Adsorption of codeine on hydrophilic silica and silica surface modified by hydrophobic groups in the presence of electrolytes

The adsorption of codeine from aqueous solution onto colloidal silica and silica surface-modified with chemiadsorbed octadecyl dimethyl silane (ODDMS) or dimethyl silane (DMS) groups was studied in the presence of neutral electrolytes at different pH values. From codeine-hydrochloride solutions codeine cations are strongly bound to negatively charged silica surfaces. Inorganic salts (NaCl, NaNO₃) reduce the adsorption of the organic cation. On silica modified by ODDMS (10% of surface silanol groups are occupied), codeine cations are adsorbed to a higher extent at pH 6, while at pH 8 the adsorbed amounts are lower than on the bare silica surface. Neutral electrolytes reduce codeine adsorption on the ODDMS modified silica. On the hydrophobic silica, completely covered by DMS groups, codeine adsorption is considerably lower than on the bare silica, but neutral salts increase the adsorption. The adsorption of codeine is compared with the adsorption of aggregating surfactant ions. Common and different features of their interactions with silica surfaces are outlined.     

表面活性离子液体参与构筑的胶束体系

离子液体的可设计性,使得新型表面活性离子液体不断涌现,从而将具有不同功能基团的离子液体引入到了传统的有序分子聚集体中,这也将有助于实现有序分子聚集体的可控性和功能化。本文综合评述了表面活性离子液体在水溶液及离子液体中的胶束化行为,重点总结了烷基碳链长度、阴离子结构和阳离子结构对表面活性离子液体聚集行为的影响,介绍了新型功能性表面活性离子液体在水溶液中的胶束化行为,分析了表面活性离子液体与传统表面活性剂复配体系的协同增效作用,并探讨了表面活性离子液体构建的胶束体系的发展方向。     

Grafting of silica during the processing of silica‐filled SBR: Comparison between length and content of the silane

The treatment of nanoscopic silica grafted in the blend during the processing of silica‐filled styrene butadiene rubber was performed with silane, introduced at different concentrations, or at a constant concentration with a given length of alkyl chain. From swelling measurements in water and in solvent, the maximum silane content that can be grafted has been calculated as a function of the length of the silane alkyl chains as well as their efficiency to cover the silica surface. The found values are close to the values found in the literature for grafting in solution. Moreover, a direct correspondence between the length of the silane alkyl chains and their concentration has been deduced. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 143–152, 2006     

Adsorption and adsolubilization of surfactants on titanium dioxides with functional groups

Adsorption of ionic surfactants on titanium dioxide with dodecyl chain groups or quaternary ammonium groups (XNm, where m is the carbon number of the alkyl chain, 4–16) was investigated. The adsorbed amount of cationic surfactants (dodecyltrimethylammonium bromide, DTAB; 1,2-bis(dodecyldimethylammonio)ethane dibromide, 2RenQ) on titanium dioxide with dodecyl chain groups increased with increasing concentration of the dodecyl chain due to hydrophobic interaction, where the adsorbed amounts of DTAB at saturation was considerably greater than those of 2RenQ. Adsorption of an anionic surfactant (sodium dodecyl sulfate, SDS) on XNm occurred mainly due to both electrostatic attraction force and hydrophobic interaction, depending on the alkyl chain length on XNm. On the other hand, adsorption of cationic surfactants, DTAC and 2RenQCl (their counter ions are chloride ions), on XNm was quite smaller compared with that of SDS due to electrostatic repulsion force. Adsolubilization of 2-naphthol in the surfactant-adsorbed layer on the titanium dioxides with the functional groups was also studied. The adsolubilized amounts of 2-naphthol on titanium dioxide with dodecyl chain groups were enhanced by adsorption of DTAB, but no distinct increase in the adsolubilization was observed by adsorption of 2RenQ. In the case of XNm, the amount of 2-naphthol adsorbed in the absence of surfactants increased with increasing alkyl chain length on XNm. Further, an appreciable increase in the adsolubilization of 2-naphthol on XNm with adsorption of 2RenQCl was observed. It was found from the admicellar partitioning coefficients that the adsolubilization of 2-naphthol preferably occurs on XNm by adsorption of SDS or 2RenQCl compared with that by DTAC. These differences in the adsolubilization were discussed by microproperties of the surfactant-adsorbed layers estimated using a spin probe.     

