Wetting Films of the Aqueous Cationic Polyelectrolyte Solutions on Quartz

It was shown that the stability of the wetting films of aqueous cationic polyelectrolyte solutions on the flat quartz surface depends on solution concentration. At a low concentration, the films are stable owing to the electrostatic repulsive forces. At a high polyelectrolyte concentration, the films are unstable due to the hydrophobization of quartz and the appearance of the hydrophobic attractive forces in the films. In the intermediate concentration range, the films are metastable and their lifetime depends upon the competition between the electrostatic repulsive and hydrophobic attractive forces. Thus, the concentration of cationic polyelectrolyte substantially affects the wetting conditions of the quartz surface. This conclusion can also be extended to other solid surfaces negatively charged in aqueous solutions, which is inherent to the majority of natural materials.     

Precipitation Recovery of Rhenium(VII) from Aqueous Solutions with Coagulating Cationic Polyelectrolyte

Rhenium(VII) recovery from dilute aqueous solutions by coprecipitation with VA-212 cationic polyelectrolyte in the presence of nitrate ions was studied.     

Reverse Flow of Mixed Surfactant Solutions after Their Capillary Rise

The reverse flow (i.e., the efflux from glass capillaries occurring after the stop of capillary rise) of mixed aqueous solutions of nonionic (Triton X-100) and cationic (cetyl- and dodecyltrimethylammonium bromides) surfactants is studied. The effect of electrolytes (salts and acids) on the process kinetics and the wetting in these systems is investigated. Possible causes of the reverse flow are discussed. They are related to the peculiar features of the interaction of nonionic and cationic surfactants with glass and to the differences in the surfactant adsorption from quiescent and moving solutions. It is shown that the wetting by the mixed surfactant solutions, including its kinetics, can be controlled by the addition of electrolytes.     

Capillary Electrophoresis of Cationic Surfactants

Surfactants are important additives in many chemical processes and products. A wide range of surfactants exists, including anionic, cationic, nonionic and zwitterionic. Benzalkonium chloride (BAC) is a widely used cationic surfactant in pharmaceutical and health-care products since it possesses antiseptic and antibacterial properties.     

阳离子聚电解质对油污泥的絮凝作用机理

用高密度电荷阳离子聚电解质处理油污泥［１,２］,依靠其与粘土颗粒间的静电作用压缩污泥中固相颗粒的表面双电层,中和ζ电位,使其颗粒间斥力减小,引力增大,油污泥化学脱稳,致使粘土颗粒聚集絮凝成团块,油颗粒聚集,实现油、水、泥渣的三相分离．１　实验部分１．１　样品制备　现场采集的油污泥中油品含量１９％,固含量８％,体系漏斗粘度３７ｓ,密度１．０９ｇ／ｃｍ３．阳离子聚电解质（ＣＦ）、聚丙烯酰胺－丙烯酸β－羟基丙酯基三甲基氯化铵按文献［２,３］方法制备,平均分子量２．６０×１０６,阳离子电荷度４５％．阴离…     

Kinetics and Isotherms of Cationic Polyelectrolyte Adsorption on Quartz

The kinetics of the formation of quartz surface charge in the solutions of a cationic polyelectrolyte, poly(styrene-co-dimethyl aminopropylmaleimide) with the molecular mass M = 20000 is studied in the concentration range from 10^–5 to 0.5 g/l in 10^–4 M KCl background solution at pH 6.5. Quartz capillaries with the radius from 5 to 10 m and molecularly smooth surface are used as model systems. Characteristic times of the formation of the surface charge at equilibrium with the solution are calculated from the data on the kinetics of adsorption; these times are equal to 40–50 min for the region of electrostatic adsorption (before the surface charge reversal) and 20–25 min, for the region of hydrophobic adsorption upon the formation of the second adlayer. Based on the steady values of the surface charge, the isotherms and potentials of adsorption of cationic polyelectrolyte are calculated. Electrostatic adsorption isotherm is described by the Langmuir equation with the energy of molecular adsorption of 25.4kT. It is shown that, at polymer concentration above 10^–2 g/l, the conformation of adsorbed molecules ceases to be planar. However, even in this case, we succeed in calculating the surface charge using the Helmholtz and Gouy equations and applying the pressure drops at the capillary ends higher than 10 atm, when under the loading of increasing shear stress in the surface layer the conformation of adsorbed molecules approaches the planar shape. Based on the two-layer model of the formation of surface charge developed earlier, it is shown that the energy of hydrophobic adsorption is smaller than that of electrostatic adsorption and is equal to 17.7kT. Possible physical mechanisms of electrostatic and hydrophobic adsorption of cationic polyelectrolyte molecules on quartz are discussed.     

