甲酰胺,乙酰胺,尿素在两种极性非水溶液中的体积性质

以尿素、甲酰胺和乙酰胺为溶质，二甲基甲酰胺和二甲基亚砜为溶剂；或以二甲基甲酰胺、二甲基亚砜为溶质，以甲酰胺为溶剂，通过测定溶液在２９８．１５Ｋ下的密度数据，求得了溶质的表观磨尔体积以及与溶质－溶质相互作用相关的体积第二维里系数。利用定标粒子理论讨论了溶质分子的几何体积、溶质－溶剂相互作用对溶质偏摩尔体积的影响，结果表明，熔质的溶剂化与溶质－溶质相互作用的体积效应呈相反的变化趋势。     

甲酰胺、乙酰胺、尿素在两种极性非水溶剂中的体积性质

以尿素、甲酰胺和乙酰胺为溶质,二甲基甲酰胺和二甲基亚砜为溶剂;或以二甲基甲酰胺、二甲基亚砜为溶质,以甲酰胺为溶剂,通过测定溶液在２９８．１５Ｋ下的密度数据,求得了溶质的表观摩尔体积以及与溶质－溶质相互作用相关的体积第二维里系数．利用定标粒子理论讨论了溶质分子的几何体积、溶质－溶剂相互作用对溶质偏摩尔体积的影响,结果表明,溶质的溶剂化与溶质－溶质相互作用的体积效应呈相反的变化趋势     

关于溶解性的几个问题

讨论了溶质和溶剂的极性与溶解度的关系;分子所含的极性基团与溶解度的关系;同素异形体和同分异构体的溶解性;在同一溶剂中2种溶质对溶解性的相互影响;溶质在混合溶剂中的溶解性;两亲（亲水、亲脂）溶质的溶解性;金属间的相互溶解。     

多环芳烃水中溶解度的理论计算

建立了计算多环芳烃水中溶解度的数学表达式，用量子化学方法计算了7个多环芳烃的水中溶解度，计算结果与实验测定结果相符合．多环芳烃处于水体内体系状态能量愈高，其溶解度愈小，多环芳烃中的碳氢基团越多，溶解度越小．此时体系中的溶质呈单分子态，而不是聚集态．     

糖与非电解质在甲酰胺中相互作用的Gibbs自由能参数

用气液色谱法测定了298.15K时10个非电解质溶质在不同浓度甲酰胺糖(葡萄糖,果糖,蔗糖)溶液中的保留参数.依据McMillanMayer理论,求得非电解质溶质与糖间的Gibbs自由能相互作用参数g_ij和g_ijj.采用OkamotoWood的基团加合法,求得各基团的Gibbs自由能相互作用参数G_x,y,讨论了非电解质溶质与糖间的相互作用以及溶剂性质的影响.     

超临界CO2-溶质二元系的密度及溶质的偏摩尔体积

在308．15和318．15K温度下，80－170bar压力范围内，测定了CO2-乙醇、CO2-丙酮和CO2-正庚烷混合物的密度，溶质的浓度范围是0－1．3mol·L－1．在此基础上，计算了溶质的偏摩尔体积，系统地研究了温度、压力和溶质浓度对二元混合物密度的影响，并从压力和溶质浓度对溶质偏摩尔体积影响的角度研究体系中的分子间相互作用．     

逆流溶质出峰顺序的预测

 根据逆流保留方程可知,溶质的出峰顺序主要取决于其在互不混溶的两液相间分配系数的大小顺序。以饱和及不饱和脂肪酸乙酯、2,4 二硝基苯胺基脂肪醇和对硝基苯基葡萄糖甙等结构较为简单、极性差别较大的溶质系列为研究对象,应用修正的通用基团活度系数(UNIFAC)(Dortmund)模型,通过相平衡计算,预测了它们在含水或不含水的溶剂体系中分配系数的变化趋势,并与前人的工作进行了对比。结果表明,由该方法预测出的相似结构溶质分配系数的顺序基本上与实验值相同,其中对饱和脂肪酸乙酯在己烷 乙腈(体积比为1∶1)体系中分配系数的预测最好。     

溶解过程的体积效应

溶质微粒与溶剂微粒间相互作用导致溶解,因相互作用溶解常伴随着体积效应。若质-剂微粒间作用和原先溶质微粒间、溶剂微粒间作用相近,如C6H6和C6H5CH3互溶,溶液体积常是溶质体积和溶剂体积之和;多数情况下,质-剂间作用较强,所以,V液相似文献   

反相毛细管电色谱中溶质保留值与溶剂化结构参数间的定量关系

利用线性溶剂化能关系（ＬＳＥＲ）方法，研究了反相毛细管电色谱（ＲＰ－ＣＥＣ）中溶质保留值与溶剂化结构参数间的定量关系。发现决定溶质在ＲＰ－ＣＥＣ中保留行为的主要因素为溶质的体积及溶质作为氢键受体的碱性大小；建立了溶质在ＲＰ－ＣＥＣ中的ｌｏｇｋ′以及保留方程ｌｏｇｋ′＝ｌｏｇｋ′ｗ－Ｓφ中ｌｏｇｋ′ｗ，Ｓ与溶质的溶剂化结构参数间的定量关系；此外，还建立了不同流动相体系间溶质的ｌｏｇｋ′ｗ和Ｓ值的换算方程。     

