离子型表面活性剂在水溶液中的分子构型

本文利用表面活性剂分子中内在的荧光探针及外加荧光探针,研究了离子型表面活性剂分子在水溶液中的构型,烷基三苯基鱗盐及N-烷基吡啶盐对芘的单体荧光猝灭服从Stern-Volmer方程,是扩散控制的碰撞猝灭,但不同链长的猝灭剂的荧光猝灭行为呈反常状态,即链越长,猝灭速率常数越大,在十六烷基三甲基铵(CTMAB)水溶液中观察到了芘的激基缔合物荧光,同时观察到了CTMAB对芘的荧光猝灭的阻碍(阳离子猝灭剂)和促进(阴离子猝灭剂)作用,提出离子型表面活性剂在水溶液中呈绕曲状的分子构型,且是一种动态构型。     

CMC系列高分子表面活性剂的胶束形态

高分子表面活性剂分子量高 ,分子中兼具亲水和疏水链段 ,在选择性溶剂水中同小分子表面活性剂一样 ,可形成疏水链段为核心、亲水链段为外壳的胶束结构 ,但高分子量又使其表现出许多不同于低分子表面活性剂的形态特征 ,如胶束的多种形态、尺寸分布多分散性等等 ,而这些形态特征对高分子表面活性剂的界面活性、增粘、乳化等性能有决定性的影响．结构规整的嵌段或接枝共聚物在选择性溶剂中的分子聚集形态已有研究 ［１,２］,亲水亲油性的高分子表面活性剂在水溶液中由于结构复杂、水溶液中氢键作用及静电作用力等因素造成的困难 ,因而研究较少…     

含Schiff碱基囊泡双分子膜的聚集结构与相变

研究表面活性剂分子在水溶液中的聚集行为对模拟生物膜功能和研究分子间相互作用具有重要意义"'．用于形成囊泡双分子层的表面活性剂主要是类似天然磷脂的双烷基链两亲分子,单烷基链两亲分子在引人刚性基团时亦可形成双分子膜k'．含SChiff碱基两亲分子在水溶液中的聚集性质及间、尾链长度对SChiff碱基构象的影响已有报道"'．本文报道了这类分子的另一种重要成膜性质,即改变制备条件,可选择性地得到不同聚集结构和相变温度的双分子膜·实验中所用成膜分子为：CH。（CH。）。;OPh-N-CH－PhO（CH;）n;N"（CH。）。Br－（m-4;n-…     

荧光桃红B在CTMAB上Langmuir吸附及阳离子表面活性剂测定新技术

在离子型表面活性剂溶液中 ,电荷均匀分布在分子长链并形成点静电场 ,容易吸附带异性电荷的探针色体。研究了利用微相吸附 光谱修正 (MPASC)技术分析溴化十六烷基三甲胺(CTMAB)与荧光桃红B(PB)的结合反应 ,并分析了表面活性剂在微量分析中的增效机理。结果表明 ,PB CTMAB作用符合Langmuir单分子层吸附 ,产物结合比为 2∶1,结合常数为 3.4 6× 10 5(15°) ,摩尔吸光系数 (5 6 5nm)ε =1.14× 10 5L·mol- 1·cm- 1,胶束聚集态 (PB2 CTMAB) 78,定量测定了样品中阳离子表面活性剂含量 ,结果良好     

水溶液中的分子内扭转电荷转移──阴阳离子胶束中对二甲基氨基苯甲酸分子内扭转电荷转移的比较研究

在阳离子表面活性剂CTMAB水溶液中,对二甲氨基苯甲酸(DMABOA)的分子内扭转电荷转移(TICT)荧光带随着胶束的形成而显着蓝移,同时伴随着TICT荧光带与正常荧光带强度比I_a/I_b和总荧光强度I_f的增大;而阴离子表面活性剂SLS胶束的形成并未引起TICT荧光带位置和I_a/I_b的变化,仅使I_f提高(较在CTMAB胶束中的小).实验发现在胶束疏水核中的TICT行为与纯有机溶剂中不同,DMABOA与CTMAB胶束的疏水相互作用和静电作用是协同的。     

