高分子与表面活性剂在水相中的相互作用

按照组分荷电属性的不同,高分子/表面活性剂体系可大致划分为三种:中性高分子/离子表面活性剂体系、带电高分子/离子表面活性剂体系、高分子/非离子表面活性剂体系。本文对这三种体系在水相中的高分子/表面活性剂相互作用研究进行综述。在大多数情况下,水相中高分子与表面活性剂共存时都能发生相互作用并形成复合物,其驱动力主要包括疏水作用、静电作用和氢键作用。根据高分子与表面活性剂的荷电情况及结构性质(如疏水链长度)的不同,上述驱动力可以单独或组合作用。此外,温度、pH值、电解质等外界因素对复合物形成过程及结构也具有不同程度的影响。     

DNA与表面活性剂相互作用研究(Ⅱ)--基于构象变化的分子水平研究

综述了DNA在稀溶液中与表面活性剂在分子水平上的相互作用的研究进展。介绍了DNA与表面活性剂的两阶段键合过程以及伴生的DNA由线圈向小球的构象变化及其理论解释。同时阐述了相关的对其微观构象变化的研究方法，如热变性实验、荧光光谱、荧光显微技术、动静态光散射等。对DNA与表面活性剂形成的复合物作为基因转染载体的前景及限制因素作了简要介绍。     

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。     

DNA与表面活性剂的相互作用（I）——基于相行为的宏观研究进展

综述了以相行为为基础的DNA与表面活性剂在水及有机溶剂中相互作用的研究进展及其相关研究方法。阐述了静电作用及疏水作用对相行为的影响。介绍了用光散射法及浊度法确定沉淀边界和用键合等温线及恒温滴定量热法考察DNA与表面活性剂相互作用的键合度及协同键合过程的能量变化，以及利用短链DNA与表面活性剂复合物在固体表面的吸附等温线来考察沉淀后复合物的构象变化。     

DNA与表面活性剂的相互作用(Ⅰ)--基于相行为的宏观研究进展

综述了以相行为为基础的DNA与表面活性剂在水及有机溶剂中相互作用的研究进展及其相关研究方法.阐述了静电作用及疏水作用对相行为的影响.介绍了用光散射法及浊度法确定沉淀边界和用键合等温线及恒温滴定量热法考察DNA与表面活性剂相互作用的键合度及协同键合过程的能量变化,以及利用短链DNA与表面活性剂复合物在固体表面的吸附等温线来考察沉淀后复合物的构象变化.     

可生物降解肝素钠/两性壳聚糖复合物用于蛋白药物pH响应释放研究

制备了一类可生物降解肝素钠两性壳聚糖复合物(HPACS),并探索将其用于蛋白药物pH响应释放.两性壳聚糖由壳聚糖与丙烯酸加成反应得到,丙烯酸取代度可通过丙烯酸壳聚糖投料比调控;用胶体与pH浊度滴定研究了肝素钠与两性壳聚糖的复合作用,发现两组分在一定pH范围内能通过静电相互作用形成复合物,复合转变临界pH(pHΦ)与两性壳聚糖中丙烯酸取代度有关,取代度越低,pHΦ值越高.以牛血清白蛋白(BSA)为模型,测定了其在复合物中包埋及不同pH介质中的释药行为.结果表明,BSA可以在非常温和条件下有效包埋于复合物中,包埋率接近100%;BSA从复合物中释放具有很高的pH响应性,释放转变在很窄的pH范围内(<0.4pH单位)完成,释放转变临界pH(pH′Φ)可由两性壳聚糖中丙烯酸取代度调控.复合物形成和蛋白质释放在对pH依赖性上存在很好的相关性.同时还发现,在中性介质中(pH7.4),复合物对BSA具有很好的缓释作用,BSA持续释放时间可达15天左右.     

电解质和乙醇对DNA与Gemini表面活性剂相互作用的影响

应用荧光探针和zeta电位方法研究了电解质NaBr、NaCl、KCl和有机溶剂乙醇对DNA与Gemini表面活性剂相互作用的影响. DNA诱导的表面活性剂类胶束在较低浓度即可生成, 这一浓度称为临界聚集浓度(CAC). Gemini表面活性剂比具有相同烷烃链长的单体表面活性剂更易聚集, 对应的CAC较低. 实验结果表明, 盐(NaBr)浓度对DNA/表面活性剂体系的CAC影响不大, 阴、阳离子的种类则对该体系有不同程度的影响. 阴离子(Br-、Cl-)对体系的CAC有显著的影响, 但阳离子(Na+、K+)的差异对CAC影响不大. 极性溶剂乙醇对DNA与表面活性剂相互作用的影响比较复杂. 乙醇浓度较低时有利于表面活性剂的聚集, 使得CAC减小; 而浓度较高时, 则不利于表面活性剂聚集,从而使CAC变大. 乙醇可显著改变DNA/表面活性剂复合物的zeta电位.     

