PVP和SDS在固液界面上的混合吸附

实验测定了PVP和SDS自其混合溶液在碳黑及TiO₂表面上的吸附。在TiO₂表面上,当溶液中SDS的浓度低于4×10^-3mol·dm^-2时,PVP与SDS的吸附互相增强;当SDS的浓度更高时,则彼此对抗。在碳黑表面上,SDS与PVP表现为单纯的竞争吸附。根据SDS与PVP之间复合物的形成和吸附剂的表面性质讨论了实验结果。     

AgI溶胶界面移动法电泳实验聚沉现象分析

本文通过对AgI溶胶电泳时产生聚沉的原因进行分析,指出伴随电泳而发生的电极反应产物有可能成为破坏溶胶稳定性的主要因素.     

巯基聚乙二醇5000修饰的金溶胶的稳定性: 从DLVO稳定到空间稳定

研究了α-甲氧基-ω-巯基聚乙二醇(mPEG-SH, 5000 MW)修饰的金溶胶的稳定性, 初步探讨了其稳定机制. 将线性mPEG-SH通过巯基化学吸附于金溶胶表面, 可形成高分子层包被的金溶胶. 研究结果表明, PEG修饰的金溶胶可以在pH＝1～13.5或盐浓度高达1.20 mol/L的较苛性条件下保持稳定. 这是由于金溶胶表面吸附的高分子保护层为溶胶提供了新的空间稳定, 取代了溶胶原来的DLVO稳定(实质是电荷稳定). 因而, PEG保护的金溶胶在很大程度上克服了DLVO稳定的溶胶对环境敏感、易聚沉的缺点, 能在复杂的条件(如生理条件)下应用. 鉴于PEG的水溶性、无毒性和生物亲和性, 这种具有较高稳定能力的金纳米粒子/PEG复合体结合了金纳米粒子和PEG的优异性能, 可作为生物纳米探针用于复杂条件下的生物分析.     

配体保护下的Au_(20)团簇吸附和活化CO的理论研究

用密度泛函理论方法计算了CO分子吸附在有机配体聚乙烯吡咯烷酮poly(N-vinyl-2-pyrrolidone)(PVP)保护下的Au20团簇上的稳定构型的结构和性质。配体PVP通过物理吸附主要作用于Au20团簇的顶点位置。与Au20比较,配体的存在有利于CO的吸附和活化,其根本原因是PVP和CO在Au20表面分别作为供电子和吸电子基团产生的协同效应。中性及阴离子Au20团簇对配体和CO的吸附强度不同,前者对PVP吸附作用较强,后者对CO的吸附和活化作用较强。     

不同水环境对纳米银颗粒聚集体粒径大小及界面电势的影响

研究了不同水环境对无稳定剂与PVP为稳定剂的纳米银颗粒的物化性能的影响。结果表明:随着电解质浓度的增加,纳米银颗粒的粒径与界面电势逐步增大;二价阳离子比一价阳离子更能有效地使纳米银粒径与界面电势增加;稳定剂PVP,腐植酸及其他天然有机物能够增加纳米银溶胶的稳定性;在天然水体中,纳米银在海水中的粒径颗粒与界面电势比湖水中更大。     

聚乙烯吡啶树脂对间苯二酚的吸附性能研究

通过悬浮聚合法,合成了一种聚乙烯吡啶树脂(PVP)。以大孔弱碱树脂D301和大孔吸附树脂XAD-4作为参照,研究了PVP树脂对间苯二酚的吸附性能,探讨了溶液的p H值及无机盐对树脂吸附间苯二酚的影响。结果表明,溶液pH值为6.02时,PVP树脂对间苯二酚的吸附量达到134mg/g,无机盐对PVP吸附间苯二酚几乎无影响。Freundlich等温吸附方程能够很好地拟合PVP树脂吸附间苯二酚的等温线,且间苯二酚在PVP树脂上的吸附为放热过程,能够自发进行。     

PVP 稳定的纳米 Au 溶胶对葡萄糖液相选择氧化的催化性能

 采用化学还原法制备了聚乙烯吡咯烷酮 (PVP) 稳定的纳米 Au 溶胶, 这种 Au 溶胶在葡萄糖空气氧化制葡萄糖酸反应中具有良好的催化性能. 考察了 PVP 加入量和氯金酸前驱液的浓度对反应活性的影响. 紫外-可见吸收光谱和透射电镜分析结果表明, 含有较小 Au 粒子的 Au 溶胶体系具有较高的催化活性. 当 PVP/Au 质量比为 40, 氯金酸浓度为100 μg/ml 时, 得到稳定的 Au 溶胶体系具有金粒子尺寸小、分布均匀的特点, 对葡萄糖氧化反应活性高, 葡萄糖的转化率达到 54.4%.     

