子和表面活性剂分子的模型,Martini粗粒化（coarse．grained,CG）力场描述分子间和分子内的相互作用,对含有不同浓度的正十二烷和表面活性剂的12个模型分别进行了100ns的分子动力学模拟．模拟结果显示,不含表面活性剂的体系迅速发生水油相分离,且分离过程伴随着势能的明显下降;含有表面活性剂的体系中,在相同时间内通过模拟得到了稳定的、表面活性剂分子包裹油分子的胶粒．对不同温度下模拟得到的数据分析发现,胶粒形成初期的动力学特征可以近似地表达为二级反应,聚集活化能为14．6kJ／mol．     

非离子表面活性剂TWeen80相图的研究

本文研究了醇类（正丁醇、正戊醇、正辛醇和正癸醇）、油类（正十八烷、正十六烷、正十四烷、正十烷、正癸烷和正辛烷）、正十八烷含量以及NaCl浓度对Tween80／醇／油／水体系相图的影响。结果表明，NaCl浓度对Tween80／正辛醇／正十八烷／水体系相图的影响不明显；醇类随着炭原子数目的增加，O／W微乳液区面积增大，W／O微乳液区面积减小，微乳液区总面积增大；不同的油类形成的微乳液区面积由大到小的顺序是：正十六烷≈正十四烷＞正十二烷＞正癸烷＞正十八烷＞正辛烷；随着正十八烷含量的增加，微乳区面积减小。用2277热活性检测系统测定了石油菌B－2分别在非微乳液和助表面活性剂分别是正戊醇、正辛醇，油是正十八烷所形成的微乳液中生长的功率－时间曲线。结果表明微乳液培养基更适用于B－2利用高碳烷烃进行生长；正辛醇作助表面活性剂形成的微乳液培养基比正戊醇作助表面活性剂形成的微乳液培养更为有利；O／W型微乳液比W／O型微乳液对B－2的生长更为有利。     

红外光谱研究以非离子型表面活性剂所组成微乳液的水结构

由烷基聚氧乙烯醚(AEO9)/正己醇/正十六烷/水所组成的微乳液,采用红外光谱对水内核的微观结构进行研究。以水分子的OH伸缩振动谱带, 由高斯分布曲线面积得出不同结构水的含量。只有少量水与表面活性剂结合, 另有部分水束缚于聚氧乙烯链段之间, 这些水与水相中的自由水呈动态平衡。当体系在剧烈振动后, 少量结合水转为束缚水, 静止后又恢复原状。     

Catalytic hydrolysis of phosphate esters in microemulsions

We have continued our kinetics investigation of the iodosobenzoate (IBA) catalysis of the hydrolysis of p-nitrophenyl diphenyl phosphate (PNDP), in microemulsion media composed of hexadecane in water stabilized by cetyltrimethylammonium bromide and 1-butanol over a range of water mass fractions. We have examined two iodosobenzoic acid derivatives (5-nitro-2-iodosobenzoic acid and 5-octyloxy-2-iodosobenzoic acid) as catalysts. In addition, we have determined by³¹P FT-NMR techniques that the major product of the hydrolysis of PNDP, both in IBA catalyzed and in uncatalyzed media, is diphenylphosphate.     

一种新型有机硅表面活性剂提高药液润湿性能的研究

研究了w(阿维菌素)=3%微乳剂,w(仲丁威)=15%微乳剂稀释液在一种含葡萄糖酰胺基的有机硅表面活性剂存在时的表面张力和接触角。对于阿维菌素微乳剂稀释液,当有机硅表面活性剂质量分数由0增加到0.0014%时,表面张力由32.4mN/m迅速降低到20.4mN/m。对于仲丁威微乳剂稀释液,当有机硅表面活性剂质量分数由0增加到0.014%时,表面张力由30.4 mN/m迅速降低到22.1mN/m,之后继续增加有机硅表面活性剂质量分数,表面张力基本不变。阿维菌素微乳剂稀释液接触小麦叶面瞬间的接触角(95°),比在梨树叶面的接触角(64°)高。稀释液在植物叶面的接触角随时间的推移和有机硅表面活性剂质量分数的增加而减小,并且稀释液在梨树叶面比小麦叶面润湿铺展快得多。     

Mechanism of Electrical Percolation of w/o Microemulsions Formed by Nonionic Surfactants

