电导率法测定表面活性剂的临界胶束浓度

电导率法测定表面活性剂的临界胶束浓度邹耀洪（常熟高等专科学校化学系江苏２１５５００）物化实验中测定表面活性剂临界胶束浓度（ＣＭＣ）常用表面张力法［１］，但精确测定表面活性剂水溶液的表面张力受到一些限制，如毛细管升高法中要准确地测定毛细管的半径、溶液的...     

十五烷基芳基磺酸钠溶液表面性质的影响因素研究

测定了自制的四种高纯度十五烷基间二甲苯磺酸钠在纯水溶液和0.0393 mol/L异丙醇溶液中的表面性质,结果表明,随芳基向碳链中间位置的移动,临界胶束浓度cmc增大,分子极限占有面积Amin增大,标准吸附自由能 变得更负,降低表面张力的效率pc20增强,饱和吸附量Γ_max降低,临界胶束浓度时的表面张力γ_cmc降低;且异丙醇的加入使磺酸钠溶液的临界胶束浓度显著降低。从分子结构的特点探讨了分子支化程度对表面性能的影响。     

十四烷基芳基磺酸盐形成的分子有序组合体

以表面张力法、碘光谱法、水增溶法和相态图法研究了自制的三种十四烷基芳基磺酸盐在不同条件下形成的分子有序组合体(胶束、反胶束和微乳液),并考察了分子结构、溶剂、无机盐和短链醇等对其的影响.结果表明:增加十四烷基芳基磺酸盐分子亲油基支化度,不利于其在水溶液或混合极性溶剂(乙二醇-水)中形成胶束而有利于其在非极性溶剂正庚烷中形成反胶束;溶剂极性的降低,促使表面活性剂溶液由胶束溶液→单体溶液→反胶束溶液转变;无机盐或短链醇的加入促进了水溶液中胶束的形成,且反离子价态数或醇烷基碳原子数越大,越有利于胶束形成;无机盐浓度的增加导致表面活性剂/正丁醇/正辛烷/NaCl/水形成的微乳液体系在一定温度下发生由WinsorI→WinsorIII→WinsorII型的转变.     

乙二亚甲基-双（十六烷基二甲基溴化铵）稀水溶液的特性

合成并表征了阳离子Gemini表面活性剂乙二亚甲基-α,β-双（十六烷基二甲基溴化铵）（16-2-16）.用表面张力和粘度法确定了其cmc，通过表面张力曲线计算了16-2-16的表面吸附量、吸附分子面积和胶束形成自由能；并用悬滴法测定了16-2-16在空气表面和十二烷界面的动态表（界）面张力.用改进的Washburn方法测定16-2-16水溶液在硅胶粉末表面的接触角，并进一步讨论了16-2-16在硅胶表面的吸附引起的润湿性变化. 探讨润湿性变化与动态张力的关系. 将16-2-16 与溴代十六烷基三甲胺(CTAB)做比较:两种物质在含油硅胶粉末上引起的最高脱油率（实验室模拟驱油）均发生在cmc附近,但16-2-16的最高脱油率是68％， CTAB的是63％.而所用CTAB的cmc比16-2-16的约大50倍,也就是说用16-2-16可以获得更高的脱油率.     

全氟辛酸钠与十二烷基三甲基溴化铵混合胶束微环境性质的NMR, ESR研究

应用表面张力法、NMR法和ESR法研究了全氟辛酸钠(SPFO)-十二烷基三甲基溴化铵(DTAB)混合体系水溶液胶束形成及混合胶束的微环境性质(微观粘度、微观极性等).结果表明,碳氟表面活性剂碳氟链和碳氢表面活性剂碳氢链之间具有强烈的相互作用,DTAB与SPFO在水溶液中形成混合胶束.DTAB与SPFO混合体系的表面活性高于单一的DTAB或SPFO,混合体系cmc较单一的DTAB和SPFO低.DTAB与SPFO混合胶束的微观粘度较DTAB胶束的大,而微观极性较DTAB的小.     

