表面活性剂TX-100与SDBS胶束中光解苯甲醛自由基的化学诱导动态电子极化

利用时间分辨ESR波谱仪，研究了苯甲醛在乙二醇和表面活性剂SDBS，TX-100 的胶束溶液中的激光光解化学诱导动态电子极化（CIDEP）现象。苯甲醛在激光照 射下可以从体系和自身中得到氢生成α-羟基苄自由基和苯酰自由基，在SDBS胶束 中是自由基对机理RPM极化，而在TX-100胶束中是三重态机理TM极化。计算机模拟 谱图进一步证实了自由基的产生和极化机理。     

表面张力法和电导法对比测定表面活性剂临界胶束浓度*

通过比较表面张力法和电导法测定阴离子表面活性剂十二烷基硫酸钠(SDS)和非离子表面活性剂辛基酚聚氧乙烯醚(TX-100)的临界胶束浓度的实验效果,明确了2种方法的优劣。 采用挂环法测试了不同浓度SDS和TX-100水溶液的表面张力,得到了它们的临界胶束浓度以及饱和吸附量、分子截面积;采用电导法研究上述2种表面活性剂溶液的电导率曲线,仅得到SDS的临界胶束浓度。与电导法相比,表面张力法得到的表面活性剂性质信息更多,应用更广泛。该实验使学生加深理解不同电性表面活性剂临界胶束浓度的性质及测定方法,明确不同方法的优缺点,扩大知识面,同时也提高学生处理数据的能力,为学生今后进一步学习应用表面活性剂打下良好基础。     

吲哚方酸菁染料在表面活性剂水溶液中的光降解

考察了4种含有不同N位取代基的对称吲哚方酸菁染料在阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)、阴离子表面活性剂十二烷基硫酸钠(SDS)和非离子表面活性剂曲拉通(TX-100)水溶液中的光降解行为,结果表明,表面活性剂对染料分子具有保护作用,其影响大小为CTAB>TX-100>SDS,分子中有羧基的染料受影响程度最大。在表面活性剂浓度较低时,染料光降解程度随着表面活性剂浓度的增加而增加,但形成胶束后,染料的光降解程度则随着表面活性剂浓度的升高而降低。     

在金属-铬天青S铬合物可见光度法中表面活性剂-诱导变色的机理

——本文研究在Be~(2+)、Cu~(2+)和Al~(3+)的铬天青S(CAS)络合物可见光度法中,表面活性剂一诱导变色的机理。在阳离子表面活性剂(溴化十六烷基三甲铵、CTAB)存在下,对所有三种金属络合物,均观察到摩尔吸光系数的增加和最大吸收波长的红移。在非离子表面活性剂(TritonX-100,即TX-100)存在下,对Be~(2+)及Cu~(2+)的络合物,也观察到相同情况。在高离子强度时,发现阴离子表面活性剂(十二烷基硫酸钠,SDS)有类似的效应。在使用TX-100和SDS时,只涉及到严格意义下的胶束相互作用。而在使用CTAB时,既观察到包括表面活性剂单体在內的三元络合物的形成,也观察到了胶束相互作用,即在低浓度CTAB时,形成具有明确组成的络合物;到临界胶束浓度以上时,则为胶束相互作用。所有“表面活性剂增敏”体系的光谱都很类似,意味着生色团在三元络合物中和在胶束中有类似的微环境。     

表面活性剂胶束形状随浓度转变的核磁共振研究

运用核磁共振一维氢谱和自扩散实验方法研究了聚乙烯乙二醇异辛酚醚(TX-100)、十二烷基苯磺酸钠(SDBS)和十四烷基三甲基溴化铵(TTAB)三种不同类型的表面活性剂在重水溶液中的胶束形状转变, 发现它们在临界胶束浓度以上的各自相应浓度都有胶束形状的变化(由球状转变为椭球状或棒状). 在常温常压和没有其他添加剂的情况下, 表面活性剂溶液浓度高于其临界胶束浓度时, 球状胶束开始形成. 核磁共振一维氢谱和自扩散实验的结果显示, 当溶液浓度继续增加到一定程度时, 溶液中表面活性剂分子的化学位移和自扩散系数的变化速率都有明显的转折, 这说明溶液中球状胶束开始发生转变. 进一步通过仔细分析对比核磁共振一维氢谱中各基团谱峰, 发现表面活性剂胶束亲水表面上的质子的化学位移变化速率要远高于其疏水内核中的质子, 据此推测胶束形状很可能由球状转变为椭球状或棒状.     