荧光探针法确定胶束的宏观结构参数

胶束是表面活性剂分子在溶液(水溶液或非水溶液)中簇集而成的。在表面活性剂的临界胶束浓度(cmc)以上不太高的浓度范围内,胶束的结构被认为是球状的。水溶液中胶束的结构示于图1。近年来胶束在模拟酶、催化反     

正负离子表面活性剂与两性表面活性剂的相互作用

本文研究正负离子表面活性剂与两性表面活性剂混合水溶液的表面性质, 以及两性表面活性剂对正负离子裘面活性剂溶解度的影响。结果表明: (1) 两性表面活性剂的加溶作用,有助于正负离子表面活性剂的溶解; (2) 加入两性表面活性剂的量适当, 混合溶液基本保持原正负离子表面活性剂的表面活性; (3) 正负离子表面活性剂与两性表面活性剂在表面层和胶团中分子间的相互作用比正负离子表面活性剂与非离子表面活性剂分子间的相互作用稍强HC-FC正负; 离子表面活性剂与两性表面活性剂混合体系在表面层中有可能形成双分子或多分子层结构。     

碳氟表面活性剂与碳氢表面活性剂混合水溶液的表面吸附与胶团形成(Ⅳ)——非离子-非离子体系

测定了25℃不同比例的C₁₀F₁₉O(C₂H₄O)₉H与C₈H₁₇C₆H₄O(C₂H₄O)₁₀H混合水溶液的表面张力,研究混合水溶液的表面性质与胶团形成。用两种不同方法计算在表面上的表面成份、分子之间相互作用参数(β_σ)。结果表明,在非离子型碳氟和碳氢表面活性剂混合水溶液中,两种表面活性剂基本上各自形成胶团;表面分子相互作用参数皆为正值;表明此混合体系中碳氟链与碳氢链之间互疏作用的存在。     

表面活性剂在水溶液中性质的质子核磁共振研究

综述了质子核磁共振的几种方法在表面活性剂水溶液研究中的应用.自从上世纪六十年代以来的许多研究表明核磁共振的各种技术是研究表面活性剂溶液的有效手段.它可以提供表面活性剂在水溶液中的cmc、胶束的结构、尺寸、水化、加溶性质和位置，不同表面活性剂胶束之间的相互作用，以及胶束与生物分子和高聚物的相互作用.化学位移已经成为惯常方法，弛豫测量提供动态信息，自扩散系数测量是研究胶束尺寸的很好手段.近来由于核磁共振技术的不断发展，用于研究生物大分子的2D NOESY和HOESY也逐渐应用到研究表面活性剂聚集结构中.由此可以得到有关表面活性剂在水溶液中行为的分子水平信息，是其它谱学方法所不能及的.     

Gemini表面活性剂分子结构对其水溶液中聚集行为的影响

Gemini表面活性剂是通过联接基团将两个具有亲水亲油性质的两亲结构单元在其亲水头基上或靠近亲水头基处以共价键方式连接而成的一类表面活性剂。这类表面活性剂由于联接基团的引入具有比传统单链表面活性剂更高的表面活性,同时分子结构中更多的可调控因素使其在水溶液中表现出更为丰富的自聚集行为,而且分子不同部位结构的改变对分子内或分子间相互作用产生不同的影响,可实现通过分子结构的设计有效调控其自聚集能力和聚集体结构。本综述将从联接基团、烷基链、亲水头基、反离子和其它功能性基团这五个方面概述近些年Gemini表面活性剂水溶液中聚集行为方面的研究进展,总结人们对Gemini表面活性剂分子间相互作用规律的认识,期望对于进一步发展这类高效的表面活性剂体系提供有益的帮助。     

Phase transitions of monoglyceride emulsifier systems and pearlescent effects in cosmetic creams studied by C NMR spectroscopy and DSC

