阳离子表面活性剂在膨润土上的有序化作用及吸附热力学

绘制了不同温度下溴化十四烷基吡啶(MPB)在膨润土上的等温吸附曲线, 探讨了MPB的吸附热力学及作用机理; 并用XRD, FTIR和UV固体漫反射表征了MPB在固相上的有序化作用. 研究结果表明, MPB的吸附热力学、作用机制及有序化过程取决于其在膨润土上的负载量. 不同负载量下标准吉布斯自由能ΔGm0<0, 表明为自发吸附过程, 但存在3个不同阶段. 在低负载量(<0.8CEC)时为吸热吸附[焓变ΔHm0=7.92 kJ/mol, 熵变ΔSm0≈110 J/(K·mol)], 以阳离子交换作用吸附为主; 在高负载量阶段为放热吸附[ΔHm0=-34.41 kJ/mol, ΔSm0≈-50 J/(K·mol)], 以脂肪链间的疏水性相互作用为主; 最大吸附量随温度的升高(278 K→328 K), 从2.8CEC降低为1.5CEC, 相应的ΔHm0=-9.74 kJ/mol. 在负载量由低到高的吸附过程中, 吸附态MPB的状态从无序“液态”逐渐演变为有序“固相”, 吸附过程从熵驱动(ΔSm0>0)过渡为焓驱动(ΔHm0<0).     

Hydroxyl Group Modifies Aggregation Behavior of a Non-ionic Hydro-fluorocarbon Hybrid Surfactant by Disrupting Interracial Water

Two non-ionic hydro-fluorocarbon hybrid surfactants with and without hydroxyl groups were synthesized and compared. They exhibited good thermal stability and superior surface activity. It was observed that the hydroxyl group had a profound effect on modifying the surface tension of their solutions and the morphology of the formed micelles. This effect may be attributed to the rearranging of the alkane group from above the air/aqueous surface to below it and the disrupting of the interfacial water structure induced by the hydroxyl groups. This work provides a strategy to weaken the immiscibility between hydrocarbon and fluorocarbon chains by modifying their orientational structure at the interface, thus it is helpful for the design of surfactants with varied interfacial properties.     

Thermodynamics of Transfer of Some Alkyl Acetates from Water to Water–Ethanol Mixtures

Summary.  The solubility of methyl acetate (MeOAc), ethyl acetate (EtOAc), 1-propyl acetate(1-PrOAc), 1-butyl acetate (1-BuOAc), 2-methyl-1-propyl acetate (iso-BuOAc), 2-butyl acetate (sec-BuOAc), 2-methyl-2-propyl acetate (tert-BuOAc), 1-pentyl acetate (1-PeOAc), and 1-hexyl acetate(1-HeOAc) in 2.5, 5.0, 7.5, and 10.0 weight per cent of ethanol in water were determined at 298.2 K. The solubility of the same compounds, except for tert-BuOAc, 1-PeOAc, and 1-HeOAc, was determined as a function of temperature at 10.0 weight per cent of ethanol in water. From the solubility measurements the standard Gibbs energy (), enthalpy (), and entropy () of transfer were determined. The calculated thermodynamic functions show that the predominant factors in the transfer of alkyl acetate molecules are the transfer of the cavity and the hydrophobic interaction of the non-polar alkyl chain. Scaled particle theory calculations were used to determine the thermodynamics of cavity transfer, which were combined with the experimental total transfer quantities to obtain the corresponding interaction transfer quantities. It was found that the Gibbs energy of interaction for the transfer is negative, whereas the enthalpy and entropy of interaction for the transfer are positive; almost complete compensation of enthalpy and entropy components occurs. Received September 27, 2001. Accepted (revised) December 20, 2001     

Thermodynamics of Transfer of Some Alkyl Acetates from Water to Water–Ethanol Mixtures

