氧杂氟表面活性剂及其与同电性碳氢表面活性剂混合溶液的表面吸附和胶团形成

研究了四种氧杂氟表面活性剂及其与同电性直链碳氢表面活性剂混合体系的表面活性;考察了混合体系中的表面吸附和胶团形成现象.在吸附层中分子间有明显的互疏作用,在溶液中倾向于各自形成胶团.还讨论了反离子结合度不同对理想混合胶团的组成及cmc的计算的影响,提出了一般的计算式.实验测得这些氧杂氟表面活性剂有较低的胶团反离子结合度.     

表面胶团修饰电极电化学测定双酚A的增敏机理及抗污性能研究

分别以2种阴离子表面活性剂(SDS、SDBS)、3种季铵盐阳离子表面活性剂(CTAB、TTAB、DTAB)和2种季铵盐型双子表面活性剂(12-3-12、12-4-12)修饰碳糊电极。通过原子力显微镜、接触角以及分析物在电极表面的电化学行为探讨了不同表面活性剂在电极表面的吸附情况,推测在浓度大于临界胶束浓度(CMC)时,季铵盐型阳离子表面活性剂CTAB、TTAB、12-3-12和12-4-12在碳糊电极表面形成了圆柱形的表面胶团,而DTAB和SDS可能是饱和单分子层吸附。以BPA为分析物,研究了表面活性剂修饰电极对BPA的电化学增敏机理,结果表明修饰电极对双酚A(BPA)的电化学增敏作用主要是因为表面胶团对BPA的增溶作用,表面活性剂和BPA间的阳离子-π作用是表面胶团增溶BPA的主要原因。     

氧杂氟表面活性剂及其与同电性碳氢表面活性剂混合溶液的表面吸附和胶团形成

研究了四种氧杂氟表面活性及其与同电性直链碳氢表面活性剂混合体系的表面活性;考察了混合体系中的表面吸附和胶团形成现象.在吸附层中分子间有明显的互疏作用,在溶液中倾向于各自形成胶团.还讨论了反离子结合度不同对理想混合胶团的组成CMC的计算的影响,提出了一般的计算式,实验测得这些氧杂氟表面活性剂有较低的胶团反离子结合度.     

荧光探针法研究双子型阳离子表面活性剂与明胶的相互作用

利用荧光探针法研究了双子型阳离子表面活性剂与明胶的相互作用,考察了此类表面活性剂的分子结构和明胶对临界胶团浓度(cmc)、胶团聚集数(N_agg)和胶团微极性的影响.结果表明,当双子型阳离子表面活性剂的疏水基增长时,cmc减少,N_agg增加,胶团的微极性降低;加入明胶后,双子型阳离子表面活性剂的N_agg减少,cmc和胶团微极性增加.     

全氟辛酸与十二烷基硫酸钠混合溶液中的胶团形成

用表面张力法、电导法,pH测定法研究全氟辛酸-十二烷基硫酸钠混合水溶液的胶团形成及全氟辛酸胶团的特性.结果表明:(1)电导法与pH测定法弥补了表面张力法的不足,进一步证明在碳氟链表面活性剂与碳氢链表面活性剂混合水溶液中形成两种胶团.(2)全氟辛酸与十二烷基硫酸钠混合水溶液中所形成的两种胶团,分别基本上由全氟辛酸和十二烷基硫酸钠组成.十二烷基硫酸钠的存在对全氟辛酸胶团的形成不显示影响.全氟辛酸的氢离子对十二烷基硫酸钠胶团显示反离子效应.(3)全氟辛酸是典型的离子型表面活性剂,由于它对氢离子的结合力特别强,其胶团几乎是电中性的.这一特性可以解释全氟辛酸-十二皖基硫酸钠混合溶液胶团形成的机制.     