离子液体表面活性剂在水溶液中的自组装及其调控研究进展

离子液体表面活性剂在化学合成、材料制备和环境污染控制等方面的应用与它们在水溶液中的自组装及其微观结构密切相关。因此,研究离子液体表面活性剂在水溶液中的自组装行为具有重要的意义。本文重点综述了阳离子的结构、阴离子的类型、外加电解质、有机添加剂、环境因素(温度、溶液pH值和光)等对离子液体表面活性剂在水中的自组装行为以及对组装体结构影响的研究进展,总结了这些因素对离子液体表面活性剂在水中自组装的调控规律,展望了该领域的发展方向及面临的挑战。     

Preparation of silane-coated TiO2 nanoparticles in supercritical CO2

Nanometric inorganic pigments are widely used as fillers for hybrid composite materials. However, these nanometric powders are hydrophilic in nature and their surface must be functionalized before use. In this work, titanium dioxide (TiO₂) nanoparticles were coated using silane coupling agents with alkyl functionality. A supercritical carbon dioxide (scCO₂) method was used for surface silanization. Five alkylalkoxysilanes with different alkyl chain length and structure were studied: methyltrimethoxy, isobutyltriethoxy, octyltriethoxy, octyldimethylmethoxy and octadecyltrimethoxysilane. The microstructure and thermal stability of deposited monolayers were characterized using thermogravimetric analysis, ATR–IR spectroscopy, transmission electron microscopy, wettability characterization and low-temperature N₂ adsorption/desorption analysis. The use of scCO₂ as a solvent provided an effective approach to functionalize individual inorganic nanoparticles due to the enhanced diffusivity of the solution molecules in the aggregates interparticle voids. The trifunctional silanes employed here yielded surfaces with better thermal stabilities and greater hydrophobicities than the used monofunctional silane.     

Flow microcalorimetry of adsorption of anionic alkyl surfactants at the solid/liquid interface

Flow microcalorimetry was used to study the adsoption of anionic alkyl surfactants from aque--ous solutions onto silica. It is found that for alkyl sulfate systems the strength of adsorption interactionincreases with increases of the alkyl chain length and decreases as temperature rises. The adsorptiondepends only on monomer concentration of the solution even above the critical micelle concentration(cmc). The assumption is made that the adsorption involves only a transfer of monomers from bulkto surface phase. A different adsorption mechanism is operative for the alkyl carboxylate.     

Adsorption of Pyrimidine Nucleotides on a Titanium Dioxide Surface

The adsorption of pyrimidine mononucleotides from aqueous solutions on the surface of nanocrystalline titanium dioxide is studied. The interaction of the nucleotides with hydroxyl groups of titanium dioxide is interpreted in terms of the surface complexation theory. The results of an experimental study of the dependence of adsorption on the pH and ionic strength of solutions are used to calculate the stability constants of the outer-sphere adsorption complexes, which result from the electrostatic interaction of protonated groups with anionic forms of nucleotides.     

离子液体表面活性剂1-丁基-3-甲基咪唑烷基硫酸酯的合成及其在水溶液中的聚集行为

采用离子交换法,由1-丁基-3甲基咪唑氯盐（C4mimCl）和烷基硫酸钠合成了一系列无卤素的阴离子表面活性离子液体—1-丁基-3-甲基咪唑烷基硫酸酯[C4mim][CnH2n 1SO4](n=8,12,16),利用表面张力仪、稳态荧光光谱等手段考察了表面活性离子液体在水溶液表面及体相中的聚集行为,结果表明,与传统无机反离子相比,有机咪唑阳离子[C4mim] 作为反离子的离子液体型表面活性剂具有较高的表面活性,[C4mim] 产生的氢键引起的抑制分子规则排列的作用小于其促进分子有序排列的疏水作用。长烷基链的阴离子是界面膜及胶束的主要组成成分,阴离子疏水烷基碳链的增长虽然可促进胶束的形成,但却在一定程度上抑制[C4mim] 离子参与界面或胶束的形成;阴离子所带烷基链越长,越不利于阳离子[C4mim]＋参与界面膜或胶束的形成,界面膜或胶束中表面活性剂排布越松散,即界面张力越大,体系中胶束聚集数较小。     

