DTAB降低饱和烷烃与水的界面张力的研究

判断一种表面活性剂降低油-水界面张力性能的优劣,就需要对界面张力进行准确有效的测量。文章就不同浓度的十二烷基三甲基溴化铵(DTAB)水溶液分别与正庚烷(n-Heptane)和正十六烷(n-Hexadecane)之间的界面张力进行定量的测量,分别得到了在30℃下水-正庚烷和水-正十六烷体系的界面张力随DTAB浓度变化的曲线。结果表明,在DTAB浓度达到其所在体系中的CMC值时,水-正庚烷体系界面张力小于水-十六烷体系界面张力。DTAB具有较强的抗矿盐能力,界面张力随温度升高有所下降。     

正十六烷基磺酰氯的合成

正十六烷醇经亚磺酰甩作用转换成1－氯代正十六烷,在相转移催化剂条件下,1－氯代正十六烷和硫脲进行亲核反应,合成正十六烷基异硫脲盐酸盐,并以此为中间体用氯气氧化法制备正十六烷基磺酰氯,纯度大于95％,总收率为67％。     

溴化十六烷基三甲铵+正十六烷混合单分子层在空气-水界面上的二维相变化

用椭圆偏振光仪测定了不同温度时由溴化十六烷基三甲铵和正十六烷抅成的混合单分子层在空气-水界面上的椭圆率系数,证明该混合单分子层在髙于正十六烷正常熔点6℃的温度时有一从凝聚相到扩展液相的二维相变化.对椭圆率系数进行了理论预测,预测结果与实验值吻合良好.     

不同取代位置的萘衍生两亲分子在气/液界面组装膜中的螺旋结构与圆偏振发光

Langmuir-Blodgett(LB)技术可在二维气/液界面上精确地控制分子之间的排列及堆积方式, 构建有序超薄膜及纳米组装体. 同时, 界面这一不对称环境也可有效放大组装体的手性信息, 实现超分子体系中的手性传递和手性放大. 本文研究了萘环取代位置不同的两种手性两亲分子——N,N′-双十八烷基-α-萘-L-氨基-谷氨酸二酰胺(1NLG)和N,N′-双十八烷基-β-萘-L-氨基-谷氨酸二酰胺(2NLG)在气/液界面的铺展及组装行为, 发现同分异构效应影响了两亲分子在界面的排列, 1NLG组装形成了均一的纳米带状结构, 而2NLG则形成了左手螺旋结构, 并且2NLG薄膜表现出圆偏振发光(CPL)性质, 其不对称因子(g_lum)比三维体相组装体(超分子凝胶)大23倍, 表明界面促进了超分子手性的放大.     

通过溴代烷烃和羧基的酯化反应制备烷基改性的多壁碳纳米管

以1,8-二氮-二环[5,4,0]-7-十一烯(1,8-Diazabicyclo[5,4,0]undec-7-ene, DBU)作为催化剂, 通过溴代烷烃和羧基的酯化反应制备了烷基改性的碳纳米管. 分别采用1,6-二溴己烷、溴代正辛烷、溴代正十二烷和溴代正十六烷与硝酸氧化处理的碳纳米管反应, 在碳纳米管表面共价接枝了不同长度的烷基链. 实验结果表明, 烷基改性的碳纳米管能够很好地分散在二氯甲烷、氯仿等有机溶剂中; 并且随着接枝的烷基链碳数的增加, 碳纳米管在有机溶剂中的分散性也越好.     