A study was carried out on the mechanism of electrical conductivity percolation of H₂O/C₁₆EO₂₀/n-butanol/heptane microemulsions. Electrical conductivity, UV-vis spectroscopy and FTIR spectra were used to study the diluted “dry” microemulsions with the mass ratio of C₁₆EO₂₀/n-butanol/heptane = 3:3:4. The results of electrical conductivity showed that the percolation occurred around φ_w = 20 wt% and the transition of w/o microemulsions to bicontinueous microemulsions happened when φ_w = 45 wt%. From the UV-vis absorption spectra, it was found that the absorption of methyl orange (MO) in microemulsions shifted red than that of in oil phase, but the maximal absorption peak (λ_max) remained unchanged when φ_w > 20 wt%. It implied that the position of MO solubilized in microemulsions was unvaried after free water appeared in the core. FTIR spectra revealed that the OH band of water in microemulsions moved to high frequency at low φ_w (< 20 wt%) and became broader at high φ_w. It indicated that the added water only caused the hydration of EO at low φ_w, the hydration completed when φ_w > 20 wt% and then the residual water entered into the core with properties similar to bulk water. The presence of free water as ions exchange medium will cause the electrical conductance increased. The percolation appeared after the hydration of EO completed.     

New anionic gemini surfactant based on EDTA accessible by convenient synthesis

A straightforward, broadly applicable synthetic strategy to anionic dimeric (“gemini”) surfactants is demonstrated, reacting ethylenediamine tetraacetic acid (EDTA) dianhydride with fatty amines. Characteristic surfactant properties in water are examined for the model compound based on N-methyldodecylamine. The new dimeric surfactant exhibits a low value for the critical micellization concentration (cmc < 10⁻⁴ mM), low surface tension at the cmc, and an enhanced solubilization capacity in comparison with a monomeric reference surfactant, sodium laurate. In particular, solutions of the gemini surfactant are remarkably stable in hard water, compared to conventional carboxylate surfactants.     

微乳凝胶中小分子传质研究

微乳凝胶中小分子传质研究对于拓宽胶束酶学研究内涵、加速酶在生物合成与转化领域中的应用、研制高性能生物传感器等具有重要理论意义和潜在应用价值.以微乳液中二价金属离子与紫脲酸胺之间的配位反应为指示反应,采用分光光度技术,研究了金属离子在由阳离子表面活性剂十六烷基三甲基溴化胺构建的微乳凝胶中的传质问题.结果表明,在由含紫脲酸胺微乳液及含金属离子微乳凝胶构成的体系中,金属离子在微乳凝胶中的传质是金属离子与紫脲酸胺配位反应的限速步骤.为进一步证实上述结论,还对影响金属离子在微乳凝胶中传质的各种因素(如微乳液中水与表面活性剂的摩尔比值、分散相中甘油与水的配比等)进行了研究,结果也证实了上述结论.     

Characteristics of ternary clove/water/1-butanol microemulsions based drug delivery system for aspirin

This work was intended to characterize aspirin solubilized in microemulsion systems comprising clove oil, 1-butanol and water. Microemulsions demonstrated the unique ability to solubilize aspirin in polar media, thus having good potential in drug delivery. After incorporation of aspirin, four samples were selected in microstructure and be investigated by conductivity measurements, transmission electron microscope (TEM), and spectroscopic studies (¹H-NMR, UV-visible spectroscopy, and IR spectra). The percolation behavior with variation of weight fraction of aqueous phase (?) was confirmed by conductivity measurements. In order to study the effect of aspirin, the conductivity results of aspirin-loaded samples were compared with non-loaded ones. The proton transfer and The competitive H-bonding interactions between aspirin with butanol and water were also discussed in details using ¹H-NMR, UV-visible spectroscopy, and IR spectra. These measurements confirmed that the hydrogen-bonded ion pair structure dominated in the solutions.     

Influence of 1-decanol on the surface tension and wetting power of a new anionic surfactant derived from sugar

We studied the adsorption behaviour at the liquid/air and liquid/solid interface of a new anionic surfactant derived from sugar, the sodium decyl galacturonate. The surface tension of aqueous solutions, measured in equilibrium and as a function of time, is particularly affected by the presence of decanol, synthesis residue, which amount ranges between about 0 and 13%. The surface tension lowering is accelerated in presence of decanol, owing to its rapid diffusion to the interface or/and because it affects the mobility and adsorption process of the anionic surfactant molecules. The wetting power of surfactant solutions were also investigated in relation with textile treatment applications. We measured the kinetics of absorption of surfactant solutions in a piece of standard cotton and compared it to the absorption of pure decanol, a completely wetting liquid and to the absorption of an alkylpolyglucoside. The time at which the fabric piece is saturated appears to be related to the adsorption of surface-active molecules on the fibers at the advancing liquid front/fabric contact line. Decanol was found to promote absorption and micellar life-time seem to reflect the differences observed at high concentration. This study shows the importance of controlling the amount of surface-active residues which may alter the kinetics of surfactant adsorption, particularly in industrial processes where equilibrium conditions are not reached.     