低碳醇对季铵盐二聚表面活性剂C_(12)-2-C_(12)·2Br胶团化行为的影响

随着丙、丁、戊、已醇的加入，与季铵盐二聚表面活性剂C_(12)-2-C_(12)· 2Br组成了混合胶团，醇分子以烷烃链插入胶团中，羟基则位于胶团栅栏层处。这 减弱了表面活性剂离子头基间的静电排斥力，使临界胶团浓度(cmc)降低，同时使 胶团表面反离子解离度增大。随着醇分子的烷烃链增长，这种影响更为显著。     

卵清蛋白与离子型表面活性剂的相互作用

本文通过荧光光谱法、紫外-可见吸收光谱法和透射电镜并结合电导率测定分别研究了水中卵清蛋白与阴离子表面活性剂十二烷基硫酸钠（SDS）和阳离子表面活性剂十二烷基三甲基溴化铵（DTAB）和十六烷基三甲基溴化铵（CTAB）之间的相互作用。研究结果表明卵清蛋白可以增加SDS和CTAB的临界胶束浓度,但对DTAB的临界胶束浓度没有影响。阴离子表面活性剂可以使卵清蛋白构象完全伸展,而阳离子表面活性剂却不具备此种作用。表面活性剂单体与卵清蛋白的相互作用强于表面活性剂胶束与卵清蛋白的相互作用。     

酰胺基团对Gemini表面活性剂表面活性和聚集行为的影响

本文合成了含酰胺基团和不含酰胺基团的两类Gemini阳离子表面活性剂,测定了其表面活性参数,研究了酰胺基团对表面活性剂的表面活性和聚集行为的影响。结果表明,酰胺基团提高了Gemini阳离子表面活性剂的临界胶团浓度,降低了胶团聚集数,增强了胶团微极性,增大了表面活性剂的饱和吸附量。     

离子液体型表面活性剂C12mimBr与普通表面活性剂混合性质的研究

研究了离子液体型表面活性剂C12mimBr与阳离子表面活性剂Gemini 12-3-12, DTAB及阴离子表面活性剂SDS复配体系的性质, 并分别采用Rubingh-Margules模型和Rubingh-正规溶液模型计算了临界胶束浓度和混合胶团组成. 研究发现, 两表面活性剂分子结构的匹配性及带电头基之间的相互作用是影响混合溶液性质的主要因素. 对于分子结构差别较大的C12mimBr与Gemini 12-3-12的混合, 其行为远远偏离理想混合性质; 对疏水链长相同仅亲水头基不同的C12mimBr与DTAB则接近于理想混合; 而对C12mimBr＋SDS的复配体系, 正、负电荷间强烈的相互吸引使得混合体系大大偏离理想行为. 计算发现, 两种理论模型得到的混合胶团组成基本一致, 但Rubingh-Margules模型预测的临界胶束浓度比Rubingh-正规溶液模型要好     

碳氟醇对阳离子表面活性及胶团反离子结合度的影响

用表面张力及电动势法研究了Ｃ１０Ｈ２１Ｎ（ＣＨ３）３Ｂｒ，Ｃ１２Ｈ２５Ｎ（ＣＨ３）３Ｂｒ和Ｃ３Ｆ７ＣＨ２ＯＨ混合水溶液的表面与胶团性质。结果表明，对于阳离子表面活性剂，Ｃ３Ｆ７ＣＨ２ＯＨ的加入一方面增加表面活性，另一方面降低胶团反离子结合度。后者不同于阴离子表面活性剂／Ｃ３Ｆ７ＣＨ２ＯＨ混合体系，可归因于Ｃ３Ｆ７ＣＨ２ＯＨ略有酸性，因而具备一些类似阴离子表面活性剂的性质。     

