The electrocapillarity of polyacrylates

Summary The electrocapillary properties of polyacrylic acid have been studied by two methods. Exploratory measurements have been made of the effect of the polymer on the differential capacity of a mercury drop in 0.1 m sodium perchlorate. They showed that the polymer was strongly adsorbed over a wide range of potentials but that it did not appear to form a monolayer. The surface excess of polymer obtained from drop weight data showed a maximum at very low concentrations and then a decline at higher concentrations. The bulk of the work was carried out by making surface tension measurements, using a sessile mercury drop, in solutions of a fraction of polyacrylic acid (mol. wt. 7.02×10⁴) in potassium chloride at 0.01, 0.1, 0.2, and 0.5 m at 25°C.The data have been used to evaluate the surface excesses of the polymer and of the inorganic ions. The distribution of K⁺ and Cl^– in the electrical double layer and the contact adsorption of Cl^– on the mercury were very little affected by the presence of the polymer. The surface excess of polymer was always found to be greatest at low concentrations, to decrease steeply at first as the concentration was increased and then to decrease more slowly at higher concentrations.Possible explanations of this behaviour are discussed and it is concluded that the rapid decrease is a consequence of molecular weight dispersion and the stronger adsorption of high molecular weight polymer. The slow decrease in surface excess at higher concentrations may be a result of configurational changes of the polymer molecules.Surface pressure data show that, despite this decrease in the surface excess, the surface coverage reaches a high level at very low polymer concentrations and then continues to increase slowly as the concentration of polymer is increased. This apparent contradiction is due to changes in configuration of the adsorbed polymer molecules. At higher bulk concentrations the chain configurations are more compact and each adsorbed molecule makes more contacts with and so occupies a greater area of the mercury surface than at low concentrations.The conclusion is reached that the surface excess of polymer is mostly contained in a layer probably more than 1000 Å thick. It consists of a concentrated and entangled mass of polymer chains. Relatively few of these chains are in contact with the mercury at any istant. The concentration in this surface layer decreases steadily with increasing distance from the mercury surface and it merges without discontinuity into the bulk solution.With 10 figures in 22 details     

裂解色谱法研究PMR型聚酰亚胺前体的反应过程

用裂解气相色谱法研究ＰＭＲ型聚酰亚胺前体在反应中的化学变化过程，以裂解产物醇和环戊二烯的生成率表示酰胺化或酰亚胺化及交联的程度，结果表明，酰胺化或酰亚胺化在５０℃以下不发生，在１８０～２２０℃完成，降冰片烯端基在１５０℃以下不发生交联反应，在２８０℃，１０～１８小时可完成交联反应。     

Synthesis and crystal structure of a new one-dimensional system with end-to-end single dicyanamide bridges between nickel(II) centres

The complex [Ni(tn)₂{N(CN)₂}]ClO₄ (tn=trimethylenediamine) has been synthesized and the structure has been determined. The complex forms a one-dimensional chain structure via the bidentate bridging ligand dicyanamide. A two-dimensional networks is formed via interchain hydrogen bond interactions.     

聚砜-尼龙6嵌段共聚物结构的研究

<正> 以金属钠作催化剂合成的聚砜-尼龙6嵌段共聚物对尼龙6的吸水性有一定的改善,而且可以作为聚砜与尼龙共混物的相容剂,但共聚物中聚砜组分的含量都不超过25％。这可能与共聚物的结构有关。近年来的工作表明:反相气相色谱法(IGC)是高聚物结构分析的有用的工具之一。我们试图用反相气相色谱法,通过观察嵌段共聚物     

A spectroscopic study on the 12-heteropolyacids of molybdenum and tungsten (H3PMo12−nWnO40) combined with cetylpyridinium bromide in the epoxidation of cyclopentene

The epoxidation of cyclopentene with hydrogen peroxide catalyzed by 12-heteropolyacids of molybdenum and tungsten (H₃PMo_12−nW_nO₄₀, n = 1–11), 12-tungstophosphoric acid and 12-molybdophosphoric acid combined with cetylpyridinium bromide as a phase transfer reagent was carried out in acetonitrile. Among 13 heteropolyacids investigated, catalyst of H₃PMo₆W₆O₄₀ showed the highest activity, giving a conversion of 60% and a selectivity of 95% in the epoxidation of cyclopentene. The fresh catalysts and the catalysts under reaction condition were characterized by UV–vis, FT-IR and ³¹P NMR spectroscopy, which has revealed that all of the molybdotungstophosphoric acids were degraded in the presence of hydrogen peroxide to form a considerable amount of phosphorus-containing species. The active species resulted from H₃PMo₆W₆O₄₀ are new kinds of phosphorus-containing species, which is different from {PO₄[WO(O₂)₂]₄}³⁻.     

Controlled growth of large-area, uniform, vertically aligned arrays of alpha-Fe2O3 nanobelts and nanowires

Vertically aligned iron oxide nanobelt and nanowire arrays have been synthesized on a large-area surface by direct thermal oxidation of iron substrates under the flow of O(2). The effects of reactive gas pressure, composition, and temperature have been systematically studied. It was found that nanobelts (width, tens of nanometers; thickness, a few nanometers) are produced in the low-temperature region (approximately 700 degrees C) whereas cylindrical nanowires tens of nanometers thick are formed at relatively higher temperatures (approximately 800 degrees C). Both nanobelts and nanowires are mostly bicrystallites with a length of tens of micrometers which grow uniquely along the [110] direction. The growth habits of the nanobelts and nanowires in the two temperature regions indicate the role of growth rate anisotropy and surface energy in dictating the ultimate nanomorphologies.     

锌试剂分光光度法测定壳聚糖含量

利用锌试剂与壳聚糖在一定酸度条件下的特异性显色反应，即其复合物在465nm处吸光度与壳聚糖含量在0～O．04g／L范围内呈现良好的线性关系(R=0．996)，基于此建立了一种简便快速的分光光度法。平均回收率为99．68％。     

杯芳烃的配位化学──Ⅳ.对叔丁基杯[8]芳烃与钙、镉配合物的合成与表征

本文合成了对叔丁基杯[8]芳烃(H₈L)与钙、镉的固体配合物。并以元素分析、核磁共振、热谱、红外谱、紫外谱等进行表征。其配合物的组成分别为Ca(H₆L)·6dmf及Cd(H₆L)·6dmf.