胶束催化作用下实现聚苯乙烯的氯甲基化

用紫外分光光度法测定了离子型表面活性剂胶束溶液对聚苯乙烯四氯化碳溶液的增溶性能; 用胶束催化法实现了聚苯乙烯的氯甲基化, 用红外光谱法和佛尔哈德法表征了氯甲基化聚苯乙烯的化学结构与组成; 通过比较阴、 阳离子表面活性剂及结构不同的阳离子表面活性剂的催化效果, 探索了胶束催化的作用机理, 考察了表面活性剂结构对催化作用的影响规律. 结果表明, 表面活性剂胶束溶液可增溶聚苯乙烯的四氯化碳溶液, 随着四氯化碳在胶束中的增溶, 聚苯乙烯可转移至表面活性剂的胶束中; 胶束催化是实现聚苯乙烯的氯甲基化的有效途经, 仅用3.35 g/L的十六甲基三甲基溴化铵(CTAB),  于65 ℃， 5 h内即可使聚苯乙烯大分子链中的苯环氯甲基化程度达到37%; 聚苯乙烯与甲醛、 氯化氢的反应过程由亲电取代和亲核取代串联而成, 阳离子表面活性剂比阴离子表面活性剂的催化作用更加有效, 说明亲核取代是慢步骤; 阳离子表面活性剂疏水链越长, 对聚苯乙烯的增溶效果越好, 催化作用越强.     

丙烯酰胺型阴离子表面活性单体的化学结构与其胶束化行为

对两种丙烯酰胺型阴离子表面活性单体(2-丙烯酰胺基十四烷磺酸钠, NaAMC₁₄S; 2-丙烯酰胺基十二烷磺酸钠, NaAMC₁₂S)的化学结构与胶束化行为的关系进行了较深入的研究. 使用紫外分光光度法测定了NaAMC₁₄S, NaAMC₁₂S及十二烷基磺酸钠(SDS)在水中的溶解度, 同时采用表面张力法(环法)测定了它们在不同温度下的临界胶束浓度CMC; 采用稳态荧光探针法测定了不同浓度的胶束聚集数与本征胶束聚集数. 实验结果表明, 与普通表面活性剂相比, 由于丙烯酰胺型阴离子表面活性单体分子中具有两个亲水头基, 在水中的溶解性能较强, 故具有较低的Krafft温度; 在溶液表面的饱和吸附量低, 故降低水表面张力的能力较差, 即表面活性差; 疏水缔合的胶团较为疏松, 故聚集数很小; 胶束内分子间的疏水相互作用较弱, 故临界胶束浓度CMC较高.     

不同添加物对表面活性剂溶液预胶束形成的影响

关于表面活性剂溶液中预胶束的形成问题已有不少报道［’－‘］．预胶束是表面活性剂溶液在浓度很稀时（远小于其临界胶束浓度（CMC》、表面活性分子所形成的一种集合体·由于一般的物理化学方法对其难于捡出，因此常被研究者忽略．文献间曾指出：预胶束形成的驱动力与胶束一样，也是疏水作用所致．因此表面活性分子的链长、头部极性、溶剂性质以及添加物的引入等因素必然会影响预胶束的形成．本工作是对添加物的引入问题所作的初步研究·。作中所研究的阴离子表面活性剂有十二烷基硫酸钠（sss）·＋”烷基；Iv酸钠（5％）和十六烷基硫酸…     

