季铵盐型双子表面活性剂16-4-16聚集状态的NMR研究

核磁共振弛豫，自扩散以及2D NOESY谱研究结果表明：双子表面活性剂16-4-16溶液在形成胶束的过程中，联结基团及其邻近的碳氢链质子形成胶束的壳层，而距离离子头较远的疏水质子位于胶束的内部. 与对应的单链的表面活性剂CTAB相比，其分子运动更受限制. 2D NOESY谱显示联接基团及临近的碳氢链的质子间有较强的交叉峰，表明形成胶束时，分子在联结基团附近堆积的较为紧密. 由2D NOESY谱计算得到的质子间距与HYPERCHEM模拟值有偏差，表明这些强交叉峰是分子间相互作用的结果，并且对应质子对在双子表面活性剂16-4-16分子中位于邻近的区域. 因此我们推测，双子表面活性剂16-4-16分子在球形胶束中形成特殊的排列方式.     

十八胺单分子膜的研究

通过测定在纯水和CdCl2 溶液亚相上十八胺单分子膜的平衡、循环π～A等温线及其动态弹性 ,发现在亚相中加入Cd2 + 可以使膜的液态相凝聚性增强 ,固态相凝聚性减弱 .液态的单分子膜在两种亚相上有较好的可回复性 ,而在固态膜中则不然 .这可归因于在水面上十八胺分子间可形成氢键 ,而在CdCl2 水溶液亚相上的十八胺则与Cd2 + 发生配位 ,形成了多配位络合物 ,两种情况下十八胺分子在高膜压区都会发生稳定的聚集 .静、动态弹性的比较表明 ,膜障的振动不利于十八胺分子与Cd2 + 间的配位作用     

NMR方法监测季铵型双子表面活性剂的胶束交换动力学（英文）

本文应用DNMR的方法测量了双子表面活性剂12-s-12和14-s-14(s=2, 3, 4)单体在溶液和胶束间的分子交换动力学参数,根据DNMR理论的简化公式,变温条件下测量了表面活性剂分子的逸出速率常数(k~-),根据阿伦尼乌斯公式拟合得到了逸出活化能(E_a~-).结果显示14-s-14和12-s-12的逸出速率常数分别在10~1和10~3 s~(-1)数量级,逸出活化能分别为54.04～73.64 kJ/mol和33.42～47.09 kJ/mol.随着联结基团长度的增大,14-s-14和12-s-12的逸出速率常数增大,逸出活化能减小.结合荧光探针实验测量微极性的结果,揭示了双子表面活性剂分子从胶束中逸出时经历了构象变化,支持了双子表面活性剂的两步分子交换机制.     

表面弹性对含可溶性活性剂垂直液膜排液的影响

针对含可溶性活性剂的垂直液膜排液过程,在考虑表面弹性作用的基础上,采用润滑理论建立了液膜厚度、表面速度、表面和内部活性剂浓度的演化方程组,通过数值计算分析了表面弹性和活性剂溶解度耦合作用下的液膜演化特征.结果表明：表面弹性是影响可溶性活性剂垂直液膜排液过程中必不可少的因素.排液初期,随表面弹性增加,液膜初始厚度增大,表面更趋于刚性化.随排液进行,弹性不同的液膜呈现不同的典型排液特征：当弹性较小时,液膜上部表面张力高,下部表面张力低,产生正向的马兰戈尼效应,与重力作用相抗衡.当弹性较大时,膜上部表面张力低,下部表面张力高,产生逆向的马兰戈尼效应,促使液膜排液加速,更易发生失稳.活性剂溶解度通过控制液膜表面的活性剂分子吸附量,进而影响表面弹性：当活性剂溶解度较大时,液膜厚度较小,很快发生破断;随溶解度降低,液膜稳定性增加,初始表面弹性也随之增大,并随液膜变薄逐渐接近极限膨胀弹性值.     

