The effect of ionisation of silica nanoparticles on their binding to nonionic surfactants in oil–water system: an atomistic molecular dynamic study

ABSTRACT

In this study, the adsorption of nonionic surfactant, triethylene glycol monododecyl ether (C₁₂E₃), on a surface of silica nanoparticle (NP) has been studied with variation in the degree of ionisation (DI) of silica NP using all-atom molecular dynamic simulations in hexadecane–water system. Hydrogen bonding is found to be responsible for the adsorption of C₁₂E₃ on NP, particularly at low DI. We observe that with increasing DI of NP, the amount of adsorption of C₁₂E₃ on NP reduces, which is negligible beyond DI ～ 0.5. The decrease in the adsorption with increasing DI is due to the decrease in the number of hydrogen bonds formed by the silica NP with surfactant molecules. Potential of mean force (PMF) profiles indicate attractive interactions between NP and C₁₂E₃ for DI < 0.5, and for larger DI depletion effect is observed. This work explains the unusual effect of nonionic surfactant on interfacial tension in the presence of silica particles as observed in recent experiments.     

Lower critical solution temperature (LCST) and theta temperature of aqueous solutions of nonionic surface active agents of various polyoxyethylene chain lengths

Cloud points of aqueous solutions of homogeneous poly(oxyethylene)dodecyl ether derivatives (C₁₂(OE)_n: n=2–8) and the apparent theta temperatureT ^ap were determined from the abrupt changes in optical transmittance and the temperature dependence of the second virial coefficient obtained by light scattering measurements. It was found that the lower critical solution temperature (LCST) shifts to a lower temperature and lower concentration as the number of oxyethylene units in a molecule decreases. Because of this behavior of LCST, the modified Flory-Schultz plot of phase separation was applied to the present nonionic surfactant-water system, and its theta temperature obtained. The dependence ofT ^ap on the number of oxyethylene units suggests that the polyoxyethylene chain has different effects on the solubility of C₁₂(OE)_n in water forn less than or equal to 3 from those forn greater than or equal to 4.     

表面活性剂Tween对TS-1合成及催化性能影响的研究

以添加吐温的少量四丙基氢氧化铵（TPAOH）为模板剂,水热下合成了钛硅分子筛（TS-1）。采用FTIR、XRD、SEM、BET、UV-Vis等手段对分子筛进行表征。XRD结果表明,所得样品完全晶化,具有典型的MFI拓扑学结构;FTIR结果表明,样品在960 cm－1处出现了强吸收峰,表明钛已进入骨架;UV-Vis谱图表明,所合成样品在330 nm附近没有电子跃迁信号,表明其中没有锐钛矿型TiO2;SEM结果表明所合成样品的晶粒大小均匀。在添加适量吐温所得的胶团溶液中,模板剂分子与吐温之间的协同作用有助于TPAOH与硅、钛源定向反应,避免非骨架TiO2的生成,减少了TPAOH的用量,丙烯环氧化反应结果表明,吐温20、吐温40、吐温60及吐温80等非离子表面活性剂的添加都有助于降低模板剂（TPAOH）的用量和提高TS-1的催化活性,其中吐温40的影响尤为显著,吐温40/TPAOH摩尔比为0.02时,过氧化氢转化率达98.1%,环氧丙烷选择性和收率分别可达96.1％和94.3％。     

非离子乳化剂对淀粉接枝丙烯酰胺、丙烯酸反相乳液聚合反应的作用

接枝共聚;非离子乳化剂对淀粉接枝丙烯酰胺、丙烯酸反相乳液聚合反应的作用     

The synthesis of trimeric comb-type nonionic surfactants and their application in microemulsion flushing fluid