一种具有Z-Scheme机制的高效可见光驱动的介孔AgI@Fe-MIL-88B-NH_2光催化剂（英文）

以磺化聚苯乙烯微球为模板制备了具有开口结构的介孔Fe-MIL-88B-NH_2球壳,据此进一步通过原位反应法合成一种新型具有可见光活性的AgI改性Fe-MIL-88B-NH_2微球。与纯的AgI和Fe-MIL-88B-NH_2相比,制备的AgI@Fe-MIL-88B-NH_2复合材料的光催化活性显著提高,这是由于吸附能力和电荷分离均得到增强的缘故。电荷分离机制可归因于形成了不含氧化还原调节剂的直接Z-Scheme系统,该系统使光生电子从Fe-MIL-88B-NH_2的导带迁移至AgI的价带上,从而产生活性更强的·O2-和·OH。     

PVP改性氧化硅溶胶的微结构和流变性

以正硅酸乙酯为前驱体,聚乙烯吡咯烷酮（PVP）为聚合物改性添加剂,在碱性条件下制备氧化硅溶胶,通过小角X射线散射测量了改性溶胶的微结构参数,辅以动态光散射观测溶胶颗粒生长,研究了聚合物量、碱催化剂量和水量对溶胶颗粒度、分形特征以及流变性的影响规律.由于PVP链中强极性的分子内酰胺基团和氧化硅颗粒表面的羟基形成氢键,致使溶胶颗粒被聚合物链包裹,严重阻碍了溶胶颗粒的生长,使凝胶时间延长,流变性发生变化,同时对溶胶颗粒的微结构产生影响.     

聚乙烯吡啶树脂对富马酸的吸附性能研究

通过静态吸附实验,研究了聚乙烯吡啶树脂(PVP)对富马酸的吸附性能。结果表明,该树脂对富马酸的吸附等温线同时满足Langmuir和Freundlich等温吸附方程;在无机盐存在下,与大孔强碱性树脂D204、弱碱树脂D308相比,PVP吸附富马酸的性能几乎不受无机盐的影响。D204树脂吸附富马酸是离子交换作用,D308树脂通过Lewis作用和静电作用吸附富马酸,而PVP树脂对富马酸的吸附行为是氢键所致,吸附为放热过程且能够自发进行。     

Synthesis and characterization of polymer-protected rhodium and palladium sols in mixed media

A series of polymer-protected rhodium and palladium sols were generated in mixed (organic/aqueous) dispersion media. Protecting polymers used were PAA, PVP, PVA and an oligosaccharide-based protecting agent, arabinogalactan. This is the first systematic study of colloids generated in mixed solvent dispersion media with these protecting agents. The sols were characterized by TEM, UV/Vis spectrophotometry and Photon Correlation Spectroscopy (PCS). In general, the macroscopic stability of the sols depended on the protecting agent/organic cosolvent combination used, with a nonlinear dependence on cosolvent concentration. Observed sol stabilities correlated well with pre-existing hydrodynamic data for the protective polymers, e.g. radius of gyration data. Average particle size and polydispersity of all sols examined decreased as cosolvent concentration increased, with actual cosolvent concentration, protecting agent and reducing agent used influencing the extent of decrease. Sol particle sizes ranged from 0.8 nm to 6.0 nm with sol turbidities decreasing in parallel with the particle sizes. Hydrodynamic sizes (from PCS) tended to reflect the sols' macroscopic stabilities. FTIR studies using adsorbed CO as a spectroscopic surface probe indicated decreases in the ν(CO)(ads) stretching frequency with an increase in cosolvent concentration due to competitive adsorption of CO with the cosolvent molecules on the metal colloid surfaces.     