动态光散射研究胆固醇对DTAB/SDS阴阳离子液胞稳定性的影响

本文利用阴离子型界面活性剂十二烷基硫酸钠(SDS)和阳离子型界面活性剂十二烷基三甲基溴化铵(DTAB)形成DTAB/SDS离子对双亲分子,通过制膜、超声振荡与挤压等程序制备出阴阳离子液胞,并利用动态光散射技术探讨不同比例的胆固醇添加对液胞稳定性的影响。研究结果表明,添加胆固醇可以明显增强DTAB/SDS阴阳离子液胞的物理稳定性;但胆固醇添加量小于35mol%时并不足以使系统内的阴阳离子界面活性剂全部转换为稳定的液胞而有结晶物产生;当胆固醇添加量更少(10mol%)时能稳定存在的液胞数量更少,所以计数率明显下降。由这些结果可以推论胆固醇与阴阳离子界面活性剂在液胞的双层膜中是以固定比例排列存在,从而可以维持液胞的稳定性,因此胆固醇添加量较高时液胞稳定性较佳。     

双子表面活性剂的NMR研究现状与展望

双子表面活性剂是一类新型的表面活性剂, 其分子由化学键通过联接基团将两个单链表面活性剂的离子头联接构成. 由于其结构的特殊性, 使其具有特殊的性质, 如高表面活性, 特殊的聚集形态等. 多年来的研究结果表明, 联接基团的结构和长度对双子表面活性剂的活性影响最大. 与其它研究手段相比, NMR在从分子水平上研究双子表面活性剂溶液中胶束的形成以及自聚集状态, 有着独特的优势.     

表面弹性和分离压耦合作用下的垂直液膜排液过程

针对含不溶性活性剂的垂直液膜排液过程,在考虑表面弹性和分离压耦合作用的基础上,采用润滑理论建立了液膜厚度、表面速度和活性剂浓度的演化方程组,通过数值计算分析了表面弹性和分离压单独作用和耦合作用下的液膜演化特征.结果表明:表面弹性与分离压均对垂直液膜排液过程有显著影响.表面弹性单独作用时,液膜初始厚度随弹性增大,黑膜仅在液膜顶部形成,长度较短且不能稳定存在;分离压单独作用时,活性剂随流体不断汇集在底端,液膜表面无法形成表面张力梯度,不发生逆流现象;当二者耦合作用时,可得到较稳定的液膜,排液前期增加表面弹性可提高液膜的厚度、降低表面速度和促使液体逆流,从而减缓排液过程;后期出现黑膜后,分离压中的静电斥力起主要作用,延缓液膜"老化".     

SiO2纳米颗粒单层膜流变特性的双Wilhelmy片法研究

本文采用两个互相垂直的Wilhelmy片对不同润湿性的SiO₂纳米颗粒单层膜的表面压和黏弹性进行了研究, 并利用Brewster角显微镜(BAM)对单层膜的形貌演变进行了观测. 实验发现, 当水面完全被颗粒覆盖时, 单层膜的表面压具有明显的各向异性, 中等润湿性(34%SiOH)的颗粒膜其表面压各向异性最大. 压缩模量E和剪切模量G均在中等润湿性时出现最大值. 这些结果表明, 单层膜的流变性能与泡沫的稳定性密切相关. 疏水性最强(20%SiOH)的颗粒膜具 关键词： 纳米颗粒 单层膜 表面压 流变     

杂双子咪唑表面活性剂的合成及其表面性能

合成了一系列以两个亚甲基为联接基的杂双子咪唑表面活性剂([C_m-2-C_nim]Br_{2, m, n}=8, 10, 12, 14, 16; m≠n). 用氢谱和质谱对其结构进行了表征. 探索了物料比、反应温度和时间对反应产率的影响. 对合成的杂双子咪唑表面活性剂的表面活性进行了研究,讨论了分子结构的不对称程度对表面活性的影响.     