表面活性剂中DNA构象变化的研究

以荧光探针法研究了表面活性剂与小牛胸腺DNA的相互作用，结果表明：阳离子表面活性剂主要通过静电引力和疏水方式与DNA作用；阴离子表面活性剂与DNA之间存在静电排斥力，两者之间的相互作用不太明显；而非离子表面活性剂与DNA的相互作用类似于有机溶剂对DNA的影响，即通过溶液的极性、粘度和介电常数来影响DNA的构象，表面活性剂使得DNA构象发生较大的变化，预示了它可能使DNA的生物功能发生较大的变化。     

两性高分子与小分子及大分子的相互作用（下）

2 两性高分子与染料及表面活性剂的相互作用文献中对阳离子聚电解质、阴离子聚电解质及非离子性高分子与染料、去污剂、表面活性剂等小分子物质的相互作用有较多报道,而有关两性高分子与这些小分子物质相互作用的报道极少。本节就合成两性高分子与染料等小分     

两性聚电解质PDMA_m-b-PAA_n与表面活性剂(12-6-12)的相互作用

采用Zeta电位、荧光探针、表面张力和黏度等方法研究了碱性条件下不同嵌段比的两性聚电解质聚(N,N-二甲胺基甲基丙烯酸乙酯-b-丙烯酸)(PDMAm-b-PAAn)与阳离子偶联表面活性剂(C12 H25(CH3)2N(CH2)6N(CH3)2C12H25·2Br-)(简称12-6-12)的相互作用.结果表明:由于静电相互作用,两嵌段聚电解质PDMAm-b-PAAn和12-6-12之间可形成类胶束或复合物,PDMA链段的弱亲水性对复合物起到稳定的作用.对同一类型的两嵌段聚电解质,改变两链段的相对长度之比,既不会使其在溶液中的构象发生改变,也不会使其与表面活性剂的相互作用模式发生改变.     

Use of surfactants to remove water-based inks from plastic film: effect of calcium ion concentration and length of surfactant hydrophobe

Effective plastic film deinking could permit the reuse of recycled polymer to produce clear film, reduce solid waste for landfills, reduce raw material demand for polymer production, and aid process economics. In this study, the deinking of a commercial polyethylene film printed with water-based ink was studied using surfactants in the presence of hardness ions (calcium ions) at various pH levels. The electrostatic properties of ink particles in a washing bath were also investigated. Synthetic anionic surfactant or fatty acid soap in the presence of calcium ions at alkaline pH levels was found to be nearly as effective at deinking as cationic, nonionic, or amphoteric surfactants alone. However, adding calcium ions decreases the deinking effectiveness of cationic, nonionic, and amphoteric surfactants. Increasing the length of the ionic surfactant hydrophobe enhances deinking. Zeta potential measurements showed that water-based ink particles in water reach the point of zero charge (PZC) at a pH of about 3.6, above which ink particles are negatively charged, so cationic surfactant tends to adsorb better on the ink than anionic surfactant above the PZC in the absence of calcium. As the cationic surfactant concentration is varied between 0.005 and 25 mM, the zeta potential of the ink particles reverses from negative to positive owing to adsorption of cationic surfactant. For anionic surfactants, added calcium probably forms a bridge between the negatively charged ink and the negatively charged surfactant head groups, which synergizes adsorption of the surfactant and aids deinking. In contrast, calcium competes for adsorption sites with cationic and nonionic surfactants, which inhibits deinking. All the surfactants studied here disperse ink particles effectively in the washing bath above pH 3 except for the ethoxylated amine surfactant.     