Competition between Monovalent and Divalent Counterions in Surfactant Systems

Competition between mono- and divalent ions in the association of counterions to the headgroups of amphiphiles was studied in one surfactant system with organic counterions (piperidine⁺/piperazine²⁺octanesulfonate) and one with inorganic counterions (Na⁺/Ca²⁺octyl sulfate). By conductivity and¹³C NMR chemical shift measurements the critical micelle concentration (CMC) was found to decrease drastically when small amounts of divalent counterions were present in the system. Self-diffusion coefficients of surfactant ions and organic counterions were measured in the micellar phase by the Fourier transform pulsed-gradient spin-echo (FT-PGSE) NMR method. The degree of counterion binding in the micellar system with piperidine⁺/piperazine²⁺counterions was obtained from FT-PGSE NMR measurements. It was observed that the divalent counterions were more strongly bound than the monovalent counterions. The experimental results were compared with theoretical Poisson–Boltzmann calculations. The cell model was used to study the electrostatic effects. Good agreement between electrostatic theory and experiment was observed; however, an attractive force exists between the monovalent piperidine counterions and the micelle, probably because of hydrophobic interactions.     

Study of reverse micelles of di-isobutyl-phenoxy-ethoxy-ethyl-dimethyl-benzyl ammonium methacrylate in benzene by nuclear magnetic resonance spectroscopy

(1)H NMR spectroscopy was used to investigate the aggregation of the surfactant di-isobutyl-phenoxy-ethoxy-ethyl-dimethyl-benzyl ammonium methacrylate (Hyamine-M) in benzene. Adding water makes swollen reverse micelles (microemulsion droplets). The droplets also contain cadmium ions and the sodium salt of the methacrylic acid. The critical micelle concentration of Hyamine-M was determined by NMR to be 3.95 mM under the current conditions. Two-dimensional NMR NOESY spectra were used to study the conformation of the surfactant in the micelle and the spatial localization of water and counterions. We found that the surfactant molecules are folded with both phenyl fragments oriented toward the micelle exterior and the oxyethylene and NCH(3) groups in the micelle core. The water molecules and counterions are distributed around the surfactant polar groups in the micelle interior and penetrate up to both aromatic rings. The investigated system can be further utilized as a microemulsion matrix for the synthesis of cadmium-containing semiconductor nanocrystals, eventually capped with a polymer shell, or of polymer nanoparticles.     

Presence or absence of counterion specificity in the interaction of alkylammonium surfactants with alkylacrylamide gels

Patterns in the interaction of cationic surfactants with nonionic polymer gels, which were inferred from a recent study from our laboratory, are confirmed by measurements of a series of alkylammonium surfactants with different counterions with a series of alkyl acrylamide gels of increasing hydrophobicity. Two swelling patterns were observed: Either the swelling continued above the surfactant critical micelle concentration (cmc) and the maximum swelling differed for different counterions and increased in the order of Br-相似文献   

Cation-π Interaction between the Aromatic Organic Counterion and DTAB Micelle in Mixed Solvents

The cation-π interaction between the aromatic organic counterion potassium hydrogen phthalate (KHP) and DTAB micelle in aqueous mixture of EG was investigated, using the techniques of conductivity measurements, UV absorption spectrum and NMR spectrum. The conductivity and UV spectrum studies were with respect to the effect of KHP on DTAB and that of DTAB micelle on KHP, respectively. According to the chemical shift changes of the aromatic ring and the surfactant methylene protons, it can be assumed that KHP penetrated into DTAB micelle with its carboxylic group protruding out of the micellar surface. And the strength of the interaction became weaker with the content of EG in the mixed solvent increasing.     

Aggregation and adsorption of sodium dioctylsulfosuccinate in aqueous ammonium chloride solution: role of mixed counterions

