红外光谱研究硬脂酸单分子膜与十八胺单分子膜之间的相互作用

研究了硬脂酸单分子膜和十八胺单分子膜两者间的相互作用.为了观察它们之间是否发生酸碱反应,分别把硬脂酸和十八胺的氯仿溶液滴加到气液界面上,形成两类物质的单分子膜区域.然后把这两种单分子膜在水气界面上混合.通过红外光谱研究表明:质子在两类单分子膜之间是很难转移的,同时红外光谱证明由硬脂酸单分子膜和十八胺单分子膜制备的混合LB膜主要由独立的硬脂酸区域和十八胺区域组成.     

On the Predominant Electron-Donicity of Polar Solid Surfaces

The reasons for the predominant electron-donicity of almost all solid polar surfaces and its implications are discussed in this paper. By contact angle or interfacial tension measurements, the electron-accepting as well as the electron-donating properties of polar liquids can be ascertained, through the interplay between their energies of adhesion and cohesion. For the solid-liquid interface, direct interfacial tension measurements are not possible, but indirectly, solid/liquid interfacial tensions of polar systems can be obtained by contact angle measurement. However, as the energy of cohesion of a solid does not influence the contact angle formed by a liquid drop placed upon its surface, one can only measure the solid surface'ks residual polar property, manifested by the energy of adhesion between solid and liquid. This residual polar property is of necessity the dominant component; in most cases this turns out to be its electron donicity. When, by means of contact angle measurements with polar liquids, both electron-accepting and electron-donating potentials are found on a polar solid, it is most likely still partly covered with a polar liquid: usually water. The amount of residual water of hydration of a polar solid follows from its polar (Lewis acid-base) surface tension component (γ^AB). The degree of orientation of the residual water of hydration on a polar solid can be expressed by the ratio of the electron-donating to electron-accepting potentials (γ^⊖/γ^⊕), measured on the hydrated surface.     

酸碱理论在现代有机反应的应用

酸碱理论是一个重要无机化学理论,在无机化学中有着重要的作用,同时在有机化学中也有着广泛的应用。本文简单介绍了现代酸碱理论的发展,简单概述了几个在有机化学中常用的酸碱理论:酸碱质子理论、酸碱电子子理论、软硬酸碱理论。同时简要讲述酸碱质子理论、酸碱电子子理论在有机反应中的应用,以及在某些有机合成方面的应用实例。     

Electrochemistry as a Tool to Monitor Lewis Acid-Base Reactions between Methacrylonitrile and Metallic Surfaces: A Theoretical and Experimental Proposal

This paper presents a tentative extension of the Lewis acid-base concept to the case of an organic molecule interacting with a polarized metallic surface. Towards this aim, we make use of the Density Functional Theory (DFT) viewpoint on Lewis acid-base interactions. This theory has been shown to be relevant to describe adhesion processes at a molecular scale. It allows the introduction of three key parameters, for the molecule as well as for the metallic surface. These are the DFT chemical potential, μ, the absolute hardness, η and the Fukui function, f(inag hear). In the present paper, we show that the DFT chemical potential, μ, of the metallic surface is linearly related to the electrode potential drop, Δε, imposed between this surface and a reference electrode in an electrochemical cell. Thus, while the chemical potential of the molecule is only determined by its chemical structure, that of the metallic surface can be monitored continuously. This means that the Lewis acidic or basic character of the metallic surface towards the molecule can, in principle, be chosen. We present experimental results arguing in the sense of this model by studying the interaction of 2-methyl 2-propenenitrile (methacrylonitrile) alternatively with a metallic cathode and with a metallic anode. The two different transient molecule surface interactions are frozen thanks to an anionic electropolymerization of the monomer on the cathode and to a (first reported) cationic electropolymerization of the monomer on the anode. A detailed analysis of the molecular structures of the two resulting polymer/metal interfaces shows results which are in agreement with the theoretical predictions.

This paper is dedicated to Professor Jacques Schultz as an acknowledgement of his constant interest in our work.     

Bond Characteristics at Pigment-Polymer Interfaces

An assessment was made of the effectiveness of bonding polymers from solution to dispersed solids by dispersive and non-dispersive forces. The polymers included neutral low density polyethylene (LDPE), a basic ethylene co-vinyl acetate (EVA) and an acidic chlorinated polyethylene (CPE). The solids included surface coated rutiles, an organic colorant and the chromatographic support Chromosorb.^® The quality of polymer-solids bonds was estimated by eluting adsorbed polymers with p-xylene under reflux. The amount of polymer recovered was a function of acid-base forces acting at the polymer-solid interface. LDPE was recovered quantitatively, as were EVA and CPE when these were adsorbed on like (acid or base) solids but recovery was limited when significant acid-base interaction occurred. These results were relevant to the stabilization of solids dispersed in polymer solutions. Sedimentation experiments noted that the absence of acid-base interactions as well as an excess of these non-dispersive forces was detrimental to the stability of dispersions. For the specific systems under study, however, it was possible to define a preferred, intermediate range of acid-base interactions for dispersion stability. The configuration of adsorbed polymer chains was suggested to be an important consideration in this regard.     