Microfiltration of amphoteric surfactant using ceramic membranes

The microfiltration of commercially available amphoteric surfactant using ceramic membranes has been investigated. Various combinations operating conditions such as pH, electrolyte and surfactant concentrations were employed. Zeta potential and adsorption isotherms were obtained for the components of membrane surfactant system as functions of pH using surfactant or indifferent electrolyte (KCl). The shift in the membrane isoelectric point induced by the surfactant is linked to the carboxylic groups present on the surfactant which are believed to play a dominant role in the net surface charge of the membrane. A minimum in the permeate flux was found at the pH corresponding to the isoelectric point of the zwitterionic surfactant. This behaviour is ascribed to the interactions occurring between the surfactant–surfactant molecules and the surfactant–membrane. The higher fluxes obtained at low pH as compared to high pH arise from different fouling mechanisms and ionic strengths. Lower fluxes were found when inorganic electrolytes were used in conjunction with surfactant. However, as the valency of the salt increases, flux behaviour of the zwitterionic surfactant (close to isoelectric point) does not vary whilst the cationic and anionic state of the surfactants are much more affected. Interactions between surfactant molecules as a result of the charge screening effects by the larger valence ions are encouraged. The permeate flux declines with an increasing surfactant concentration even though some concentrations fall under the critical micelle concentration (c.m.c.). This is attributed to concentration polarisation in which the accumulated surfactant concentration at the membrane surface could form a stable viscous phase which is resistant to permeate flow in the secondary layer next to the membrane surface. This paper demonstrates the role interactions such as surfactant–surfactant and surfactant–membrane play in influencing the filterability of surfactant solutions using ceramic membranes.     

纳米SiO2/十二烷基氨基丙酸钠协同稳定的pH响应性Pickering乳状液

用纳米SiO₂颗粒与微量氨基酸型两性表面活性剂十二烷基氨基丙酸钠作复合乳化剂, 以正癸烷为油相, 制备了pH响应性O/W型Pickering乳状液. 室温下该乳状液在pH≤4.0 时稳定, 在pH≥6.0时不稳定, 因此, 可以通过改变水相的pH值使乳状液在稳定和破乳之间多次循环. 在酸性水介质中, 氨基酸型两性表面活性剂分子呈阳离子状态, 可通过静电作用吸附到带负电荷的SiO₂颗粒表面, 产生原位疏水化作用, 使其转变为表面活性颗粒; 而在中性和碱性水介质中, 氨基酸型两性表面活性剂呈两性或阴离子状态, 不能产生原位疏水化作用, 因而导致乳状液破乳. 相关作用机理通过吸附量、 Zeta电位及接触角等实验数据得以论证. 该刺激-响应性Pickering乳状液在乳液聚合、 油品输送以及燃料生产等领域具有重要的应用价值.     

Photoluminescence of ZnO nanoparticles prepared by laser ablation in different surfactant solutions

ZnO nanoparticles were prepared by laser ablation of a zinc metal plate in a liquid environment using different surfactant (cationic, anionic, amphoteric, and nonionic) solutions. The nanoparticles were obtained in deionized water and in all surfactant solutions except the anionic surfactant solution. The average particle size and the standard deviation of particle size decreased with increasing amphoteric and nonionic surfactant concentrations. With the increase of the amphoteric surfactant concentration, the intensity of the defect emission caused by oxygen vacancies of ZnO rapidly decreased, while the exciton emission intensity increased. This indicates that anionic oxygen in the amphoteric surfactant molecules effectively occupied the oxygen vacancy sites at the ZnO nanoparticle surface due to charge matching with the positively charged ZnO nanoparticles.     

Synthesis of pH-responsive particles with shape anisotropy

Seeded emulsion polymerization is used to produce large quantities of shape anisotropic, amphoteric particles in a size range of about 1 μm. Copolymer dicolloids (CDCs) containing pyridine groups are synthesized by swelling spherical, lightly cross-linked polystyrene seeds with a mixture of styrene and pH-responsive monomer 2-vinyl pyridine followed by secondary polymerization to contrast with their analogue homopolymer dicolloids (HDCs) where the swelling step is carried out with styrene alone. After the particles are coated with a nonionic surfactant to minimize van der Waals attractions, surface potentials and aggregation properties of dilute suspensions are studied as functions of pH and ionic strength. Compared to HDCs, which remain stable at all pH values studied (3 < pH < 9) up to an ionic strength of 5 M, the CDC particles show amphoteric behavior with strong attractions under conditions where dipolar interactions are expected to dominate.     