全氟辛酸钠与十二烷基三甲基溴化铵混合胶束微环境性质的NMR,ESR研究

应用表面张力法、NMR法和ESR法研究了全氟辛酸钠(SPFO)-十二烷基三甲基溴化铵(DTAB)混合体系水溶液胶束形成及混合胶束的微环境性质(微观粘度、微观极性等)。结果表明, 碳氟表面活性剂碳氟链和碳氢表面活性剂碳氢链之间具有强烈的相互作用, DTAB与SPFO在水溶液中形成混合胶束。DTAB与SPFO混合体系的表面活性高于单一的DTAB或SPFO, 混合体系cmc较单一的DTAB和SPFO低。DTAB与SPFO混合胶束的微观粘度较DTAB胶束的大, 而微观极性较DTAB的小。     

表面活性单体AMC14AB在水溶液中的聚合动力学研究

采用溴酸钾-溴化钾法研究了阳离子型表面活性单体(2-丙烯酰胺基)乙基十四烷基二甲基溴化铵(AMC14AB)在水溶液中的聚合动力学,分别考察了引发剂浓度与单体浓度对聚合速率的影响,确定了聚合速率方程,分析了聚合机理,考察了温度对聚合反应的影响,测定了聚合表观活化能。研究结果表明,由于AMC14AB在水溶液中的胶束化行为,使其具有较快的聚合速率,于60℃下聚合,40min内转化率即可达到80%以上;AMC14AB的聚合速率方程为Rp=k[M]0.92[I]0.48,说明链终止为双基终止方式,引发过程与单体无关;聚合表观活化能为80.72kJ/mol。     

Preparation and Unimolecular-Micellization Behavior of Homopolymer of Surface-Active Monomer AMC14AB

(2-acrylamido) ethyl tetradecyl dimethylammonium bromide (AMC14AB) was polymerized in aqueous solution to form the homopolymer P(AMC14AB). The physicochemical properties of P(AMC14AB) in aqueous solution were mainly studied with fluorescent probe method, surface tension measurement and conductometry. The experimental results show that the aggregation morphology of P(AMC14AB) in aqueous solution is unimolecular micelle as expected. Being different from conventional multimolecular micelle systems, the unimolecular micelle system of P(AMC14AB) not only shows critical micellar concentration (CMC=0), (i.e.once added to pure water, the surface tension decreases immediately in spite how small the density is), but also the surface tension stays almost the same with the concentration increasing. That is to say, there is no mutational point on the relationship curve between surface tension and concentration. Furthermore, the unimolecular micelle system of P(AMC14AB) has no Krafft temperature, i.e. at any temperature, so long as it is dissolved in water, the unimolecular micelles will form. Besides this, for the solubilization of hydrophobic organic substances, the unimolecular micelle system of P(AMC14AB) is obviously different from the common multimolecular micelle system, having no turning point on the relationship curve between toluene solubilizaion amount and P(AMC14AB) concentration, and the solubilizing ability of the unimolecular-micelle system of P(AMC14AB) for hydrophobic organic substances is much higher than that of the conventional multimolecular micelle solutions of common surfactants, such as centyl trimethyl ammonium bromide.     

Electrolyte effect on mixed micelle and interfacial properties of binary mixtures of cationic and nonionic surfactants

In the present work, the adsorption behavior at the liquid-air interface and micellization characteristics of mixtures of cetyltrimethylammonium bromide (CTAB) and p-(1,1,3,3-tetramethylbutyl) polyoxyethylene (TritonX-100) in aqueous media containing different concentrations of NaBr were investigated by surface tension and potentiometry measurements. From plots of surface tension (gamma) as a function of solution composition and total surfactant concentration, we determined the critical micelle concentration (CMC), minimum surface tension at the CMC (gamma(CMC)), surface excess (Gamma(max)), and mean molecular surface area (A(min)). On the basis of regular solution theory, the compositions of the adsorbed film (Z) and micelles (X(M)) were estimated, and then the interaction parameters in the micelles (beta(M)) and in the adsorbed film phase (beta(sigma)) were calculated. For all mole fraction ratios, the results showed synergistically enhanced ability to form mixed micelles as well as surface tension reduction. Furthermore beta was calculated by considering nonrandom mixing and head group size effects. It was observed that, for both the planar air/aqueous interface and micellar systems, the nonideality decreased as the amount of electrolyte in the aqueous medium was increased. This was attributed to a decrease of the surface charge density caused by increasing the concentration of bromide ions.     