Interfacial and bulk behavior of sodium dodecyl sulfate in isopropanol-water and in isopropanol-poly(vinylpyrrolidone)-water media

The surface activity of isopropanol (IP) and poly(vinylpyrrolidone) (PVP) at the air/water interface has been studied. The self-aggregation of sodium dodecyl sulfate (SDS) in IP-water as well as in IP-PVP-water media has been investigated using physical methods, viz., tensiometry, conductometry, calorimetry, and viscometry. The interaction of SDS with PVP in IP-water medium as well as its self-aggregation (or micellization) in the presence of PVP has been assessed. The results reveal a fair degree of surface activity of IP in aqueous medium, which is only moderate for PVP. The critical micellar concentration (CMC) of SDS passes through a minimum at (v/v) % IP = 6.62. SDS interacts with PVP, yielding a critical aggregation concentration (CAC) at a low [SDS], independent of IP content in the medium. At a higher [SDS], free micelle formation takes place in solution, which is lower in mixed solvent than in water and is independent of solvent composition by tensiometry, but not by conductometry and calorimetry. The viscosity of micelle-interacted PVP in solution takes a long time to stabilize, whereas, for non-interacting additives, such as NaCl and cetyltrimethylammonium bromide (CTAB), it is time independent.     

The Effect of Macromolecules on Foam Stability in Sodium Dodecyl Sulfate/Cetylpyridinium Bromide Mixtures

Abstract

The effects of macromolecules, gelatin, and polyvinylpyrrolidone (PVP), on the properties of foam comprising sodium dodecyl sulfate (SDS) and cetylpyridinium bromide (CPDB) have been studied by measurements of foamability, foam stability, surface tension, and solution specific viscosity. The results indicate that foamability and foam stability are significantly improved when macromolecules are added into mixed systems. Both gelatin and PVP associate with SDS/CPDB surfactants and form aggregates. Electrostatic repulsion and steric stabilization between the two sides of the foam lamellae, due to aggregation, and prevention of drainage in the lamellae, achieved by the long chains of macromolecules are the reasons for increasing foamability and foam stability. The interactions between PVP and surfactants is weaker than those between gelatin and surfactants. The strongest association between macromolecules and surfactants occurs when the molar ratio of SDS/CPDB is 1:1. By comparing PVP with gelatin, the former is favored to increase foamability, and the latter is favored to increase foam stability.     

Adsorption of non-ionic and cationic polymers on silica from their mixed aqueous solutions

The adsorption of polyvinylpyrrolidone (PVP) and poly(dimethyldiallylammonium chloride) (PDC) on silica from their mixed aqueous solutions has been investigated as a function of PVP concentration in the presence of PDC. The adsorption of PVP is almost unchanged with the feed concentration of PVP, while the adsorption of PDC decreases with increasing PVP concentration, especially at high concentrations of PDC. The conformation of PVP in the adsorbed layer on silica is relatively flat at low concentrations of PDC, but is extended in solution at high concentrations of PDC. The stability of the silica dispersion is low and the ζ potential is relatively small at low concentrations of PDC, whereas a stable dispersion is obtained at high concentrations of PDC and the ζ potential is large. Thus the stability of the dispersion is well correlated with the electrostatic repulsion and steric repulsion forces operating at the particles.     

Effect of ethanol on the interaction between poly(vinylpyrrolidone) and sodium dodecyl sulfate

The effect of ethanol on the interaction between the anionic surfactant sodium dodecyl sulfate (SDS) and the nonionic polymer poly(vinylpyrrolidone) (PVP) has been investigated using a range of techniques including surface tension, fluorescence, electron paramagnetic resonance (EPR), small-angle neutron scattering (SANS), and viscosity. Surface tension and fluorescence studies show that the critical micelle concentration (cmc) of the surfactant decreases to a minimum value around 15 wt % ethanol; that is, it follows the cosurfactant effect. However, in the presence of PVP, the onset of the interaction, denoted cmc(1), between the surfactant and the polymer is considerably less dependent on ethanol concentration. The saturation point, cmc(2), however, reflects the behavior of the cmc in that it decreases upon addition of ethanol. This results in a decrease in the amount of surfactant bound to the polymer [C(bound) = cmc(2) - cmc] at saturation. The viscosity of simple PVP solutions depends on ethanol concentration, but since SANS studies show that ethanol has no effect on the polymer conformation, the changes observed in the viscosity reflect the viscosity of the background solvent. There are significant increases in bulk viscosity when the surfactant is added, and these have been correlated with the polymer conformation extracted from an analysis of the SANS data and with the amount of polymer adsorbed at the micelle surface. Competition between ethanol and PVP to occupy the surfactant headgroup region exists; at low ethanol concentration, the PVP displaces the ethanol and the PVP/SDS complex resembles that formed in the absence of the ethanol. At higher ethanol contents, the polymer does not bind to the ethanol-rich micelle surface.     