盐引发阴离子/非离子表面活性剂复配体系中囊泡自发形成

在无盐时, 阴离子表面活性剂十二烷基苯磺酸钠(SDBS)与非离子表面活性剂壬基酚聚氧乙烯(10)醚(TX-100)的复配体系中只有混合胶束存在, 而盐的加入即可以引发体系中囊泡的自发形成, 这使得囊泡的形成变得更加简单. 引发机理可以归因于盐对离子表面活性剂的极性头双电层的压缩作用, 减少了极性头的面积, 加上非离子表面活性剂的参与使得堆积参数P增加, 导致了半径更大的聚集体的形成. 制作了SDBS/TX-100/盐水拟三元相图, 通过目测和表面张力的变化确定了囊泡形成的带状区域, 并用负染色电镜(TEM)对囊泡进行了表征, 同时测定了盐度以及相同盐度下表面活性剂浓度对囊泡粒径的影响, 发现囊泡的粒径随着盐度的增加而增加, 而在同一盐度下, 囊泡的粒径基本不受表面活性剂浓度的影响.     

核磁共振法研究三苯甲烷类酸性染料与非离子表面活性剂的相互作用

研究显色螯合剂和表面活性剂之间的相互作用,对于探讨胶束增溶分光光度法的反应机理是很重要的。等曾用核磁共振和分光光度两种方法研究了非离子表面活性剂OS-20与铬天青S(记作CAS)和磺酸铬青的相互作用,并对作用机理提出了他们的看法。本文用NMR研究了非离子表面活性剂TX-100和乳化剂OP与CAS和漂蓝6B(记作ECAB)的相互     

胶束微环境下光解苯半醌负离子基的CIDEP研究

用高时间分辨电子自旋共振(TRESR)波谱仪, 研究对苯醌(PBQ)在不同的介质中光解苯半醌自由基的化学诱导动态电子自旋极化(CIDEP)。实验结果指出, 在乙二醇溶液中得到苯半醌自由基(PBQH)和以碳为中心的自由基R(OH)2。在乙二醇/水溶液中, 得到以PBQH的六条峰为主的谱线图, 然后在该体系中随着加入表面活性剂TX-100, AOT的浓度增加, 苯半醌负离子基(PBQ^-)的谱线强度增加, 而PBQH的谱线减弱直至消失。本文从自由基所处微环境性质出发, 讨论其极化传递机理和有关物理化学性质。     

高分子表面活性剂的合成

介绍了高分子表面活性剂的合成方法及其不同于低分子表面活性剂的特点,重点从离子聚合、活性自由基聚合、缩合聚合、开环聚合、高分子化学反应、自由基胶束聚合等角度综述了近几-来高分子表面活性剂的合成研究进展.     

混合阴阳离子表面活性剂体系的物理化学性质

测定并比较了TX-100(C_8ΦE_(9.8))及TX-100的硫酸盐(_8CΦE_(9.8)S)分别与阳离子表面活性剂(C_nPy, n=10, 12, 14; C_mNM_3, m=16, 18)混合后, 混合表面活性剂的表面活性、水溶液的稳定性、起泡能力和泡沫稳定性等物理化学性质。     

蒽醌在乙二醇/Triton X胶束与乙二醇/三乙胺溶液中光还原的时间分辨电子自旋共振研究

用时间分辨电子自旋共振研究了乙二醇/Triton X 胶束与乙二醇/三乙胺溶液中蒽醌(AQ)的光还原. 在蒽醌/乙二醇/Triton X/H₂O胶束中, 获得蒽半醌自由基AQH^•的很强的TR-ESR信号, 并检测到一定强度的负离子基AQ^•－ TR-ESR信号. 在蒽醌/乙二醇/三乙胺/H₂O体系中同时有较强的AQH^•与AQ^•－的TR-ESR信号. 分析并讨论了蒽醌在两种体系中的还原过程. 根据CIDEP的强度与Triton X及三乙胺浓度的关系, 推求了三线态³AQ^*对自由基AQH^•的反应速率常数. 根据化学诱导动态电子极化(CIDEP)信号随时间的变化, 计算了AQH^•的CIDEP弛豫时间.     