表面活性剂及水溶性功能高分子的NMR研究

核磁共振（NMR）技术是研究表面活性剂在溶液中聚集状态的一种非常有用的工具,本文运用多种NMR技术研究了几种不同类型表面活性剂及水溶性功能高分子在水溶液中的聚集行为： 1. 季铵盐型双子表面活性剂16-4-16的聚集行为季铵盐型双子表面活性剂N,N′-双(十六烷基二甲基)-α,ω-丁烷溴化铵(16-4-16)分子中联接基团及靠近离子头的质子位于胶束的壳层, 运动受到一定限制. 而距离离子头较远的烷烃链位于胶束的内部,运动相对自由. 与对应的单链表面活性剂十六烷基三甲基溴化铵(CTAB)相比,16-4-16形成的胶束堆积更为紧密. 通过NOESY谱中交叉峰强度的定量计算,认为16-4-16在胶束中分子以上下交错排列的方式形成球形聚集体.  2. 脱氧胆酸钠与十六烷基三甲基溴化铵的相互作用在脱氧胆酸钠(NaDC)溶液中,NaDC质子H3与其他质子不同,其横向弛豫时间(T₂)表现为双指数衰减,表明此质子可能存在两种不同的状态. 实验证明,其它胆酸盐的H3的横向弛豫也呈现双指数衰减. 因此推测在胆酸盐的稀溶液中,3-OH质子和羰基氧之间有可能存在氢键作用,形成了头尾相连的分子对结构.  在NaDC和CTAB的混合溶液中,两者形成1∶1的混合胶束. 用NOESY和ROESY研究混合胶束的结构,显示CTAB的离子头位于NaDC的羧酸基团附近. 这可能是正负离子之间的静电性相互作用的结果.  3. 丙烯酰胺/丙烯酸模板共聚物的微结构研究了不同pH值条件下,丙烯酰胺和丙烯酸共聚物分子在水溶液中的聚集形态. 在酸性溶液中,分子内的氢键致使聚集体形成较为紧密的堆积,侧链的苯氧基团运动受阻;随着溶液pH值的增大,丙烯酸电离产生的阴离子使得分子间的静电斥力增大,分子链变得伸展,分子间的氢键作用导致了聚集体体积变大. 当溶液呈强碱性,丙烯酸完全电离,氢键作用力被破坏,分子呈现自由伸展的状态,侧链的苯氧基团运动相对自由.     

Adsorption of dissymmetric cationic gemini surfactants at silica/water interface

Adsorption of a series of cationic gemini surfactants 12-2-m (m = 8, 12, 16) on the surface of silica was investigated. The critical micelle concentrations, cmcs, of cationic gemini surfactants in the initial solutions and in the supernatants were measured by conductometry and tensiometer. The changes in cmc values indicate that the ion exchanges take place between polar groups of gemini surfactants adsorbed and ions bound on the surface of silica. The adsorption isotherms of cationic gemini surfactants were obtained by a solution depletion method. Based on the driving force, the adsorption includes two steps, one of which is ion exchange, and the other is hydrophobic interaction. In each step, the tendency of surfactant molecules in the solution to form aggregates or to be adsorbed on the silica varies with their structures. The maximum adsorption amount of gemini surfactants on the silica, τ_max, decreases as increasing in the length of one alkyl chain, m, from 8, 12 to 16. So the results show that the adsorption behaviors of gemini surfactants are closely related to the dissymmetry of gemini molecules.     

LB膜的XPS光谱及其电致发光

采用X射线光电子能谱 (XPS)和UV Vis光谱研究了 2个以 8 氨基喹啉为亲水头基的两亲配体 ;2 长链烷基丙二酸二 (8 氨基喹啉 )酰胺 (H2 A) (H2 A1 2 :长链烷基为十二烷基 ;H2 A1 6 :十六烷基 )在气 /水界面与Cu2 离子的配位作用。配位后H2 A1 2 和H2 A1 6 单分子膜的崩溃压分别由 12 5和 15 6mN·m- 1 增加至 2 8 0和33 8mN·m- 1 。从含Cu2 离子亚相表面组装的LB膜出现了Cu2 离子的特征XPS峰 ,Cu2p为 935和 95 5eV ,XPS表明H2 A与Cu2 的配位比为 1∶1。H2 A的LB膜可以用作电致发光 (EL)器件的空穴传输材料 ,三层EL器件ITO/TPD/LB膜 /Alq3/Al(LB膜分别为 15层H2 A1 2 和 15层H2 A1 6 )的驱动电压分别为 6 5和 7 5V ,最大亮度分别为 6 2 1和 2 0 1cd·m- 2 。     

Molecular organization of phospholipid monolayers on the water surface by Maxwell displacement current measurement

The monolayer of organic molecules at the air-water interface has been studied using the Maxwell displacement current (MDC) technique. The materials used in this study were the biological materials of phosphatidyl ethanolamine (PE) and phosphatidic acids (PA). The configuration of the experimental set-up consists of the metal/air-gap/monolayer/metal coupled with the Langmuir method. This measurement enables the detection of current without destroying the monolayer. The phase transition and molecular orientation of the phospholipid monolayers were investigated using MDC measurement without mechanical contact between electrodes and the materials. Direct evidence of phase transition from gaseous to the polar ordering phase can be obtained across phospholipid monolayers even though at very low surface pressure. Relaxation process of the phospholipid monolayers was investigated by using the step compression on the MDC signals.     