In order to effectively remove the oil-based drilling that remains on the wall of a well and improve the quality of well cementation, flushing fluid must be used to clean it. Due to its excellent flushing effect, microemulsion flushing fluid has been a hot area of research in recent years; the application, however, is limited because of its poor resistance to temperature. In this paper, for the purpose of enhancing the temperature resistance of microemulsion flushing fluid, a new type of comb-shaped trimeric nonionic surfactants N,N-bis(2-stearamidoethyl) stearamide was synthesized, and an anionic–nonionic surfactants composite oil-in-water microemulsion flushing fluid (ANC-MEFF in short) to flush the oil-based drilling was formed. Studies have shown that it has a good flushing effect on oil-based drilling between 20 and 160°C, and its flushing efficiency can reach 93% or even higher. Compared with the CW210L organic phosphorus flushing fluid (Number 1 in short), the flushing efficiency increased by about 20?~?40%, while the microemulsion flushing fluid formed by OP-10 (Number 2 in short) increased by 30% in high temperature, with the application temperature ranging from 20?~?60 to 20?~?160°C, respectively. Additionally, it was found that the microemulsion flushing fluid can make the borehole wall and casing wall change from “oil-wet” into “water-wet”, which is conducive to promoting the quality of cementation between the first and second interfaces intuitively.     

铜电极上Zn—Co—P合金电沉积行为

铜电极上Ｚｎ┐Ｃｏ┐Ｐ合金电沉积行为黄清安＊陈永言邓伯华（武汉大学化学系武汉４３００７２）关键词铜电极，Ｚｎ－Ｃｏ－Ｐ合金，电沉积１９９６－０４－２３收稿，１９９６－０９－１３修回国家自然科学基金资助课题为了提高Ｚｎ层的耐蚀性，出现了含磷的锌基合金，...     

A moving-boundary technique for the measurement of diffusion in liquids. triton X-100 in water

A modified taylor dispersion technique is used to measure liquid-phase mutual diffusion coefficients D. Rather than inject a narrow band of solution of solute concentration C+C into a carrier stream of composition C, the carrier stream is switched from a solution of composition C-(C/2) to a solution of composition C+(C/2), forming an initially-sharp moving boundary at the tube inlet. D is calculated from the refractive index profile across the broadened boundary at the tube outlet. Since the mean of concentration of the diffusing solute (C) is constant throughout the run, the calculated value of D accurately represents the differential value at C, even if relatively large concentration differences are used or if D is sensitive to composition. The advantages of the technique are illustrated by measuring the diffusion of aqueous Triton X-100, a nonionic surfactant. D is found to drop sharply as the concentration is raised through the critical micelle concentration near 0.15 g-L^–1.     

金属纳米粒子/聚合物体系的稳定性及其机理

金属纳米粒子由于其小的尺寸和大的比表面积等特点,使其具有独特的热性能、电性能、磁性能和光性能,以及很强的团聚趋势。因此金属纳米粒子是否被稳定在纳米尺度内,是它们能否表现出独特性能的关键。本文综述了非离子聚合物、聚电解质、两亲聚合物、双亲水聚合物、树状聚合物对金属纳米粒子的稳定作用及其稳定机理的研究进展。     

Gelled emulsions with a high water content

The structure of a gel containing 99% water, 0.5% of a nonionic surfactant and 0.5% of a hydrocarbon was investigated by analysis of its equilibrium phases and their state of dispersion by liquid helium freeze fracture electron microscopy.The gel consisted of aqueous droplets of micron size separated by a thin membrane of a lamellar liquid crystal and a W/O microemulsion with droplets varying between 200 and 1000 Å in diameter.     

The Micellar Dissociation Concentration of Polyoxyethylene Mono N-Decylether Nonionic Surfactants in Water

This paper will demonstrate a method for determining the micellar dissociation concentration (MDC) of polyoxyethylene mono n-decylether nonionic surfactants in water. Turbidity and surface tension measurements were applied to commercial samples without further purification. Complicated curves containing turbidity maxima and surface tension minima were obtained for some impure samples. It is difficult to determine the critical micellar concentration (CMC) for impure surfactants. Explanations are given for all curves obtained for pure and impure samples and the method of identifying the MDC values is illustrated. It is more practical for surfactant users to determine the MDC values in their own laboratory than to search for the CMC values in the literature when the surfactants arc impure.