The properties of a binary mixture of nonionic surfactants in water at the water/air interface

The behavior of mixed nonionic/nonionic surfactant solutions, that is, p-(1,1,3,3-tetramethylbutyl)phenoxy poly(ethylene glycol)s Triton X-100 (TX100) and Triton X-165 (TX165) have been studied by surface tension and density measurements. The obtained results of the surface tension measurements were compared with those calculated from the relations derived by Joos, Miller, and co-workers. From the comparison, it appeared that by using these two approaches the adsorption behavior of TX100 and TX165 mixtures at different mole fractions can be predicted. The negative deviation from the linear relationship between the surface tension and composition of TX100 and TX165 mixtures in the concentration range corresponding to that of the saturated monolayer at the interface, the values of the parameters of molecular interaction, the activity coefficients, as well as the excess Gibbs energy of mixed monolayer formation calculated on the basis of Rosen and Motomura approaches proved that there is synergism in the reduction of the surface tension of aqueous solutions of TX100 and TX165 mixture when saturation of the monolayer is achieved. The negative parameters of intermolecular interaction in the mixed micelle and calculations based on MT theory of Blankschtein indicate that there is also synergism in the micelle formation for TX100 and TX165 mixture. It was also found that the values of the standard Gibbs energy of adsorption and micellization for the mixture of these two surfactants, which confirm the synergetic effect, can be predicted on the basis of the proposed equations, which include the values of the mole fraction of surfactant and excess Gibbs energy TX100 and TX165 in the monolayer and micelle.     

Triton X-100/CTAB在乙二醇/水混合溶剂中的热力学性质和胶团化行为

利用表面张力法, 研究了非离子表面活性剂Triton X-100和离子表面活性剂十六烷基三甲基溴化铵(CTAB)混合体系在混合极性溶剂乙二醇/水(乙二醇的体积分数分别为5%、10%和20%)中的热力学性质和胶团化行为. 结果表明, 混合体系在乙二醇水溶液中存在协同效应, 临界胶束浓度随乙二醇含量的增加而增大. 利用Rubingh和Maeda模型计算了混合物中各组分在胶团相中的组成、相互作用参数以及自由能的贡献. 在实验研究的乙二醇浓度范围内, 发现该非离子/离子混合体系在离子组分摩尔分数约为0.3时, 协同效应最强.     

Time-resolved measurements of the photolysis and recombination of adenosylcobalamin bound to glutamate mutase

Femtosecond to nanosecond transient absorption spectroscopy is used to investigate the photolysis of 5'-deoxyadenosylcobalamin (coenzyme B12, AdoCbl) bound to glutamate mutase. The photochemistry of AdoCbl is found to be inherently dependent upon the environment of the cofactor. Excitation of AdoCbl bound to glutamate mutase results in formation of a metal-to-ligand charge transfer intermediate state which decays to form cob(II)alamin with a time constant of 105 ps. This observation is in contrast to earlier measurements in water where the photohomolysis proceeds through an intermediate state in which the axial dimethylbenzimidazole ligand appears to have dissociated, and measurements in ethylene glycol where prompt bond homolysis is observed (Yoder, L. M.; Cole, A. G.; Walker, L. A., II; Sension, R. J. J. Phys. Chem. B 2001, 105, 12180-12188). The quantum yield for formation of stable radical pairs in the enzyme is found to be phi = 0.05 +/- 0.03, and the resulting intrinsic rate constants for geminate recombination and "cage escape" are 1.0 +/- 0.1 and 0.05 +/- 0.03 ns(-1), respectively. The rate constant for geminate recombination is 30% less than that observed for AdoCbl in water or ethylene glycol. This reduction is insufficient to account for the 10(12)-fold increase in the homolysis rate observed when substrate is bound to the protein. Finally, the protein provides a cage to prevent diffusive loss of the adenosyl radical; however, the ultimate yield for long-lived radicals is determined by the evolution from a singlet to a triplet radical pair as proposed for AdoCbl in ethylene glycol.     