Equilibrium approaches to natural water systems—6. Acid-base properties of a concentrated bog-water and its complexation reactions with aluminium(III)

A filtered bog-water, concentrated by means of a freezing technique, has been studied with respect to acid-base properties and aluminium(III) complexation reactions. Sampling was performed during autumn and winter periods with a resulting acidity or alkalinity due to oxic (autumn) or anoxic (winter) conditions. The measurements were performed as potentiometric titrations in constant ionic media (0.02, 0.1 and 0.6 M NaCl) with the use of a glass electrode. The samples show buffer ranges at 3 pH 5 and pH 7.5. The first is ascribed to the presence of carboxylate groups and is characterized by fast equilibria. The second is due to phenolic OH⁻ groups and precipitation reactions with resulting sluggish equilibria. For one sampling period comprehensive measurements were undertaken to study the possible polyelectrolytic character of the organic acids. Due to the small increase in apparent carboxylate pKa-values with the degree of dissociation at low (0.02 M) as well as at high (0.6 M) ionic strength, the possible polyelectrolytic feature of the acids was neglected. Instead, a good fit to data was obtained by introducing a di-protic acid (H₂L) as a model compound. Furthermore the medium dependence of the two acidity constants could satisfactorily be fitted to the expression:

Full-size image (1K)

, where K is the constant at infinite dilution, a and b parameters of which b has been adjusted to present data. The following K values were obtained: pK₁ = 3.65 and pK₂ = 4.30. The complexation with Al(III) could be described by the formation of AlL⁺, AlL₂⁻ and the ternary species AlLH₋₁. The stability constants (log k₁ = 4.4 (winter), 4.2 (autumn); log k₂ = 4.2, 4.7; pKa (AlL⁺) = 4.2, 4.2) show no significant trend with sampling period but indicate a stability of the complexes greater than for phtalic acid but lower than for oxalic acid. Finally, the theoretical solubility of the clay mineral kaolinite in the presence of bog-water was computer modelled. The calculations show up on a 10-fold increase with respect to soluble aluminium at pH = 5.     

高温燃烧中和法测定玻璃中硫溶解度的研究

提出了一种测定玻璃中S溶解度的方法高温燃烧中和法,它简便实用、重现性好、成本低、易于实施。本文采用高温燃烧中和法,研究了样品量、助剂的比例、测试温度、测试时间等因素对玻璃中硫溶解度测定结果的影响,得到最佳测定条件：以氧气作载气、WO3作助剂,样品量为0.3g、助剂的比例为1：1、测试温度为1400℃时,测试时间为20min.     

Sulfonated poly(propylene oxide) oligomers/Nafion acid-base blend membranes for DMFC

A novel functional poly(propylene oxide)-backboned diamine of M_w 400 (abbreviated as D400) was grafted with sulfonic acid (abbreviated as D400-PS) to improve the performance of Nafion^® membranes in direct methanol fuel cells (DMFCs). The interaction of the D400-PS with Nafion^® was studied by Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC). The performance of the blend Nafion^®/D400-PS membranes was evaluated in terms of methanol permeability, proton conductivity and cell performance. The proton conductivity of the blend membrane was slightly reduced by rendering proton conductivity to D400 by functionalized with an organic sulfonic acid. The methanol permeability of the blend membrane decreased with increasing of D400-PS content. The methanol permeability of the blend Nafion^®/D400-PS with the composition 3/1 (–SO₃H/–NH₂) was 1.02 × 10⁻⁶ cm² S⁻¹, which was reduced 50% compared to that of pristine Nafion^®. The current densities that were measured with Nafion^®/D400-PS blend membranes in the ratio 1/0 and 5/1 (–SO₃H/–NH₂), were 51 and 72 mA cm⁻², respectively, at a potential of 0.2 V. Consequently, the blend Nafion^®/D400-PS membranes critically improved the single-cell performance of DMFC.     

汽爆酸碱耦合解聚玉米秸秆分子结构的研究

以玉米秸秆为研究对象,采用蒸汽爆破+5％ H2 SO4和蒸汽爆破+5％ NaOH的耦合方法对其结构进行解聚处理,并对解聚前后秸秆的结构、化学组成、热稳定性能进行分析和表征.结果表明:与未处理前相比,经蒸汽爆破+碱解聚处理后,秸秆中大部分半纤维素被脱除,半纤维素由29.10％最低可降至4.61％,木质素由38.12％最低可降至10.74％.经蒸汽爆破酸耦合和蒸汽爆破碱耦合解聚处理后,纤维素含量由31.54％分别提高到65.16％和80.41％,秸秆最大失重率为81.86％和89.31％,最低吸热量为87.48 J/g和114.79 J/g,降解温度达到350℃,热稳定性能增加,表面结构疏松,出现小孔和裂缝.说明蒸汽爆破酸耦合和蒸汽爆破碱耦合解聚方法对玉米秸秆分子结构有一定的解聚效果.但就脱除半纤维素效果而言,蒸汽爆破碱耦合法优于蒸汽爆破酸耦合法.     

泥煤表面的酸碱性质

采用非连续酸碱滴定法探讨了泥煤表面酸碱性质,根据实验所得数据运用Origin7.0软件程序对泥煤表面的质子化和去质子化过程相关参数进行多元非线性拟合,计算表明,泥煤表面可交换位点密度Nt=5.06×10-3mol/g,质子化常数pK1=1.67和pK2=7.28,为进一步研究有害阳离子与泥煤之间的表面作用机制提供了重要参数.泥煤表面质子电荷随pH值变化而变化.