Solubilization and Interactions of Thiram with Surfactants: Micellar Effects on Adsorption Characteristics of Thiram onto Activated Carbon

The solubilization of thiram was studied in micellar solutions of two surfactants possessing the same hydrocarbon tail but different hydrophilic head groups, namely sodium dodecyl sulfate and dodecyltrimethylammonium bromide. Conductivity, spectrophotometry, and surface tension measurements have been used in quantitative analysis of the interaction between thiram and surfactants. In this work the adsorption of thiram onto selected two different activated carbons has been also studied in the absence and presence of micelles. The interaction of thiram in different micellar solutions provided information about the characteristics of adsorption properties of poorly soluble pesticide thiram onto activated carbon in the presence of micelles.     

Structure and properties of aqueous dispersions of sodium dodecyl sulfate with carbon nanotubes

The dispersing action of the surfactant (sodium dodecyl sulfate, SDS) on the carbon nanotubes (CNT) in aqueous medium has been studied. Electron microscopy, molecular docking, NMR and IR spectroscopies were applied to determine the physical-chemical properties of CNT dispersions in SDS—water solutions. It was established that micellar adsorption of the surfactant on the surface of carbon material and solubilization of SDS in aqueous medium contribute to improving CNT dispersing in water solutions. It was shown that the non-polar hydrocarbon radicals of a single surfactant molecule form the highest possible number of contacts with the graphene surface. Upon increase of the SDS in solution these radicals form micelles connected with the surface of the nanotubes. At the sufficiently high SDS concentration the nanotube surface becomes covered with an adsorbed layer of surfactant micelles. Water molecules and sodium cations are concentrated in spaces between micelles. The observed pattern of micellar adsorption is somewhat similar to a loose bilayer of surfactant molecules.     

The Self-Association and Mixed Micellization of an Anionic Surfactant,Sodium Dodecyl Sulfate,and a Cationic Surfactant,Cetyltrimethylammonium Bromide: Conductometric,Dye Solubilization,and Surface Tension Studies

In the present study, we investigate the self-association and mixed micellization of an anionic surfactant, sodium dodecyl sulfate (SDS), and a cationic surfactant, cetyltrimethylammonium bromide (CTAB). The critical micelle concentration (CMC) of SDS, CTAB, and mixed (SDS + CTAB) surfactants was measured by electrical conductivity, dye solubilization, and surface tension measurements. The surface properties (viz., C₂₀ (the surfactant concentration required to reduce the surface tension by 20 mN/m), Π_CMC (the surface pressure at the CMC), Γ_max (maximum surface excess concentration at the air/water interface), and A_min (the minimum area per surfactant molecule at the air/water interface)) of SDS, CTAB, and (SDS + CTAB) micellar/mixed micellar systems were evaluated. The thermodynamic parameters of the micellar (SDS and CTAB), and mixed micellar (SDS + CTAB) systems were evaluated.

A schematic representation of micelles and mixed micelles.     