Wettability of a glass surface in the presence of two nonionic surfactant mixtures

Measurements of the advancing contact angle (theta) were carried out for aqueous solution of p-(1,1,3,3-tetramethylbutyl)phenoxypoly(ethylene glycol), Triton X-100 (TX100), and Triton X-165 (TX165) mixtures on glass. The obtained results indicate that the wettability of glass depends on the concentration and composition of the surfactant mixture. The relationship between the contact angle and concentration suggests that the lowest wettability corresponds to the concentration of TX100 and TX165 and their mixture near the critical micelle concentration (CMC). The minimum of the dependence between the contact angle and composition of the mixtures for each concentration at a monomer mole fraction of TX100, alpha, equals 0.2 and 0.4 points to synergism in the wettability of the glass surface. In contrast to the results of Zisman ( Zisman, W. A. In Contact Angle, Wettability and Adhesion; Gould, R. F., Ed.; Advances in Chemistry Series 43; American Chemical Society Washington, DC, 1964; p 1 ) there was no linear dependence between cos theta and the surface tension of aqueous solutions of TX100 and TX165 mixtures for all studied systems, but a linear dependence exists between the adhesional tension and surface tension for glass, practically, in the whole concentration range of surfactants studied, the slopes of which are positive in the range of 0.43-0.67. These positive slopes indicate that the interactions between the water molecules and glass surface might be stronger than those between the surface and surfactant molecules. So, the surface excess of surfactant concentration at the glass-water interface is probably negative, and the possibility for surfactant to adsorb at the glass/water film-water interface is higher than that at the glass-water interface. This conclusion is confirmed by the values of the work of adhesion of "pure" surfactants, aqueous solutions of surfactants, and aqueous solutions of their mixtures to the glass surface and by the negative values of glass-water interfacial tension determined from the Young equation in the range of surfactant concentrations corresponding to their unsaturated monolayer at the water-air interface.     

Supramolecular complex of [60]fullerene-grafted polyelectrolyte and surfactant: mechanism and nanostructures

Water-soluble, pH-responsive mono- and di-[60]fullerene end-capped poly(acrylic acid)s (PAA-C60 and C60-PAA-C60) were synthesized using the atom transfer radical polymerization technique. Isothermal titration calorimetry, dynamic light scattering, UV-vis spectroscopy, and transmission electron microscopy were employed to study the supramolecular complexation between fullerene end-capped PAAs and nonionic surfactant, polyethylene glycol (9-10) tert-octylphenyl ether, also known as Triton X100 (TX100) at different pH values. At pH < 4, TX100 bound specifically to C60 domains driven by hydrophobic and pi-pi interactions between TX100 and fullerene molecules. The binding was exothermic, and the magnitude of the interaction decreased gradually with increasing pH. The amount of polymer-bound TX100 was proportional to the fullerene content, which was approximately 1.3 and approximately 2.5 mM for 5 mM (concentration of carboxylic groups) PAA-C60 and C60-PAA-C60, respectively. Morphological transformations resulting in the formation of polymer/surfactant complex (PSC) precipitates in the course of binding were observed for both polymers. The PSC of PAA-C60 possessed a dense spherical structure, whereas the PSC of C60-PAA-C60 possessed a lamellar stacking structure. The PSC precipitates resolubilized in excess amounts of TX100 to form stable aggregates.     