全氟及α,α-二氯多氟烷基亚磺酸盐的反应

全氟烷基亚磺酸钠与溴水反应,得到全氟烷基磺酰溴(RfSO2Br),(但在乙腈,乙酸等有机溶剂中与溴反应,则生成溴代全氟烷.在碘化钾水溶液中,全氟烷基亚磺酸钠与碘反应,生成碘代全氟烷.α,α-二氯多币烷基亚磺酸钠在类似条件下与溴水反应,生成1-溴-1,1-二氯多氟烷,与碘在磺化钾水溶液中反应,生成1-碘-1,1-二氯多氟烷.1-溴-1,1-二氯多烷及1-碘-1,1-二氯多氟烷易对烯键加成,也可与连二亚硫酸钠在温和条件下发生亚磺化脱溴及脱碘反应.α,α-二氯二氟乙基亚磺酸钠在强酸中比较稳定,与强碱,氧化剂或还原剂发生反应,得到相应的产物.     

环己烷存在下环糊精诱导a-溴代萘室温燐光

微量环己烷存在下,β-环糊精能诱导α-溴代萘发射强的室温燐光.发光光谱、燐光寿命和荧光偏振的实验证实了β-环糊精一环已烷一α-溴代萘三元包络物的形成.测定了三元包络物的表观形成常数,讨论了环已烷对β-环糊精诱导α-溴代萘室温燐光的影响机制.     

聚合型表面活性剂用作分析试剂-PPOTA与PPOCA的合成及分析特性

将长链烷基季氮和非高于烷氧链引入同一个分子中,合成了兼有阳离子和非离子表面活性剂特点的低聚合表面活性剂聚氧化丙烯-α-十六烷基二甲基氯化按(PPOCA)和聚氧化丙烯-α-十四烷基二甲基氯化铵(PPOTA)。研究了其基本性质,并试用作光度分析胶束增敏试剂。     

分子结构与化学活性间的定量关系——Ⅲ.脂肪腈与甲醇的加成反应

在甲醇钠的作用下,进行了脂肪腈类与甲醇的加成反应。实验结果表明:加成反应百分率与腈分子中烷基的诱导效应指数形成一正 S 型曲线,而反应的平衡常数及速度常数的对数则分别与烷基的诱导效应指数形成直线关系。根据转化率 S 型曲线上 I_(50)点的位置(10~3I_(50)=10),可以肯定所有烷基腈在这个反应中的转化率都很低,而且反应速度很慢;在卤素、羧基及氰基取代烷基腈中,α-取代物反应迅速且转化率高,但取代基在γ-位置以外,则情况与简单烷腈相近。蒋化率曲线的正 S 走向及速度常数与平衡常数对数的直线的正倾斜度,均表明这个反应是甲醇对腈的亲核子加成反应。     

中性微乳液介质增敏鲁米诺电化学发光研究

磷酸盐缓冲的中性溴化十六烷基三甲基铵-正戊醇-正庚烷微乳液介质体系对鲁米诺的电化学发光有显著的增敏作用,本文对此增敏作用进行了研究,并在此介质体系中采用电化学发光淬灭法测定了生物活性分子褪黑素,此法可用于测定脑白金胶囊中的褪黑素。     

Low-temperature thermal properties of Pb2P2Se6 and Pb1.424Sn0.576P2Se6

The heat capacities of Pb₂P₂Se₆ and Pb_1.424Sn_0.576P₂Se₆ were measured at temperatures between 10 and 320 K for the former and between 10 and 330 K for the latter. The heat capacities values were analyzed by harmonic approximation using the Debye and Einstein functions. They were calculated using 3 Debye and 7, 7, 7, 6 Einstein sets. The calculated heat capacities were in good agreement with the observed ones.     

Excess enthalpies,heat capacities,and excess heat capacities as a function of temperature in liquid mixtures of ethanol + toluene,ethanol + hexamethyldisiloxane,and hexamethyldisiloxane + toluene

The heat capacities of liquid ethanol, toluene, and hexamethyldisiloxane, and of 14 binary mixtures of these were measured at atmospheric pressure at a series of temperatures between 298 and 348 K. In addition, the excess enthalpy was measured for each of the 14 mixtures at room temperature and corrected with the aid of the heat capacities to 298.15 K. The results were represented by empirical equations of a polynomial form. From these equations, the excess heat capacity was derived and the excess enthalpy was calculated, and fitted to equations, as a function of composition at temperatures between 298 and 348 K. All the mixtures are non-ideal as evidenced by the substantial excess enthalpy. The excess enthalpy for the mixtures containing ethanol showed a strong positive temperature dependence, while the variation of temperature between 298 and 348 K had little effect on the excess enthalpy of toluene + hexamethyldisiloxane.     