Micellar Interactions in Nonionic/Ionic Mixed Surfactant Systems

To study the influence of the chemical nature of headgroups and the type of counterion on the process of micellization in mixed surfactant systems, the cmc's of several binary mixtures of surfactants with the same length of hydrocarbon tail but with different headgroups have been determined as a function of the monomer composition using surface tension measurements. Based on these results, the interaction parameter between the surfactant species in mixed micelles has been determined using the pseudophase separation model. Experiments were carried out with (a) the nonionic/anionic C(12)E(6)/SDS ((hexa(ethyleneglycol) mono-n-dodecyl ether)/(sodium dodecyl sulfate)), (b) amphoteric/anionic DDAO/SDS ((dodecyldimethylamine oxide)/(sodium dodecyl sulfate)), and (c) amphoteric/nonionic C(12)E(6)/DDAO mixed surfactant systems. In the case of the mixed surfactant systems containing DDAO, experiments were carried out at pH 2 and pH 8 where the surfactant was in the cationic and nonionic form, respectively. It was shown that the mixtures of the nonionic surfactants with different kinds of headgroups exhibit almost ideal behavior, whereas for the nonionic/ionic surfactant mixtures, significant deviations from ideal behavior (attractive interactions) have been found, suggesting binding between the head groups. Molecular orbital calculations confirmed the existence of the strong specific interaction between (1) SDS and nonionic and cationic forms of DDAO and between (2) C(12)E(6) and the cationic form of DDAO. In the case for the C(12)E(6)/SDS system, an alternative mechanism for the stabilization of mixed micelles was suggested, which involved the lowering in the free energy of the hydration layer. Copyright 2000 Academic Press.     

Effect of electrical potential on the electro-demulsification of oily sludge

Oily sludge, produced mostly in petroleum refineries and petrochemical industries, is one of the major industrial wastes that require treatment. Typically, these sludge wastes are water-in-oil emulsions that are stabilized by fine solids. These fine particles adsorb at the droplet surface and by lowering the demulsification rate constant, act as a barrier to prevent droplet coalescence. In this investigation, the effects of different electrical potential gradients and amphoteric surfactant on effectiveness of phase separation were investigated. It was concluded that lower electrical potential (0.5 V/cm) produced a higher demulsification rate. The solid phase remaining after the experiment was of a more compact and stable consistency. It was concluded that application of the amphoteric surfactant does not improve the total efficiency of the process. The role of oil constituents in stabilizing water-in-oil emulsions, and their effect on the dynamics of the process, were considered in every step of the experiment. Analysis of pH changes, resistance evolution, and hydrocarbon polarity analysis confirmed that the application of lower electrical gradient results in better phase separation.     

Synthesis of polystyrene latex with amphoteric surfactant and its characterization

An emulsion polymerization of styrene in the presence of an amphoteric surfactant; N,N-dimethyl-n-laurylbetaine (LNB) was carried out at pH 7.0. The polymerization rate and the concentration of the latex particle were proportional to the LNB concentration of 0.6 power. The latex particle sizes became smaller with increasing concentrations of LNB. The molecular weights of polystyrene latices increased with the concentration of LNB. The zeta-potentials of latex particles were significantly dependent on the pH, and showed the existence of an isoelectric point.     

Deposition of Oil Drops on a Glass Substrate in Relation to the Process of Washing

The attachment of emulsion drops to glass substrates is investigated in relation to the redeposition of oil drops in the process of washing. It turns out that the drops of a surfactant-stabilized oil-in-water emulsion cannot be attached to an immersed glass plate simply by the buoyancy force. However, the same drops can be deposited on the plate when the latter is pulled out of the emulsion, i.e., when the drops are pressed against the substrate by a receding meniscus. We measured the amount of the oily deposit as a function of the pH, ionic strength, and composition of an amphoteric-anionic surfactant mixture. The enhanced oil deposition at low pH correlates with the domain in which the emulsion drops and the solid substrate bear opposite electric charges. This was established by zeta-potential measurements with oil drops and glass particles. The anionic surfactant brings negative surface charge to the oil droplets and suppresses the oil deposition on the negatively charged glass. With the increase of the fraction of the amphoteric surfactant in the mixture, the zeta-potential is converted from negative to positive, and the oil deposition grows almost linearly with the potential. In general, the deposition of oil drops by a receding meniscus is governed by an interplay of electrostatic and hydrodynamic factors. Copyright 2000 Academic Press.     

Separation of nucleic acid precursors on an amphoteric surfactant modified monolith using combined eluent flow, pH and concentration gradient

An RP monolithic column coated with an amphoteric carboxybetaine type surfactant has been used with a combined triple eluent concentration, pH and flow gradient ion chromatography technique for the simultaneous separation of up to 18 nucleotides, nucleosides and nucleobases. The separation of up to eight precursors on a 1 cm long monolithic microcolumn using the combined gradient approach is also shown. The method was applied to the separation of the above nucleic acid precursors in perchloric acid extracts of yeastolates samples.