N2,O2水溶液光谱的分子动力学模拟

用分子动力学模拟方法研究了N2和O2水溶液的光谱性质．给出了能描述分子内部运动的溶质－溶剂相互作用势．对溶质和溶剂原子的速度自相关函数（VACF）作了计算．讨论了所得VACF的性质并计算了其谱密度．溶质分子振动谱出现的红移，与液态N2，O2的Raman实验结果相吻合．模拟得出的转动谱表明了溶剂分子对溶质转动运动的阻滞，模拟结果也表明VACF计算对溶液和液体光谱的研究十分有效．     

A small-angle X-ray scattering study of the interactions in concentrated silica colloidal dispersions

The structure factors of colloidal silica dispersions at rather high volume fractions (from 0.055 to 0.22) were measured by small-angle X-ray scattering and fitted with both the equivalent hard-sphere potential model (EHS) and the Hayter-Penfold/Yukawa potential model (HPY). Both of these models described the interactions in these dispersions successfully, and the results were in reasonable agreement. The strength and range of the interaction potentials decreased with increasing particle volume fractions, which suggests shrinkage of the electrical double layer arising from an increase in the counterion concentration in the bulk solution. However, the interactions at the average interparticle separation increased as the volume fraction increased. The interaction ranges (delta) determined by the two models were very similar. Structure factors were also used to determine the size and volume fraction of the particles. The values of the size obtained from the structure factors were slightly larger than those obtained from the form factors; this difference is ascribed to the nonspherical shape and polydispersity of the colloidal particles. The volume fractions measured by these two methods were very similar and are both in good agreement with the independently measured results.     

硫化铜纳米粒子的多种制备方法

纳米粒子制备方法的研究在整个纳米技术领域占有十分重要的地位。目前,虽然纳米粒子的制备方法很多［1~7］,但合成工艺简单、成本低廉、易于工业化的合成技术还不多,限制了纳米材料奇特而广泛的应用前景。 纳米材料的功能不但取决于其化学组成,而且取决于纳米粒子的形态和物理组成。例如二氧化钛粒子粒径为2000nm时,对可见光的散射率最大,遮盖力最强,广泛用于高档油漆、油墨颜料,而粒径减小至 10~60nm时,则具有透明性、强紫外线吸收能力,可用于高档化妆品、透明涂料等[8] 。此外,形状不同亦将影响纳米粒子的性能,如磁记录粒子a-…     

Analyte solvent and injection volume as variables affecting method development in semipreparative reversed-phase liquid chromatography

Analyte solvent and injection volume were examined as parameters that affect peak elution during method development for semipreparative RP HPLC purification. Analytical and semipreparative scale HPLC with gradient elution were used to analyze a mixture of three standard compounds with significantly different retention factors (k). This mixture was analyzed after (i) dissolution in solvents of varied compositions, and (ii) with progressively larger injection volumes. As analyte solvent composition and injection volume were changed, the most notable effects on peak shape were observed for the compounds with the smallest k values. Overall changes in peak shape were less pronounced when analyte solvent composition was similar to the starting mobile phase regardless of injection volume. Scale-up to semipreparative conditions yielded results consistent with those observed at the analytical scale. These data show that peak shape is greatly affected by analyte solvent composition and injection volume, and that these effects can be ameliorated by the dissolution of analytes in solvent that closely resembles that of the mobile phase used for initial run conditions. The following study addresses the concepts of peak elution in RP HPLC and how they factor into semipreparative purification.     

Molecular Dimension and Interaction Parameters of Polyacrylamide in Water‐N,N‐Dimethylformamide Mixtures

The intrinsic viscosities [η] of polyacrylamide (PAM) having different average molecular weights are measured in various mixtures of water (good solvent) and N, N dimethyl formamide (DMF, nonsolvent) at different temperatures. The observed results show a significant variation of cosolvency as a function of solvent composition (?_DMF). The nature of curves in [η] vs. ?_DMF plot at different temperatures indicates the existence of two antagonistic effects. The unperturbed dimensions (K_θ) of the polymer are determined by a number of methods, which agree well with each other. The temperature coefficient of unperturbed dimension (K′), molecular extension factors (α_n), characteristic ratio (C_α) and chain rigidity (σ) are evaluated and the effects of temperature, solvent composition are discussed. The volume related parameter V_E and shape factor ν were also computed, which shows the shape of polymer molecules to be more or less spherical in solution.     