Surfactant-induced surface freezing at the alkane-water interface

Long-chain alkanes exhibit surface freezing at the alkane-air but not the alkane-water interface. Ellipsometry and surface tensiometry are used to show that a simple cationic surfactant, hexadecyltrimethylammonium bromide (CTAB), can induce surface freezing at the tetradecane-water interface even when present in mole fractions as low as 0.1. The surface-freezing temperature T(s) is a linear function of the interfacial excess of CTAB. The excess surface entropy below T(s), S(sigma)=-0.76+/-0.02 mJ K-1 m(-2), is consistent with a rotator phase. Ellipsometry provides strong evidence for a frozen monolayer in which the chains are oriented near the surface normal.     

Surface pressure anisotropy and complex relaxation of silica nanoparticle monolayer at the air-water interface

We report the anisotropy effect and the relaxation dynamics of surface pressure of silica nanoparticle monolayer at the air-water interface. The anisotropy of surface pressure occurs when the water surface is fully covered by particles and becomes more prominent with the increase of surface concentration. Hence, the conception of surface tensor was proposed to characterize the monolayer properties. The dynamics of pressure relaxation involves three timescales which are related to the damping of surface fluc...     

Investigations of RhB Langmuir monolayer by Fluorescence Imaging Microscopy

This communication reports the surface pressure vs area per molecule isotherm and Fluorescence Imaging Microscopic studies of the formation of domain structure in the mixed Langmuir monolayer of RhB and Stearic acid (SA) at the air-water interface. Strong repulsive interaction between the unlike components leads to the phase separation and formation of microcrystalline domains at the air-water interface of the Langmuir monolayer. These domains can be directly visualized using fluorescence imaging microscope.     

Novel surface tension isotherm for surfactants based on local density functional theory

In this Letter we report a new general method for calculating of surface tension isotherms in the presence of surfactants, based on a local density functional. We illustrate this method by deriving the interfacial tension isotherm for nonionic surfactants at an air-water or oil-water interface by using the self-consistent field theory of polymer brushes. We consider a particular case of local density functional to calculate explicitly how the interfacial tension and the surfactant adsorption depend on the surfactant bulk concentration. Experimental data for the surface tension and the surfactant adsorption isotherm for nonionic surfactants were interpreted with the help of the new isotherm. Very good agreement between the adsorption of n-dodecyl pentaoxyethylene glycol ether (C12E5) at an air-water interface, calculated from the surface tension isotherm and small-angle neutron-scattering is obtained.     

硬脂酸单分子膜上电沉积Ag膜的研究

通过电沉积方法 ,以气 /液界面上形成的硬脂酸单分子膜为模板诱导沉积金属银膜 .考察了镀液 pH值、单分子膜表面压及沉积电位对银膜形貌及结构的影响 .实验发现 ,酸性镀液的气 /液界面上形成的单分子膜不能诱导沉积银 ,而在中性和碱性镀液的气 /液界面上可以诱导银膜的生长 .当单分子膜处于液态或固态时 ,气 /液界面有银膜形成 ;液态单分子膜上的银膜生长速度较快 ,且银膜的结构一致 .随着电极电位的升高 ,银膜沉积的速度加快 ,呈环状向外生长的圆形银膜逐渐变得不规则 .将不同实验条件下的银膜转移出来 ,采用扫描电镜 (SEM )、透射电镜 (TEM )对银膜的结构与形貌进行了表征 .研究表明 ,银首先在单分子膜上异相成核 ,由八面体构型逐渐发展成星型 ,最终在气 /液界面形成具有松枝状微观结构的光亮银膜 .     

Electrostatic origin of the Frank elastic energy and anisotropic line tension of the domains in monolayers at the air-water interface

The free energy of condensed phase domains in monolayers at the air-water interface has been analyzed by taking into account the surface pressure, line tension, and electrostatic energy due to the normal and in-plane spontaneous polarization. We found that this free energy was reduced to the sum of the Frank elastic energy and anisotropic line tension, which were used to reproduce the shapes of domains in fatty acid monolayers, in the limit of small orientational deformation. Domains in monolayers are interesting systems as a meeting point between the physics of liquid crystals and electrostatics.     

Phase transitions in Langmuir monolayers

Some fatty acids, lipids, polymers and mesogenic molecules which are amphiphilic in nature spread at the air-water interface to form stable Langmuir monolayers. They exhibit a rich variety of two-dimensional (2D) phases. In this article, we briefly review some of the novel features we have found in these monolayers. For example, we find transition from a 2D monolayer to three-dimensional structures possessing liquid crystalline order, induced liquid condensed phase, demixing of liquid expanded phase, critical points and pattern formation.