TiO2在水及丙二醇介质中表面电性质的研究

0引言 固体颗粒在液相介质中的分散是基础研究领域和工业技术部门普遍遇到的问题 ?在化学工业领域,如涂料 ? 染料 ? 油墨 ? 化妆品等,固体颗粒的分散及分散稳定性直接影响着产品的质量和性能 ?TiO 2 颗粒的水基分散体系广泛应用于涂料 ? 油墨以及化妆品中,也是陶瓷制备过程中重     

The structure and adsorption properties of colloidal silica used in toothpastes

The dispersity, specific surface area, porosity, and pore size distribution are determined for samples of colloidal silica and calcium o-phosphate, toothpaste constituents. The results obtained show that adsorbents have the developed mesoporous structure. It was found that the adsorption of sodium lauryl sulfate and a nonionic surfactant, glyceryl monocaprylate, at the aqueous surfactant solution-colloidal silica interface is small and has the unusual character. The reasons for a low adsorption of surfactants and their mixtures on the surface of the studied adsorbents are discussed.     

Synthesis and Application of Hydride Silica Composites for Rapid and Facile Removal of Aqueous Mercury

The adsorption of ionic mercury(II) from aqueous solution on functionalized hydride silicon materials was investigated. The adsorbents were prepared by modification of mesoporous silica C‐120 with triethoxysilane or by converting alkoxysilane into siloxanes by reaction with acetic acid. Mercury adsorption isotherms at 20 °C are reported, and maximum mercury loadings were determined by Langmuir fitting. Adsorbents exhibited efficient and rapid removal of ionic mercury from aqueous solution, with a maximum mercury loading of approximately 0.22 and 0.43 mmol of Hg g^?1 of silica C‐120 and polyhedral oligomeric silsesquioxane (POSS) xerogel, respectively. Adsorption efficiency remained almost constant from pH 2.7 to 7. These inexpensive adsorbents exhibiting rapid assembly, low pH sensitivity, and high reactivity and capacity, are potential candidates as effective materials for mercury decontamination in natural waters and industrial effluents.     

Self-assembly of two- and three-dimensional particle arrays by manipulating the hydrophobicity of silica nanospheres

The surface hydrophobicity of colloidal silica (SiO2) nanospheres is manipulated by a chemical graft of alkyl chains with silane coupling agents or by physical adsorption of a cationic surfactant. The surface-modified SiO2 spheres can be transferred from the aqueous phase to organic solvents and readily self-assemble at the water-air interface to form two-dimensional (2D) particle arrays. Closely packed particle monolayers are obtained by adjusting the hydrophilic/hydrophobic balance of the synthesized SiO2 spheres and may further be transferred onto solid substrates layer by layer to form three-dimensional (3D) ordered particle arrays with a hexagonal close-packed (hcp) crystalline structure. The 2D monolayer and 3D multilayer SiO2 films exhibit photonic crystal properties, which were determined by the UV-visible spectroscopic analysis in transmission mode. In the multilayer films, the Bragg diffraction maxima increased with an increase in thickness of the particle layers. The experimentally observed diffraction positions are in good agreement with those that were theoretically calculated.     

Protecting nanoscaled non-oxidic particles from oxygen uptake by coating with nitrogen-containing surfactants

To suppress the reactivity of nanoscaled non-oxidic powders of titanium nitride (TiN) and silicon carbonitride (SiCN) against hydrolysis and oxidation, chemical surface modification with nitrogen-containing surfactants was investigated. Among these surfactants, long-chain primary amines, ethylenediamines, guanidines, nitriles, isocyanates, and succinimides were examined. Thermogravimetry, elemental analysis, and behavior against the water-vapor adsorption of the modified particles were used as methods to estimate the protective capacity of the organic coating material. The best results were obtained by using the long-chain amines and octadecylisocyanate, which were indicated by a significant shift of the powder oxidation toward the higher temperatures and an increase of the particle hydrophobicity. A long-chain succinimide was found to be the most effective in dispersing nanoscaled TiN in organic media. Preparation of a stable aqueous dispersion without significant changes in the elemental composition of the powder was achieved by the application of an ionic surfactant to the surface-modified particles.     