作为电极添加剂的阳离子聚电解质的合成及性能的研究

选择Ce(SO4)2·4H2O与H2NCSNH为引发体系,控制反应温度为40℃,反应时间为6 h等工艺条件,成功合成了一种新的质子交换膜燃料电池电极添加剂-阳离子聚电解质P(AM-DMDAAC),其分子量在0.8×104～1.3×104范围内.通过测试阳离子聚电解质的电导率和研究循环伏安、热失重实验;结果发现,阳离子聚电解质P(AM-DMDAAC)有良好的电化学性能和热稳定性.     

Ultrasonic Absorption in Aaneous Polyelectrolyte Solutions

Ohne Zusammenfassung     

Regeneration of VA-212 Cationic Polyelectrolyte Exhausted in Rhenium(VII) Recovery from Aqueous Solutions by Complexation-Ultrafiltration Technique

A procedure was developed for regeneration of VA-212 cationic polyelectrolyte exhausted in recovery of rhenium(VII) from aqueous solutions by complexation-ultrafiltration technique. The regeneration includes polyelectrolyte coagulation by displacement of perrhenate by nitrate anions, ultrafiltration, and dissolution of the filtered sediment with reducing agent.     

pH敏感阳离子聚电解质凝胶的溶胀和释药性能

共聚物;pH敏感阳离子聚电解质凝胶的溶胀和释药性能     

Formation of Se0 Nanoparticles in an Aqueous Cationic Polyelectrolyte

The nanostructures formed by reduction of Se(IV) in the selenite-ascorbate redox system in an aqueous solution of supermacromolecular polycation, poly[trimethyl(methacryloyloxyethyl)ammonium] methyl sulfate, were studied by static and dynamic optical scattering and flow birefringence.     

Quantitative Determination of Cationic and Nonionic Surfactants in Aqueous Solutions of Their Mixtures by Capillary Zone Electrophoresis

A method based on capillary zone electrophoresis is developed for a quantitative determination of cationic (dodecylpyridinium bromide) and nonionic (Triton X-100) surfactants absorbing in the UV region. The effect of the pH and ionic strength of the solution on the output time and shape of the resultant peaks is studied, and the optimal conditions of the analysis are determined. For both surfactants, the analytical signal (the area of the peak on the electrophoregram) is found to linearly depend on the concentration. It is established that the presence of a second surface-active component does not affect the signal of the surfactant analyzed; thus, surfactants may be quantitatively determined in both individual and mixed solutions. The method of capillary zone electrophoresis is shown to be applicable for determining the CMCs of surfactants.     

The Effect of Surface Charge on Adsorption of a Cationic Polyelectrolyte

The regularities of adsorption of a cationic polyelectrolyte, poly(diallyldimethylammonium chloride), on the surface of fused quartz are studied at different values of solution pH by capillary electrokinetics. It is shown that the polyelectrolyte adsorption on a negatively charged surface depends on the value of the surface charge and increases with its growth. At a low charge value (pH 3.8), the polyelectrolyte adsorption increases the quartz surface charge. The driving forces of the adsorption are both electrostatic interaction and forces of nonelectrostatic nature, probably hydrophobic interactions and a change in entropy due to the displacement of counterions from a double layer. The adsorption of poly(diallyldimethylammonium chloride) on quartz from alkaline and neutral solutions is irreversible, which indicates the key role of the electrostatic interaction. At low values of the surface charge, the nonelectrostatic interactions play the main role, thereby resulting in polyelectrolyte desorption.     

正离子Gemini表面活性剂/负离子聚电解质相互作用的研究

摘要 采用荧光探针法和电导法研究了正离子偶联表面活性剂(C₁₂H₂₅(CH₃)₂N-(CH₂)₆-N(CH₃)₂C₁₂H₂₅•2Br) (12-6-12• 2Br^－)和带相反电荷聚电解质聚丙烯酸钠(NaPA)的相互作用, 结果表明: 由于静电相互作用, 12-6-12•2Br^－和NaPA之间可以形成类胶束或复合物. 对比十二烷基三甲基溴化铵(DTMAB)与NaPA复配体系的荧光光谱, 发现偶联表面活性剂与NaPA的相互作用强于传统表面活性剂. 此外, 还研究了盐和醇对偶联表面活性剂/聚丙烯酸钠的复配体系微极性的影响, 发现盐和醇对表面活性剂在聚电解质上形成类胶束和复合物的溶解都有一定的促进作用.     