SOLUBILIZATION SITES AND ACID-BASE FORMS OF DIBUCAINE-HYDROCHLORIDE IN NEUTRAL AND CHARGED MICELLAR SOLUTIONS

Steady-state and time-resolved emission spectroscopic techniques have been employed to characterize the drug species of dibucaine and to identify its location in micellar Triton X-100 (neutral), hexadecyltrimethyl ammonium bromide (cationic) and lithium dodecyl sulfate (anionic) solutions at 77 K. Under physiological conditions, the dibucaine is shown to exist in the free base form (D) while solubilized in the hydrocarbon core of neutral micelles. In cationic micellar solution, dibucaine exists as the monocation species (DH+) where the anesthetic is solubilized in the extramicellar aqueous solution and D is solubilized in the hydrophobic region with close proximity to the micellar interface. In the anionic micelles, interfacial solubilization is most consistent with a site in which the tertiary amino group of the monocation dibucaine (DH+) is anchored at the micellar interface with its quinoline analog penetrating the hydrophobic region. The distinct properties observed for the drug species (i.e. D and DH+) and their solubilization sites in micelles are consistent with a balance between hydrophobic forces, surface polarity and the interfacial electrostatic potential present in the micellar solubilization sites. These observations could lend insight into the molecular basis of pharmacological action, in particular the mechanism of local anesthetic drug transport across membranes.     

Electrochemical reduction of p-nitrosodiphenylamine in, a cationic micellar system

The electroreduction of p-nitrosodiphenylamine (p-NDPA) in an alkaline aqueous solution containing cetyltrimethylammonium bromide (CTAB) as a cationic surfactant was investigated by polarography, cyclic and rotating disc voltammetry. It was found that the reduction of p-NDPA in cationic micellar systems takes place by the ECE mechanism, and, compared to the reduction of the same compound in a homogeneous water solution, has a somewhat lower rate of the overall electrode reaction. The lower reaction rate of p-NDPA reduction in micellar medium is probably due to three main factors: solubilization of p-NDPA in CTAB micelles, adsorption of monomeric surfactant species at the electrode surface and a lower rate of the base catalyzed dehydration reaction (C-step) in the micellar system.     

Influence of sodium sulfate or sodium sulfite on the solubilization of benzylalcohol in cationic micellar solutions

The enthalpy of benzylalcohol (BzOH) solution has been determined as a function of alcohol concentration in aqueous trimethyltetradecylammonium bromide (TTAB) solutions in the presence of sodium sulfite or sodium sulfate up to high salt concentration. The electrolytes studied do not seem to induce TTAB sphere-torod transition at least up to 0.6 mol/kg of salt. Comparison with the enthalpic behavior of BzOH in sodium dodecylsulfate solutions and with that of 1-pentanol in both cationic and anionic micellar solutions suggests that the solubilization of BzOH in TTAB solutions is specifically favored by intramolecular interactions between alcohol molecules within the cationic micelles. The replacement of the bromide counterions by the sulfite or sulfate ions has been studied using potentiometry with an ionselective electrode in the case of trimethylhexadecylammonium bromide (CTAB). No difference could be detected between the effects of either divalent anions on the rate of change of the bromide ion-condensation with the salt/surfactant concentration ratioR. The degree of counter-ion condensation on micellar surface depends not only on theR values, but also on the total surfactant concentration.     

Micellar solutions of sulfobetaine surfactants in water-ethylene glycol mixtures: surface tension, fluorescence, spectroscopic, conductometric, and kinetic studies

Micellization in water-ethylene glycol (EG) N-dodecyl, N-tetradecyl, and N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (SB3-12, SB3-14, and SB3-16, respectively) micellar solutions, with the weight percent of EG changing within the range 0-40, was studied by means of surface tension measurements. Information about the influence of the added EG on the aggregation number of the sulfobetaine micelles and on the polarity of the interfacial region of micelles was obtained through fluorescence and spectroscopic measurements. Surface tension measurements also provide information about the dependence of the surface excess concentration, the minimum area per surfactant molecule, the surface pressure at the cmc, and the standard Gibbs energy of adsorption on the added weight percent of the organic solvent. The Gordon parameter of the water-EG mixtures was also estimated by means of surface tension measurements. The thermodynamic and structural changes originated by the presence of EG control the micellar kinetic effects observed in the reaction methyl 4-nitrobenzenesulfonate + Br(-) occurring in the water-EG sulfobetaine micellar solutions. Information about the distribution of bromide ions between the bulk and micellar pseudophases was obtained through conductivity measurements. The kinetic micellar effects were quantitatively explained by using the pseudophase kinetic model.