The critical micelle concentration (cmc) of sodium dioctylsulfosuccinate (AOT) was determined at 25 °C from surface tension and fluorescence methods in aqueous NH(4)Cl solution for assessing the influence of mixed counterions on the special counterion binding behavior (SCB) of AOT. The SCB of AOT refers to a sudden twofold increase in the value of the counterion binding constant (β) in aqueous medium when the concentration (c(*)) of the added 1:1 sodium salt is about 0.015 mol kg(-1), and it has been tested so far for sodium ion only. In the presence of sodium and ammonium mixed counterions also the SCB of AOT exist, but with lower c(*) (0.009 mol kg(-1) NH(4)Cl). Synergism in the cmc occurs due to mixed counterions. In the case of inorganic counterions, unlike the case with organic counterions, the cmc is dependent on the total counterion concentration in solution and negligibly on the specific type of counterion. Na(+) and NH(4)(+) bind almost equally to the micelle in the region of low β (below c(*)), but in the region of high β (above c(*)) NH(4)(+) binds predominantly. It has been shown that the theoretical expression for the surface excess of ionic surfactant+electrolyte system containing a single counterion can also be used to evaluate the surface excess in the presence of mixed counterions if the two counterions are considered to undergo Henry-type adsorption at the air-solution interface.     

Varying the counterions at a charged interface

The influence of different counterions on the adsorption behavior of the ionic soluble surfactant dodecyl-dimethylammonium-pyridimium bromide is investigated. The addition of potassium halogenides to aqueous solutions of the surfactant modifies the surface activity of the amphiphile and has a profound influence on the surface tension isotherms. The measured critical micelle concentration follows the order of the periodic table of elements which is in strong contrast to the surface excess. The number density of the adsorbed surfactants at the cmc does not depend on the amount of counterions in the solution but on the nature of the counterion. Furthermore, evidence is provided that the surface region is depleted on fluoride ions. Surface second harmonic generation and ellipsometry have been used to gain direct structural information which complement the thermodynamic considerations. The combination of both optical techniques yields the number density of the condensed counterions within the compact layer. A strategy to retrieve selected parameters of the ion binding model of Radke et al. is presented. The analysis of the optical data reveal the existence of a phase transition towards a surface condensed state with increasing salt condensation.     

Adsorption of aromatic counterions at the surfactant/water interface: a neutron reflectivity study of hydroxybenzoate and chlorobenzoate counterions at the hexadecyl trimethylammonium surfactant/water interface

Specular neutron reflectivity has been used to investigate the adsorption of the aromatic counterions hydroxybenzoate and chlorobenzoate at the hexadecyl trimethylammonium bromide surfactant monolayer/water interface. The degree of counterion binding and the location of the counterions at the interface are shown to depend on the isomeric form of the counterion. For hydroxybenzoate, the para-substituted counterion is located within the headgroup region of the surfactant monolayer, and there is of order one counterion for every two surfactant ions. For the ortho-substituted counterion, the degree of counterion binding is higher. There is of order 0.85 counterions for each surfactant ion, and the counterion is located within the hydrophobic region of the monolayer, some 5 A from the center of the headgroup distribution. Similar results were found for the chlorobenzoate counterion, but in that case it was the para-substituted counterion that was more tightly bound and located within the hydrophobic region of the surfactant monolayer. The results for the ortho-substituted hydroxybenzoate and for the para-substituted chlorobenzoate are consistent with those previously reported for the para-tosylate. The results are discussed in the context of the ability of the specific aromatic counterion isomer to promote massive micellar growth, and the results shed light on that mechanism.     

Spontaneous Stepwise Self‐Assembly of a Polyoxometalate–Organic Hybrid into Catalytically Active One‐Dimensional Anisotropic Structures

An inorganic–organic hybrid surfactant with a hexavanadate cluster as the polar head group was designed and observed to assemble into micelle structures, which further spontaneously coagulate into a 1D anisotropic structure in aqueous solutions. Such a hierarchical self‐assembly process is driven by the cooperation of varied noncovalent interactions, including hydrophobic, electrostatic, and hydrogen‐bonding interactions. The hydrophobic interaction drives the quick formation of the micelle structure; electrostatic interactions involving counterions leads to the further coagulation of the micelles into larger assemblies. This process is similar to the crystallization process, but the specific counterions and the directional hydrogen bonding lead to the 1D growth of the final assemblies. Since most of the hexavanadates are exposed to the surface, the 1D assembly with nanoscale thickness is a highly efficient heterogeneous catalyst for the oxidation of organic sulfides with appreciable recyclability.