The present work investigates the phase transitions of monoglyceride emulsifier systems and pearlescent effects in cosmetic creams using ¹³C-NMR spectroscopy and DSC. The four phases of monoglyceride emulsifier systems – the coagel, gel phase, liquid-crystalline lamellar phase, and cubic phase – can be characterized in creams at appropriate temperatures by NMR spectroscopy. The phase transition temperatures were determined by DSC. Cross polarization (¹³C-CP)-magic angle spinning (MAS) measurements confirmed that the formation of the coagel is responsible for the pearlescence of creams. It could be shown that the proportions of monoglyceryl laurate and monoglyceryl myristate in the emulsifier system influence the phase transitions and the intensity of the pearlescence of creams. Furthermore, the coagel forms directly from the liquid-crystalline lamellar phase without transition through the gel phase if the cream is at a temperature higher than that of gel phase formation. These insights into the monoglyceride-emulsifier system of creams make it possible to more closely study the pearlescent effect of the coagel. Especially, the amount of emulsifier system in the coagel can be quantified. It could be shown that for a typical pearlescent cream more than 27% of the emulsifier system must be found in the coagel in order for pearlescence to be detectable optically. Moreover, the increase in the intensity of pearlescence over time after fabrication of a cream correlated with the increase in the amount of emulsifier system in the coagel. This ripening process can take up to approximately 15 months.     

Raman scattering spectra of sodium n-butyl(n-hexyl) phosphate aggregates and conformation about the phosphodiester PO bonds in coagel phases

A new double-chain surfactant molecule, sodium n-butyl(n-hexyl)phosphate (BHP), having an asymmetric molecular structure, has been synthesized. For anhydrous BHP in the solid state and the BHP---H₂O system in the lyotropic liquid crystalline and coagel states, the Raman scattering spectra arising from the accordion vibrational mode were studied in the temperature range −170 to 25°C. For anhydrous BHP, the GG form about the phosphodiester P---O bonds was preferentially stabilized at lower temperature. In the coagel phase of the BHP---H₂O system, preferential stabilization of a specific conformation about the P---O bonds occurred and which molecular form was stabilized was dependent on the water content: for the 8:2 BHP---H₂O sample in the coagel the GT form was stabilized, while for the 7:3 BHP---H₂O coagel sample the TT form was preferentially stabilized. The stabilization of such a specific conformation was also reflected in the higher-frequency region.     

十六烷基三甲基溴化铵水溶液热致相变的红外光谱研究

在280～320K的温度范围内考察了30％十六烷基三甲基溴化铵水溶液的红外光谱随温度的变化。结果表明该体系的凝聚胶-液晶相转变温度为300K。在300K以下的凝聚胶相,分子的极性头部基团处于高度“固定”的状态,分子的碳氢链以有序的相互平行方式排列,极性头与碳氢链之间有一定的倾斜角。在300K以上的液晶相,极性头内部CH_3-(N~+)基团以及整个极性头与碳氢链之间发生了旋转,碳氢链变为以六方亚晶胞填充形式存在,旦扭曲式构象异构体数量显著增多,极性头与碳氢链之间已不存在倾斜角,分子的亲水极性头和疏水碳氢链部分都处于“融化”状态。     

Thermal study of the interaction of crystalline surfactant with water; The dioctadecyldimethylammonium chloride-water system

Dioctadecyldimethylammonium chloride (DOAC) was completely dehydrated under high vacuum and at a temperature above its transition temperature (96.7°C) which was first discovered by us. Thermoanalytical studies on DOAC-water systems indicate that two successive phase changes of coagel → gel and gel → liquid crystal appear due to the increasing structural disorders of polar head groups and hydrocarbon chains, respectively. Furthermore, it is revealed that three types of water exist, i.e., bound, intermediate and free. On the basis of a bilayer-lamellar structure model, a predominant role of the intermediate water in these transitions is pointed out.     

芘为荧光探针研究SDS/H2O二元体系的热相变

以芘作为荧光探针, 对十二烷基硫酸钠(SDS)40 g%的水溶液在-20 ℃～30 ℃温区的相变进行了研究。该二元体系的主要相变是凝聚胶-液晶的转变, 测定其相变温度为20 ℃。自由水形成的冰层在0 ℃融化, 由此导致在化冰前后体系呈现出不同的凝聚胶相。在-17 ℃退火处理, 体系出现了新的凝聚胶相。以上出现的各相均可由I_E/I_M值清楚地表征, 从而首次证实了这种探针方法为一种成功的膜模拟体系相变的研究手段。     

Ultrasonic velocity measurements as a method for investigating phase transitions of monoglyceride emulsifier systems in pearlescent cosmetic creams