Adsorption of alkyl polyglucosides on the solid/water interface: equilibrium effects of alkyl chain length and head group polymerization

The equilibrium adsorption behavior of two n-alkyl-beta-D-glucosides (octyl (C8G1) and decyl (C10G1)) and four n-alkyl-beta-D-maltosides (octyl (C8G2), decyl (C10G2), dodecyl (C12G2), and tetradecyl (C14G2)) from aqueous solution on a titania surface, as measured by ellipsometry, has been investigated. The main focus has been on the effect of changes in the alkyl chain length and headgroup polymerization, but a comparison with their adsorption on the silica/water and air/water interfaces is also presented. Some comparison with the corresponding adsorption of ethylene oxide surfactants, in particular C10E6 and C12E6, is given as well. For all alkyl polyglucosides, the maximum adsorbed amount on titania is reached slightly below the critical micelle concentration (cmc), where it levels off to a plateau and the amount adsorbed corresponds roughly to a bilayer. However, there is no evidence that this is the actual conformation of the surfactant assemblies on the surface, but the surfactants could also be arranged in a micellar network. On hydrophilic silica, the adsorbed amount is a magnitude lower than on titania, corresponding roughly to a layer of surfactants lying flat on the surface. A change in the alkyl chain length does not result in any change in the plateau molar adsorbed amount at equilibrium; however, the isotherm slope for the alkyl maltosides increases with increasing chain length. Headgroup polymerization on the other hand affects the adsorbed amount. The alkyl glucosides start adsorbing at lower bulk concentrations than the maltosides and equilibrate at higher adsorbed amounts above the cmc. When compared with the ethylene oxide (EO) surfactants, it is confirmed that the EO surfactants hardly adsorb on titania, since the measured changes in the ellipsometric angles are within the noise level. They do, however, adsorb strongly on silica.     

Effect of surface coverage on the conformation and mobility of C18-modified silica gels

C18-modified silica gels with surface coverages of 2 to 8.2 micromol m(-2), were prepared by different synthetic pathways and characterized by Fourier Transform infrared spectroscopy (FTIR), solid-state nuclear magnetic resonance (NMR) spectroscopy, and chromatographic measurements. The effects of temperature and bonding density on the conformational order of C18-modified silica gels were studied in detail by FTIR spectroscopy. The silane functionality and degree of cross-linking of silane ligands on the silica surface were evaluated by 29Si cross-polarization magic-angle spinning (CP/MAS) NMR and the structural order and mobility of the alkyl chains were investigated by 13C CP/MAS NMR spectroscopy. CH2 symmetric and anti-symmetric stretching bands and CH2 wagging bands were used as IR probes to monitor the conformational order and flexibility of the alkyl chains in the C18 phases. Qualitative information about the conformational order was obtained from frequency shifts of the CH2 symmetric and anti-symmetric stretching bands. The relative amounts of kink/gauche-trans-gauche, double-gauche, and end-gauche conformers in the alkyl chains were determined by analysis of CH2 wagging bands. These results indicate that surface coverage plays a dominant role in the conformational order of C18-modified silica gels. The FTIR and NMR data are discussed in the context of the chromatographic shape-selectivity differences.     

Thin wetting films from aqueous solutions of surfactants and phospholipid dispersions

The microscopic thin wetting film method was used to study the stability of wetting films from aqueous solution of surfactants and phospholipid dispersions on a solid surface. In the case of tetradecyltrimethylammonium bromide (C(14)TAB) films the experimental data for the receding contact angle, film lifetime, surface potential at the vapor/solution and solution/silica interface were used to analyze the stability of the studied films. It is shown that with increasing C(14)TAB concentration charge reversal occurs at both (vapor/solution and solution/silica) interfaces, which affects the thin-film stability. The spontaneous rupture of the thin aqueous film was interpreted in terms of the earlier proposed heterocoagulation mechanism. The presence of the mixed cationic/anionic surfactants was found to lower contact angles and suppresses the thin aqueous film rupture, thus inducing longer film lifetime, as compared to the pure amine system. In the case of mixed surfactants hetero-coagulation could arise through the formation of ionic surfactant complexes. The influence of the melting phase-transition temperature T(c) of the dimyristoylphosphatiddylcholine (DMPC) on the stability of thin films from dispersions of DMPC small unilamellar vesicles on a silica surface was studied by measuring the film lifetime and the TPC expansion rate. The stability of thin wetting films formed from dispersions of DMPC small unilamellar vesicles was investigated by the microinterferometric method. The formation of wetting films from diluted dispersions of DMPC multilamellar vesicles was studied in the temperature range 25-32 degrees C. The stability of thin film of lipid vesicles was explained on the basis of hydrophobic interactions. The results obtained show that the stability of wetting films from aqueous solutions of single cationic and mixed cationic-anionic surfactants has electrostatic origin, whereas the stability of the phospholipid film is due to hydrophobic interaction.     