Computer-aided selection of a polymer matrix for polyaniline conductive blends

The selection of a polymer matrix for a conductive blend with polyaniline and para-toluene sulfonic acid (PANI-pTSA) was performed using molecular simulation techniques, both a fast quantitative structure–properties relationship method as a first screening phase followed by atomistic simulation. Using the atomistic simulation method, the solubility parameters and the heat of mixing of each blend were calculated to enable the determination of compatible matrices in blends with PANI-pTSA, which was validated by experimental scanning electron microscopy fractographs. Based on such calculations, polycaprolactone (PCL)/PANI-pTSA phase diagrams were estimated, showing slight miscibility of polydispersed PANI in PCL, particularly the short chains fraction, at the elevated melt processing temperature. It was suggested that this partial miscibility at the elevated temperature might lead to a conductive network morphology of PANI in PCL at room temperature, because of phase separation and precipitation of soluble PANI molecules, upon cooling and solidification of the melt. © 1998 John Wiley & Sons, Ltd.     

Effect of rapid solidification on heat capacities of Al-Sr alloys

Heat capacities of both the ingot-like and melt-spun Al-Sr alloys have been measured through the temperature range 373 to 1060 K using differential scanning calorimetry. The experimental results show that rapid solidification has a slight effect on the temperature dependence of the heat capacities of the Al-Sr alloys. The heat capacities of the melt-spun Al-Sr alloys increase more slowly than those of the ingot-like alloys with increasing temperature from 373 to 900 K. Furthermore, the effect of rapid solidification on the heat capacities becomes more obvious with increasing Sr concentration in the Al-Sr alloys. The data of the heat capacities between 373 and 900 K have been fitted with the least square method and a linear dependence on temperature was assumed for that temperature range. This revised version was published online in July 2006 with corrections to the Cover Date.     

Calculation of heat capacities of light and heavy water by path-integral molecular dynamics

As an application of atomistic simulation methods to heat capacities, path-integral molecular dynamics has been used to calculate the constant-volume heat capacities of light and heavy water in the gas, liquid, and solid phases. While the classical simulation based on conventional molecular dynamics has estimated the heat capacities too high, the quantum simulation based on path-integral molecular dynamics has given reasonable results based on the simple point-charge/flexible potential model. The calculated heat capacities (divided by the Boltzmann constant) in the quantum simulation are 3.1 in the vapor H2O at 300 K, 6.9 in the liquid H2O at 300 K, and 4.1 in the ice Ih H2O at 250 K, respectively, which are comparable to the experimental data of 3.04, 8.9, and 4.1, respectively. The quantum simulation also reproduces the isotope effect. The heat capacity in the liquid D2O has been calculated to be 10% higher than that of H2O, while it is 13% higher in the experiment. The results demonstrate that the path-integral simulation is a promising approach to quantitatively evaluate the heat capacities for molecular systems, taking account of quantum-mechanical vibrations as well as strongly anharmonic motions.     

氢在沸石上的吸附行为

应用基于Ono-Kondo格子理论得到的通用吸附等温方程, 通过分析氢在不同温度下, 在沸石NaX、CaA、NaA和ZSM-5上的吸附数据, 确定了氢的最大单层吸附容量. 并引入维里吸附方程, 由第二维里吸附系数和圆柱孔的Lennard-Jones(12-6)势模型计算了氢与沸石微孔壁面的作用势. 结果表明, 通用吸附等温方程可较好地描述氢在沸石上的超临界吸附行为, 拟合所得的氢在沸石上的最大单层吸附容量与吸附剂相关, 而与吸附温度无关. 圆柱孔作用势模型计算所得的氢分子在沸石上的吸附作用势与吸附热相近. 氢分子间的作用力表现为吸引力.     