The phase transitions of monoglyceride emulsifier systems and pearlescent effects in cosmetic creams are investigated using ultrasonic velocity measurements. The transitions between the different phases of monoglyceride emulsifier systems--the coagel, liquid-crystalline lamellar phase, and gel phase--are detected in creams by changes in the ultrasonic velocity with variation of the temperature. The phase transition temperatures correspond to DSC results. Furthermore, the slope of the ultrasound velocity curve correlates with the amount of bound water in the different phases. These insights into the ultrasonic velocity properties of the monoglyceride emulsifier system of creams make it possible to more closely study the pearlescent effect of the coagel. The temperature domain of the short time reversibility of the pearlescence as well as the back-formation time of the coagel can be determined with this method, which enable the optimization of the formulation of pearlescent creams.     

Quantum-chemical study of tautomers of reduced forms of anthraquinone

The quantum-chemical method B3LYP/6-311G(d,p) was used to calculate structural parameters of four conformers of 9,10-dihydroxyanthracene, two conformers of 9-hydroxyanthrone, and the corresponding anions, dianion, and radical anion. The energy of 9,10-dihydroxyanthracene in a gas phase is higher and in aqueous solution lower than the energy of 9-hydroxyanthrone. The dianion can exist exclusively in a polarizable medium.     

Effect of pressure on the thermotropic phase behavior of surfactant assemblies in water

The temperature (T)—pressure (P) phase diagrams of aqueous solutions of a homologous series of cationic surfactants, tetradecyl- (C14TAB), hexadecyl- (C16TAB), and octadecyltrimethylammonium bromide (C18TAB), have been determined by observing the sudden change of the transmittance accompanying the phase transition under high pressure up to 160 MPa. Regarding three kinds of phase transitions which have been previously assigned by the differential scanning calorimetry (DSC) (S. Kaneshina and M. Yamanaka, J. Colloid Interface Sci.131, 493, 1989), all the transition temperatures were linearly elevated by applying pressure. The volume changes associated with the transitions were estimated from the Clapeyron—Clausius equation by using the values of the T—P slopes on the phase diagrams and of the transition entropies taken from the DSC study. A chemical potential vs pressure profile, of which slope reflects the partial molar volume, among the states of surfactant assemblies, i.e., micelle, gel, and coagel, was drawn schematically on the basis of the transition volumes. The phase boundary between the coagel phase and the micellar solution should be the critical solution line of the surfactant, representing the pressure dependence on the Krafft temperature. In the C18TAB-water system, the phase boundary line between the metastable gel and the supercooled micelle had a break point at 45 MPa, suggesting the existence of a new pressure-induced mesophase above 45 MPa. The metastable gel phase of C14TAB disappeared in the pressure range up to 160 MPa.     

Miscibility of sodium chloride and ionic surfactant in adsorbed film and aggregate

The adsorption, micelle formation, and salting-out of dodecylammonium chloride in the presence of NaCl were studied from the viewpoint of mixed adsorption and aggregate formation. The surface tension of aqueous solutions of a NaCl–dodecylammonium chloride mixture was measured as a function of the total molality and composition of the mixture. Judging from phase diagrams of mixed adsorption and aggregate formation, NaCl and dodecylammonium chloride are miscible in the adsorbed film and coagel particle at high NaCl concentrations due to specific (nonelectrostatic) interaction between dodecylamonium ion and the counterion, while they are immiscible in the micelle. The difference in miscibility among the oriented states was ascribed to the difference in geometry among the states and to the interaction between bilayers in a coagel particle. Miscibility and specific interaction are compared between the mixtures of NaCl with dodecylammonium chloride and sodium dodecylsulfate.     

Enantiomeric segregation in the gel phase of lipid bilayers

Enantiospecific interactions within a monoglyceride lipid bilayer are investigated using molecular dynamics simulations. Preferential homochiral interactions are observed in the gel phase, whereas no detectable enantiospecificity is seen in the liquid-crystal phase. On the basis of these results and available experimental data, a mechanism is proposed for the formation of the coagel phase of monoglycerides. Enantiomeric segregation in the gel phase is also discussed in terms of its possible implications for prebiological evolution and membrane raft function.