系列离子液体型Gemini咪唑表面活性剂在水溶液中的分子动力学模拟

利用分子动力学模拟方法研究了系列离子液体型Gemini咪唑表面活性剂在水溶液中的表面活性和胶束化能力. 模拟结果表明,压力张量法得到的表面张力模拟值偏小,需乘以修正系数矫正;分子动力学模拟得到的临界胶束浓度变化规律与实验相符,可以定性比较不同结构的离子液体型Gemini咪唑分子间的胶束化能力;温度的升高会加剧分子的热运动,不利于离子液体型Gemini咪唑表面活性剂在水溶液中形成胶束;此外,研究还发现联接基不同的离子液体型Gemini咪唑表面活性剂可能遵循不同的胶束化机理.S≤6时,单个分子自组装成胶球后发生聚合形成大胶团.随着咪唑上长烷烃链碳数的增加,[C_n-4-C_nim]胶束化能力提高;而随着联接链长度增加,[C₁₀-S-C₁₀im]胶束化能力降低;当S ＞6时,分子联接基弯曲并伸入其它分子烷烃链内部以减小头基分离力,从而形成稳定的胶束或胶团.随着联接基团亚甲基数的增加,头基斥力减小,附加疏水相互作用增强,[C₁₀-S-C₁₀im]胶束化能力提高.     

Fluorescence anisotropy in studies of solute interactions with covalently modified colloidal silica nanoparticles

Time-resolved anisotropy decays of a fluorescent cationic solute, rhodamine 6G (R6G), in Ludox sols were measured to characterize the extent of the ionic binding of the probe to silica particles after modification of the surface with neutral or cationic silane coupling agents. The anisotropy decays provided direct evidence for distribution of the dye between the aqueous solution (picosecond decay component) and silica particles (nanosecond decay component and residual anisotropy component, which were attributed to the wobbling motion of dye on the silica surface and to the ionically bound probe, respectively). The dye was strongly adsorbed to unmodified silica nanoparticles, to the extent that less than 1% of the dye was present in the surrounding aqueous solution. Significant decreases in the degree of probe adsorption were obtained upon covalent modification of the silica with neutral or cationic silanes, with up to 80% of the probe being present in the aqueous solution in cases where the surface was coated with (3-aminopropyl)triethoxysilane. The addition of such agents also altered the fractional distribution between the nanosecond decay component and the residual anisotropy component in favor of the nanosecond component, indicative of weaker interactions between the dye and the modified surface (i.e., more wobbling motion). The data clearly show the power of time-resolved fluorescence anisotropy decay measurements for probing the modification of silica surfaces and should prove useful in characterization of new chromatographic stationary phases.     

CMC型高分子表面活性剂在固/液界面上的吸附

在润湿、乳化、洗涤、分散等应用领域中,表面活性剂分子在界面上的吸附状态对性能有重要影响.另一方面,在化学驱油过程中,表面活性剂分子在氧化物矿物上的吸附是引起表面活性剂损失的主要原因,表面活性剂的损耗量大,将降低采收率及经济效益[1].高分子表面活性剂作为一种多功能的新型表面活性剂在许多领域有广阔的应用前景,但对其性能研究尚处于起步阶段,特别是结构复杂的高分子双亲性共聚物,在吸附、乳化等方面研究尚少报导.羧甲基纤维素系列高分子表面活性剂是采用独特的超声波辐照技术合成的嵌段型共聚物,具有优良的表/界面活性[2],可望用…