Dielectric analysis on phase transition and micelle shape of polyoxyethylene trisiloxane surfactant in dilute aqueous solution

The cloudy Silwet L-77 aqueous solution on the concentration range from 0.5%to 50%was investigated by dielectric relaxation spectroscopy.The concentration dependence of phase microstructure was confirmed by means of analyzing the dielectric parameters of bulk solution.The relaxation behavior was assigned to the interfacial polarization between the micelle and the medium,and the relaxation distribution parameter was used to figure the shape transition from sphere to ellipsoid with the concentration increasing.The synchronous reduction of permittivity and conductivity indicated the formation of the lamellar phase. As compensation,the quantity of the surfactant liquid phase gradually decreased,whose shape constantly kept ellipsoidal.     

Surface and fluorescence properties of a novel fluorescent surfactant

A novel kind of fluorescent surfactant having 7-hydroxylcoumarin group in the long alkyl chain was synthesized. The critical micelle concentration (CMC), surface tension (γ_cmc) at CMC and absorption, fluorescence properties of this product were determined. From the variations of fluorescence spectra in different solvents, it is observed that the polarity and dielectric constant of the solvents play important roles in the maximum fluorescence intensity and wavelength. Moreover, the surprised exhibition of two fluorescence bands in neutral and alkaline solutions has been attributed to the superexciplex formation of the product molecules. Also, the lower product concentration measuring the fluorescence properties as well as the supposed configuration of hydrogen bond of the product indicate that the larger aggregations cannot exist in alkaline solutions. The superexciplex is a possibility with two or more polar excited molecules together to form an excited state association.     

pH和盐类对非离子型表面活性剂所组成微乳液的异常流变性影响

以非离子型表面活性剂AEO~9、正十六烷、正己醇和水所组成的微乳液为对象, 研究盐和pH值对其粘度和流变性的影响, 得出它们在pH值为7时最小, 以及二价盐影响最大的结论, 正好与离子型微乳液结果相反, 为此进行了讨论。并从热效应和电导对其微观结构作了初步探索。     

含酰胺键的吡啶双子表面活性剂合成及性能

以间苯二甲酰氯、氨基吡啶、氯乙酰氯和长链伯胺(n为8、12、14、16)为原料,通过酰胺化反应合成了1,3-二[N-(3-吡啶基)]苯甲酰胺(中间体A)和N-烷基-2-氯乙酰胺(中间体B)。中间体A和中间体B通过季铵化反应,合成目标产物(I₈,I₁₂,I₁₄,I₁₆)。利用¹H-NMR、FTIR对产物及中间体结构进行表征。通过电导率法测定了目标产物在25℃、35℃、45℃的临界胶束浓度(CMC),进行热力学参数计算。用吊环法测定了25℃时目标产物的表面张力γ,计算了相关的表面性能参数。测定目标产物在25℃下的稳泡性及乳化能力。结果表明,合成表面活性剂具有良好的表面活性、稳泡性和乳化能力。     

全氟壬烯氧基苯磺酸钠/辛基酚聚氧乙烯醚-10复配体系的铺展性能

分析全氟壬烯氧基苯磺酸钠(OBS)与辛基酚聚氧乙烯醚-10(OP-10)复配比例对溶液的表面张力、油/水界面张力及铺展性能的影响,寻求最佳复配比例和最佳铺展浓度.研究结果表明,OBS/OP-10混合水溶液与OBS单一组分水溶液相比,表面张力略有增加,界面张力显著降低,因此混合水溶液的铺展性能显著改善,原来在环己烷上不铺展,复配后变得铺展.尤其以质量比为1∶3,浓度为3.12 mmol/L体系水溶液的铺展性能最好,可以在环己烷上快速铺展,而且显著降低了OBS的用量,约降低了67％ OBS用量,提高了经济效益.同时对OBS/OP-10不同复配比例的水溶液最佳铺展浓度进行了研究,发现由表面张力确定的临界胶束浓度、界面张力确定的临界胶束浓度并非最佳铺展浓度,三者之间有一定偏差,其中,最佳铺展浓度介于表面临界胶束浓度、界面临界胶束浓度之间,差额取决于氟碳表面活性剂和碳氢表面活性剂的性质及配比.