非离子表面活性剂的吸附机理和表面胶团化对二氧化硅悬浮液稳定性的影响

测定了CAB-O-SIL在290.7K和304.2K时自水和1mol/LNaCl溶液中吸附非离子表面活性剂TritonX-100(TX100)的吸附等温线。结果表明,吸附量随温度升高而增加。NaCl的存在也使吸附量增加。运用生成表面胶团的吸附理论处理了实验结果,求得了表面胶团化的平衡常数、表面胶团的平均聚集数、临界表面胶团浓度和表面胶团化的标准热力学函数。实验表明,随TX100浓度的增大,CAB-O-SIL悬浮液稳定性出现不规则的变化。加入NaCl的效应是使悬浮液的稳定性下降和促进表面胶团的形成。结合吸附研究结果,提出了一个涉及表面胶团的颗粒相互作用模型,合理地解释了悬浮液稳定性的实验结果。     

Effect of ethylene glycol on the thermodynamic and micellar properties of Tween 20

The aggregation behaviour of Tween 20 in ethylene glycol-water mixed solvents has been investigated using surface tension, density, static and dynamic light scattering, and fluorescence measurements. Micellar and surface thermodynamics data were obtained from the temperature dependence of critical micelle concentrations in various aqueous mixtures of ethylene glycol. In order to evaluate the influence of the cosolvent, the differences in the Gibbs energies of micellization of Tween 20 between water and binary solvents were determined. This study allowed us to conclude that the ability of ethylene glycol to act as a structure breaker and its interaction with the surfactant hydrophilic group are the controlling factors of the micellization process. From the evaluation of the thermodynamics of adsorption at the solution-air interface, it was determined that the surface activity of the surfactant decreases slightly with increasing concentration of ethylene glycol at a given temperature. Partial specific volume data, obtained by density measurements, indicate that the fraction of solvent molecules interacting with the micelle, via hydrogen bonds, remained roughly constant. The effect of cosolvent on the size and solvation of the aggregates was analysed by means of static and dynamic light scattering measurements. It was found that the aggregation number decreased, whereas the whole micellar solvation increased with the ethylene glycol content. Micellar micropolarity was examined using two different probes, pyrene and 8-anilinonaphthelene-1-sulfonic acid, and was found to increase with ethylene glycol addition, accompanied by an enhanced solvation. Fluorescence polarization measurements found by using coumarin 6 as a hydrophobic probe revealed an increase in the micellar microviscosity. The observed trends in these microenvironmental properties were ascribed to a participation by ethylene glycol in the micellar solvation layer.     

Dark and photoinduced interactions between Trolox, a polar-solvent-soluble model for vitamin E, and riboflavin

The aerobic riboflavin (Rf)-sensitized visible-light irradiation of Trolox (TX), a polar-solvent-soluble model for vitamin E, has been studied employing stationary photolysis, polarographic detection of oxygen uptake, stationary and time-resolved fluorescence spectroscopy, and laser flash photolysis. Results indicate that in methanolic solution, no dark complexation exists between Rf and TX. The latter quenches singlet and triplet states of Rf, with rate constants of 6.2 x 10(9) M(-1) s(-1) and 4.7 x 10(9) M(-1) s(-1), respectively. The photodecomposition of Rf, a known process taking place from triplet Rf, has been found to depend on the concentration of dissolved TX: at >/=30 mM very slight Rf photodecomposition occurs due to the massive quenching of excited singlet Rf, while at TX concentrations < or =1 mM triplet Rf is photogenerated and subsequently quenched either by oxygen, giving rise to O(2)((1)Delta(g)), or by TX, yielding semireduced Rf through an electron transfer process. Complementary experiments performed in pure water employing superoxide dismutase and sodium azide inhibition of the oxygen uptake, in coincidence with flash photolysis data, indicate that superoxide anion and singlet molecular oxygen are generated, likely by the reaction of the anion radical from Rf with dissolved oxygen, also yielding neutral, ground state Rf or by energy transfer from triplet Rf to ground-state oxygen, respectively. The final result is that both TX and Rf are photodegraded, likely through oxidation with activated oxygen species. In the absence of oxygen no degradation of TX can be detected, but Rf photodegradation is favoured because Rf regeneration is avoided.