Adsorption of the Ternary Liquid Mixture Ethanol/n-Octane/n-Hexadecane onto Activated Carbon: I. The Adsorption Excess of the Ternary Mixture and of Its Binary Combinations

The adsorption isotherms of the binary mixtures of ethanol/n-Octane, ethanol/n-hexadecane and n-octane/n-hexadecane onto the activated carbon TA 95 were measured at 278 K, 288 K, 298 K and 308 K and described with mathematical functions. About 300 experimental values of the adsorption excess of the ternary mixture ethanol/n-octane/n-hexadecane onto activated carbon TA 95 at 298 K were measured by gas chromatography inside the ternary triangle. The ternary miscibility gap was determined at three temperatures. A good representation of the ternary data and the calculated activity coefficients (using the UNIFAC model) in three-dimensional space was possible with the help of transformation of coordinates. It was possible, too, by utilization of the conception of the quasi two-component representation of the mole fractions with and without miscibility gap. Several influencing factors on ternary adsorption isotherms were discussed for the system ethanol/n-octane/n-hexadecane/TA 95.     

Heat capacities and volumes of methanol+acetonitrile mixtures at 5 and 25°C

Densities and heat capacities of methanol + acetonitrile mixtures were determined over the whole composition range at 5 and 25°C. Apparent and partial molar volumes and heat capacities for both components of the mixture were calculated from these data. These functions for acetonitrile run monotonously over the whole composition range of the mixture at both temperatures, while those for methanol exhibit extrema (volumes-minimum and heat capacities-maximum) at high acetonitrile content. The reasons of the observed behavior of the system are discussed.     

Reversible Melting of Semi-Crystalline Polymers 2. Annealing Near to the Melting Point

Annealing experiments have been carried out at a few degrees below the melting point of different polyethylenes (LDPE, LLDPE, HDPE), of polypropylene (PP) and of Nylon-6. The heat capacities decrease during the annealing, within a 2-4 min time scale, to a lower value which corresponds to the extrapolated heat capacity values obtained for the cooling cycle when the polymer is cooled from the melt. Heat capacities in the heating cycle following the cooling cycle of PP, Nylon-6 and HDPE have the same value as during the cooling section. This is not the case for LDPE and LLDPE. Exothermic total heat flow in the cooling section following the annealing indicates that the crystallisation takes place during the cooling rather than during the annealing period. The total melting enthalpy measured before and after the annealing cycle is the same. The reversing heat flow shows an excellent fit to the change of the crystallinity measured by small angle scattering of synchrotron radiation during a heating cycle at temperatures below the melting peak. A coupled thermodynamic interaction of the crystalline and the amorphous phases is concluded from this study. This kind of interaction is possible at the lateral end of polymeric chains incorporated into the crystalline phase. This is an indication of the portion of tie molecules in the system, i.e. the portion of fringed micelle type of crystalline morphology with respect to that of folded chain lamellae. This revised version was published online in July 2006 with corrections to the Cover Date.     

Ion calorimetry: Using mass spectrometry to measure melting points

Calorimetry measurements have been used to probe the melting of aluminum cluster cations with 63 to 83 atoms. Heat capacities were determined as a function of temperature (from 150 to 1050 K) for size-selected cluster ions using an approach based on multicollision-induced dissociation. The experimental method is described in detail and the assumptions are critically evaluated. Most of the aluminum clusters in the size range examined here show a distinct peak in their heat capacities that is attributed to a melting transition (the peak is due to the latent heat). The melting temperatures are below the bulk melting point and show enormous fluctuations as a function of cluster size. Some clusters (for example, n = 64, 68, and 69) do not show peaks in their heat capacities. This behavior is probably due to the clusters having a disordered solid-like phase, so that melting occurs without a latent heat.