Influence of polyvinylpyrrolidone (PVP) on alumina sols prepared by a modified Yoldas procedure

Al₁₃ polycations containing alumina sols, prepared by a modified Yoldas procedure were mixed with polyvinylpyrrolidone (PVP). Although Al speciation in freshly prepared sols was not affected by PVP addition the decay rate of Al₁₃ polycations was slightly decreased in PVP-containing sols. PVP does not show any influence on particle size and particle growth. The influence of PVP addition on viscosity and flow behavior of modified Yoldas sols depends on their solids content and molar ratio.     

Morphological change of the micelle of poly(styrene)-b-poly(2-vinylpyridine)-b-poly(ethylene oxide) induced by binding of sodium dodecyl sulfate

Morphological change of a micelle of poly(styrene)-b-poly(2-vinylpyridine)-b-poly(ethylene oxide) (PS-PVP-PEO) polymer was induced by binding sodium dodecyl sulfate (SDS) to the PVP block in acidic aqueous solutions. The change in the size of SDS/PS-PVP-PEO complexes was detected by dynamic light scattering measurements and atomic force microscopy, and the binding of SDS was confirmed by zeta-potential measurements. When the micelle was free from SDS in acidic aqueous solutions, the hydrodynamic diameter of the micelle was 216 nm, reflecting the extended conformation of the PVP block due to the repulsion between protonated pyridine units. As the cationic PVP block was electrically neutralized with anionic SDS, the diameter was gradually reduced concomitant with the decrease in zeta-potential and finally reached 175 nm when the PVP block was completely neutralized. The decrease in the diameter shows the morphological change of the PVP block from extended to shrunken forms. Further addition of SDS did not cause the changes of the diameter nor zeta-potential. This indicates that SDS was not bound to the PS-PVP-PEO polymer after the PVP block was fully neutralized and that the hydrophobic binding of SDS to the polymer was negligible due to the low concentration of SDS.     

The stability of lyophobic and lyophilic sols

The problem of the nature of the stability of colloidal solutions and the mechanism of their coagulation by electrolytes has been examined. On the basis of an analysis of a general criterion for the stability of ionstabilized disperse systems and a comparison of the theoretical results with the experimental facts, it has been concluded that the actual coagulation process in lyophobic sols never takes place by a purely concentration mechanism. Neutralization effects, associated with adsorption phenomena, which take place in a colloidal system when electrolytes are added, are of considerable importance. When treated with nonionogenic surface-active substances, hydrophobic sols are converted into hydrophilic sols, which retain their stability even in moderately concentrated electrolyte solutions. This conversion is brought about as a result of the adsorption of molecules of the surface-active compounds, leading to the production of hydrophilic properties on the surface of the colloidal particles. It has been suggested that the coagulation of these lyophilic sols takes place as a result of the breakdown of the polymolecular solvate layers at the boundary of the colloidal-disperse phase.Paper read at the XX International Congress of Pure and Applied Chemistry, Moscow, July, 1965.     

Nanoparticle formation of poorly water-soluble drugs from ternary ground mixtures with PVP and SDS

Poorly water-soluble drugs N-5159, griseofulvin (GFV), glibenclamide (GBM) and nifedipine (NFP) were ground in a dry process with polyvinylpyrrolidone (PVP) and sodium dodecyl sulfate (SDS). Different crystallinity behavior of each drug during grinding was shown in the ternary Drug/PVP/SDS system. However, when each ternary Drug/PVP/SDS ground mixture was added to distilled water, crystalline nanoparticles which were 200 nm or less in size were formed and had excellent stability. Zeta potential measurement suggested that the nanoparticles had a structure where SDS was adsorbed onto the particles that were formed by the adsorption of PVP on the surface of drug crystals. Stable existence of crystalline nanoparticles was attributable to the inhibition of aggregation caused by the adsorption of PVP and SDS on the surface of drug crystals. Furthermore, the electrostatic repulsion due to the negative charge of SDS on a shell of nanoparticles could be assumed to contribute to the stable dispersion.