Mixed micellization of an anionic gemini surfactant (GA) with conventional polyethoxylated nonionic surfactants in brine solution at pH 5 and 298 K

The micellization behavior of an anionic gemini surfactant, GA with nonionic surfactants C₁₂E₈ and C₁₂E₅ in presence of 0.1 M NaCl at 298 K temperature, has been studied tensiometrically in pure and mixed states, and the related physicochemical parameters (cmc, γ _cmc, pC ₂₀, Γ _max, and A _min) have been evaluated. Tensiometric profile (γ vs log [surfactant]), for conventional surfactants, generally consists of a single point of intersection; a gradually decreasing line (normally linear, or with slight curvature) ultimately saturates in γ at a particular [surfactant], corresponding to complete monolayer saturation. The gemini, in this report, led to two unequivocal breaks in the tensiometric isotherm. An attempt to the interpretation of the two breaks from molecular point of view is provided, depending solely on the chemical structure of the surfactant. The gemini, even in mixed state with the conventional nonionic surfactants C₁₂E₅ and C₁₂E₈, manifested the dual breaks; of course, the dominance of the feature decreases with increasing mole fraction of the nonionics in the mixture. Theories of Clint, Rosen, Rubingh, Motomura, Georgiev, Maeda, and Nagarajan have been used to determine the interaction between surfactants at the interface and micellar state of aggregation, the composition of the aggregates, the theoretical cmc in pure and mixed states, and the structural parameters according to Tanford and Israelachvili. Several thermodynamic parameters have also been predicted from those theories.     

金属材料分析方法的选择和施行：第五讲 金属材料中钨的测定（续）

此外,尚有二硫酚、邻羟基酚类试剂、酸性三苯甲烷类试剂、偶氮类试剂以及荧光酮类试剂等也都有应用于钨的光度测定的实例。但由于共存元素的干扰以及方法的成熟程度等问题尚未完全得到解决,在金属材料分析中的应用尚不普遍。其中,苯基荧光酮类试剂对钢铁中低含量钨的测定有一定的应用前景,举两例说明:例1:邻氯苯基荧光酮(o-Cl-PF)-CTMAB光度法测定钢及合金中低含量钨[w(W)0.01%~0·50%]。称取试样0.100 0~0.200 0 g,溶于硫酸-磷酸混合酸(H2SO4+H3PO4+H2O=3+10+12)10 mL中,滴加浓硝酸约1 mL氧化,蒸发至冒白烟,冷却,加水溶解盐类后冷…     

Study on synthesis of two-armed polymers containing a crown ether core and their self-assembly behaviors in selective solvents

A series of well-defined two-armed polymers containing a crown ether core, poly(stearyl methacrylate)-crown ether-poly(stearyl methacrylate) (PSMA-crown-PSMA), with different molecular weight were synthesized via atom transfer radical polymerization (ATRP). The resultant polymers were characterized by ¹H NMR and GPC. The self-assembly behaviors of this kind of polymer in selective solvents were studied by TEM, and it was found that polymers with different molecular weight can directly self-assemble into hollow spheres, solid spheres and a monolayer film with regular pores by varying molecular weight and water content. The possible molecular packing motels for their self-assembly behaviors were proposed.     

A remarkable stereoselectivity switching upon solid-state versus solution-phase enantiodifferentiating photocyclodimerization of 2-anthracenecarboxylic acid mediated by native and 3,6-anhydro-γ-cyclodextrins

The enantiodifferentiating [4+4] photocyclodimerization of anthracenecarboxylic acid (AC) mediated by native, mono- and di-3,6-anhydro-γ-cyclodextrins was investigated in both aqueous solution and solid-state. The solid-state photolyses gave inherently disfavored head-to-head photodimers in much higher chemical and optical yields than in the aqueous solution.     

Surface Modification of Fine Particles with a SnO<Subscript>2</Subscript> Film by Using a Polyhedral-Barrel Sputtering System

Fine particles were modified with a thin film of SnO₂ by using a barrel sputtering system that is a dry process. The conditions for the preparation of SnO₂ were studied by reactive sputtering onto a glass plate substrate. The optimal conditions for the preparation of tetragonal SnO₂ were identified as 60% partial oxygen pressure and 1.0 Pa total gas pressure with the substrate at room temperature. Under the optimized conditions, the surfaces of Al flake particles were modified with a thin film of SnO₂. XRD and SEM/EDS analysis of the prepared samples showed that the Al particle surfaces were uniformly modified by a thin film of SnO₂ in all cases. The film thicknesses were 80, 130, and 180 nm at RF outputs of 195, 350, and 490 W. These measured thicknesses coincided with the values estimated from the interference colors of the samples.     

从头计算方法比较TiSi_2的C54相和C49相

采用平面波超软赝势描述多电子体系,利用密度泛函理论和广义梯度近似,计算出C54相和C49相TiSi2的晶格常数、体弹性模量、形成能、电子态密度(DOS)和Mulliken电荷布居等性质.通过比较这两种物质的性质,发现尽管两者形成能很相近,但C49相结构对称性差、体弹性模量小、熔点低,Ti原子d轨道的反键强、离子性弱.这些性质上的差异和C49相TiSi2在固相反应中优先形成有关.     

A Large Conformational Change of a Bridged β-Cyclodextrin Dimer in Aqueous Solution

A novel bridged β-CD dimer in which two β-cyclodextrins were linked by a naphthalene at positions 2 and 7 has been synthesized. 1H and 13CNMR measurements showed that a large change in the conformation of the dimer occurred in aqueous solution. The dimer interacted with methyl and ethyl orange to form stable inclusion complexes via "induced fit" mechanism.     

大环二萜天然产物(±)-Mayol的全合成

西松烷型二萜类化合物是一大类广泛分布于松脂、烟草、陆地动物及海洋生物体中的具有十四元碳环骨架的化合物.其结构新颖复杂,且大多具有显著和广谱的生物活性.近几十年来,有关这类化合物的研究已引起了人们的极大兴趣.因此,开展这类天然产物及其类似物的全合成及构效关系的研究不仅具有重要的学术价值,而且具有潜在的应用前景.     

二(β-二酮)氧钒(Ⅳ)与含氮碱加合物的合成和表征

合成了一系列VO(β-dik)_2L类型加合物,其中β-dik分别为苯甲酰丙酮,2-噻吩甲酰三氟丙酮,L3-甲基吡啶、4-甲基吡啶、吗啉、异喹啉,VO(bza)_2Mor、VO(tta)_2Mor、VO(tta)_2iso-q为首次合成,并通过元素分析、摩尔电导、红外光谱、电子光谱、顺磁共振波谱等对加合物进行了较系统的表征工作。     

介质对配合物稳定性的影响——Ⅱ.Cu(SCN)+—NaNO3—二氧六环—水体系

本文用分光光度法确定了25℃时配阳离子Cu(SCN)~+在NaNO_3—二氧六环—H_2O介质中的稳定常数。溶剂组成变化范围为0,5,10,15和20wt％二氧六环,离子强度范围为0.2～3.0moledm~(-3),溶液的pH=1.5～1.6。本文提出了基于Pitzer方程式的最小二乘多项式逼近法,确定出各种不同组成混合溶剂中配合物的热力学稳定常数。讨论了该常数和一级介质效应与溶剂组成和介电常数的关系。