Modification of the Quartz Surface by the Adsorption of a Cationic Polyelectrolyte

A capillary electrokinetics method is applied to measure the electrokinetic potential of the surface of quartz capillaries during the continuous flow of the aqueous solutions of a cationic polyelectrolyte (PE). At a low polymer concentration (10^–5 g/l), the adsorption is determined mainly by the electrostatic forces and its kinetics, by the conformational rearrangement of adsorbed macromolecules. As the concentration of PE increases, the charge of quartz surface reverses; and further adsorption is due to the forces of hydrophobic and molecular attraction between macromolecules. The adsorption energy is estimated for this case. The charge reversal of the surface is associated with the presence of adsorption sites of two different types. At a low concentration of PE, the adsorption takes place on negatively charged sites of quartz surface. At higher concentrations of PE, after the neutralization of the surface, the adsorbed PE molecules become new adsorption sites, and the adsorption acquires two-layer character. After adsorption, the quartz surface is hydrophobized: the contact angle measured by the bubble method is close to 33°–34°.     

高分子电解质溶胶－凝胶相转移与溶剂效应

以溶质、溶剂间的协同作用作为高分子电解质体系的凝胶化条件，以松软粒子结构（Ｂｌｏｂ）间的三维逾渗的凝胶化模型，将高分子电解质体系的凝胶化分为松软粒子的形成和逾渗过程。结合海藻酸溶液的Ｃｕ２＋、Ｃａ２＋、Ｍｎ２＋和Ｃｏ２＋离子添加体系的凝胶化，分析了高分子电解质溶胶－凝胶相转移的实质，得到了体系相对粘度的临界指数ｋ＝０．９０～１．１４，与逾渗模型的预测值相吻合，探讨了松软粒子的形成对相转移临界点ｆｃ的影响，明确了临界点附近相对粘度的幂次公式ηｒｅｌ∝（ｆｃ—ｆ）－ｋ）的适用范围。     

Cationic Spherical Polyelectrolyte Brushes as Nanoreactors for the Generation of Gold Particles

Summary: If long polyelectrolyte chains are attached densely to colloidal latex particles, a spherical polyelectrolyte brush results. These spherical polyelectrolytes are dispersed in water and carry a high charge. We demonstrate that these systems can be used to immobilize ions of heavy metals, such as gold, as counter‐ions. Reduction of these ions leads to metallic nanoparticles. In this way the brush layer attached to the surface of the particles becomes a “nanoreactor” that may be used for chemical conversions of the metal ions. We show that the reduction of AuClequation/tex2gif-stack-1.gif ions within these nanoreactors leads to well‐defined and rather monodisperse gold nanoparticles that are attached to the surface of the core. A stable dispersion of polymeric core particles with attached nanoparticles results. All results reported here suggest that chemical reactions of ions immobilized in spherical polyelectrolyte brushes provide a new route to composite particles of inorganic and organic materials.

Transmission electron micrograph of gold particles on a core‐shell system.     

无盐聚电解质溶液的分子热力学模型

聚电解质在水处理和胶体领域应用广泛 ,在生物系统中 ,蛋白质和 DNA等均是聚电解质 .文献中已发表了不少聚电解质溶液的理论和模型 ,如基于柱型胞腔模型的 Poison- Boltzmann( PB)方程理论[1]及其改进型 ( MPB) [2 ] 、Manning反离子凝聚理论 [3 ] 、积分方程理论 [4] 及适合于工程应用的半经验模型 [5 ]等 ,但离工程实际应用的要求还相差较远 .最近 ,姜建文等 [6]建立的分子热力学模型 ,其预测结果与 MD模拟数据非常吻合 .本文在此基础上进一步考虑聚离子与反离子间的缔合作用 ,可以在中高浓度范围内很好地关联实验数据 .1　模　　型…     

Photoprotolytic Reactions in Systems Immobilized on Silica Gel Using a Cationic Polyelectrolyte

Moscow University Chemistry Bulletin - The patterns of protolytic reactions in the immobilized state are studied using the example of classical systems with photoinduced proton transfer (2-naphthol...     

癸基硫酸钠和癸烷磺酸钠与阳离子聚电解质相互作用的差别

 通过表面张力及荧光探针方法, 研究了癸基硫酸钠和癸烷磺酸钠与阳离子聚电解质聚二甲基二烯丙基氯化铵(PDMDAAC)的相互作用. 结果表明, 虽然单一癸基硫酸钠和癸烷磺酸钠性质非常相似, 但它们与PDMDAAC的相互作用有明显差别, 癸基硫酸盐与PDMDAAC的相互作用明显强于癸烷磺酸盐. 通过量子化学计算结果对本文实验观测结果进行了解释.