Induced detachment of coalescing droplets on superhydrophobic surfaces

Coalescence of a falling droplet with a stationary sessile droplet on a superhydrophobic surface is investigated by a combined experimental and numerical study. In the experiments, the droplet diameter, the impact velocity, and the distance between the impacting droplets were controlled. The evolution of surface shape during the coalescence of two droplets on the superhydrophobic surface is captured using high speed imaging and compared with numerical results. A two-phase volume of fluid (VOF) method is used to determine the dynamics of droplet coalescence, shape evaluation, and contact line movement. The spread length of two coalesced droplets along their original center is also predicted by the model and compared well with the experimental results. The effect of different parameters such as impact velocity, center to center distance, and droplet size on contact time and restitution coefficient are studied and compared to the experimental results. Finally, the wetting and the self-cleaning properties of superhydrophobic surfaces have been investigated. It has been found that impinging water drops with very small amount of kinetic impact energy were able to thoroughly clean these surfaces.     

Determination of volumetric shrinkage of thermally cured thermosets using video-imaging

Video-imaging is one method of analyzing the shrinkage of resins. For the measurement, a drop of resin is placed near an illumination source and its contour is imaged from the front with a camera. This paper presents a further development, detailed investigation and verification of this technique to analyze the chemical shrinkage of thermally cured epoxy resins during cure. A new cylindrical sample holder was developed which enables the automated detection of the baseline, as well as defining the scale within the pictures. In a test series, the resin's volume was varied, as well as its contour. The findings confirm that the measured volume shrinkage is independent of the drop shape.Finally, the obtained shrinkage results were verified and evaluated in comparison with values measured by a mercury dilatometer and a rheometer. The shrinkage results of the investigated new method are in good accordance with the more established methods.     

Limiting conditions for applying the spherical section assumption in contact angle estimation

The shape of liquid drops on solid surfaces deviates from the spherical as tension decreases and gravity effects start affecting the drop shape. This paper attempts to define this deviation and estimates the dimensionless Eotvos number limits above which the deviation becomes "significant." The use of these limiting values can facilitate estimation of contact angle in the following manner. It is well known that the equilibrium contact angle made by a liquid drop on a solid surface can be estimated from measurements of two drop parameters. These parameters can be any two chosen from the drop volume, height, and wetted radius. In case the effect of gravity on the drop shape is negligible, simple algebraic relations derived from the spherical section assumption exist, from which the contact angle can be estimated. In systems where the "spherical section" assumption is invalid, the Laplace equation for the drop shape has been solved numerically with any two of the above parameters as the constraints, to obtain the contact angle. In this paper, Eotvos numbers at which the deviation of the drop profile from the spherical is significant enough to result in contact angle deviation of 1 degrees are estimated. The limiting values of Eotvos number, expressed as a function of the original contact angle made by the spherical profile, are obtained by solving the Laplace equation for the drop shape with the drop volume and wetted radius constraints for decreasing values of Interfacial tension. These limiting values are also estimated for different drop sizes and for cases where the drop phase is heavier (sessile) and lighter (buoyant) than the surrounding fluid. The independence of the Eotvos number estimates from the sign of the density difference as well as the drop size is shown. These Eotvos number limits can be used to check if the spherical section assumption, with the resulting simple algebraic relations, can be used for contact angle estimation and other shape-related analysis for a system.     

Temperature-induced phase transition in hydrogels of interpenetrating networks poly(N-isopropylmethacrylamide)/poly(N-isopropylacrylamide)

The combination of ¹H NMR spectroscopy, DSC, dynamic mechanical spectroscopy, and optical microscopy was used to investigate temperature-induced volume phase transition in hydrogels of interpenetrating networks (IPNs) poly(N-isopropylmethacrylamide)/poly(N-isopropylacrylamide) (PNIPMAm/PNIPAm) with various PNIPMAm content. In these IPNs, both networks are thermosensitive; such systems were not examined so far. All methods showed phase transition starting at 307 K, which is the volume phase transition temperature of PNIPAm, the major network component. Only the sample with the lowest content of PNIPAm (~54 %) shows two-step collapse transition, other samples with higher PNIPAm content show a single transition in NMR and DSC which indicates enhanced mutual entanglement of both components. In all samples, the phase transition results in substantial increase of both components of the shear modulus. Although the properties of all samples change with temperature in similar way, differences in dependence on the PNIPMAm content and the shape of the sample can be seen.     

General methods for free-volume theory

Free-volume theory for understanding depletion phenomena in mixtures of two species is generally derived using scaled-particle theory for those specific entities. Here we first give a general scaled-particle method for convex bodies in terms of the characteristic geometrical measures of the depletion agent, i.e., its volume, surface area, and integrated mean curvature, in mixtures with hard spheres. Second, we show that similar results can be derived from fundamental-measure theory. This different approach allows us to get a deep insight into the meaning of the various contributions to the theory from a geometrical point of view. From these two methods we arrive at a generalized "recipe" to free-volume theory. This recipe can be based on a desired equation of state for any convex shape of the depletion agents and is also valid for (polydisperse) mixtures of those. This is illustrated by mixtures of spheres with ellipsoids, spheres with several geometries as models for disklike mesogens, e.g., gibbsite, as well as depletion of spheres due to bar-shaped colloids, e.g., goethite.