 The solubility of methyl acetate (MeOAc), ethyl acetate (EtOAc), 1-propyl acetate(1-PrOAc), 1-butyl acetate (1-BuOAc), 2-methyl-1-propyl acetate (iso-BuOAc), 2-butyl acetate (sec-BuOAc), 2-methyl-2-propyl acetate (tert-BuOAc), 1-pentyl acetate (1-PeOAc), and 1-hexyl acetate(1-HeOAc) in 2.5, 5.0, 7.5, and 10.0 weight per cent of ethanol in water were determined at 298.2 K. The solubility of the same compounds, except for tert-BuOAc, 1-PeOAc, and 1-HeOAc, was determined as a function of temperature at 10.0 weight per cent of ethanol in water. From the solubility measurements the standard Gibbs energy (), enthalpy (), and entropy () of transfer were determined. The calculated thermodynamic functions show that the predominant factors in the transfer of alkyl acetate molecules are the transfer of the cavity and the hydrophobic interaction of the non-polar alkyl chain. Scaled particle theory calculations were used to determine the thermodynamics of cavity transfer, which were combined with the experimental total transfer quantities to obtain the corresponding interaction transfer quantities. It was found that the Gibbs energy of interaction for the transfer is negative, whereas the enthalpy and entropy of interaction for the transfer are positive; almost complete compensation of enthalpy and entropy components occurs.     

Thermodynamics of Addition Polymerization Processes

The polymerizability of compounds such as 1,l-disubstituted ethylenes, aldehydes, ketones, isocyanates, and five- and six-membered ring compounds is determined largely by thermodynamic considerations. The transition from non-polymerizability to polymerizability, correspondlng to a change in the sign of ΔG, is often quite sharp. Factors which generally make the free energy of polymerization more negative, and which therefore favor polymerization, are low temperature, high pressure, and high monomer concentration. Additional driving force is sometimes available if the monomer is in the supercooled (glassy) state rather than the crystalline state, or if the polymer crystallizes on formation. Alkyl substituents have an unfavorable effect on polymerizability; halogen substituents have a favorable effect. Many monomers which do not homopolymerize for thermodynamic reasons will copolymerize with a second monomer to the extent of forming copolymers containing 50 or even 66 mol per cent of the first monomer.     

阴离子表面活性剂在油水界面聚集的分子动力学模拟

用分子动力学方法模拟了油、水和阴离子表面活性剂组成的混合溶液从初始“均相”到“油水两相”分离的动力学过程, 研究了十二烷基苯磺酸钠(SDBS)在界面分离过程中的作用. 模拟发现, 油水两相能够在短时间内分离达到平衡, 形成一个明显的油水界面; 在SDBS存在情况下, 油水界面的分离时间随着SDBS浓度的增加逐渐增加, 达到平衡时SDBS会在界面处形成一个明显的界面膜, 并对油水界面处的水分子有限制作用. 模拟表明, 分子动力学方法可以作为实验的一种补充, 为实验提供必要的微观分子结构信息.     

The Effect of Water Addition on the Electrosurface Properties of Quartz in Solutions of Alkali Metal Bromides in Ethanol

Electrosurface properties (the -potential and surface conductivity) of quartz particles in water–ethanol solutions of CsBr, NaBr, and LiBr with concentrations C = 10^–5–10^–2 M are studied. The (log C) dependences plotted from the results of electrophoretic measurements with allowance made for the particle surface conductivity demonstrate that, when water content in the aforementioned solutions increases from 4 to 40 vol %, the -potential of quartz becomes more negative and the isoelectric point shifts toward higher electrolyte concentrations, which increase in the following series: CsBr < NaBr < LiBr. This shift of the isoelectric point is explained by a decrease in the specific interaction of the alkali metal cations with the quartz surface because of a rise in the degree of their hydration (supersolvation).     

Kinetics of Aggregation and Relaxation in Micellar Surfactant Solutions

Theoretical results published in the last 17 years on the kinetics of aggregation and relaxation in micellar surfactant solutions have been reviewed. The results obtained by the analytical and direct numerical solution of the Becker–Döring kinetic equations and the Smoluchowski generalized equations, which describe different possible mechanisms of aggregation and relaxation on all time scales from ultrafast relaxation while reaching the quasi-equilibrium in the region of subcritical molecular aggregates to the last stage of slow relaxation of micelles to the final aggregated state, have been considered in detail. The droplet model and the model linear with respect to aggregation numbers have been used for the work of aggregation to describe the dynamics of the rearrangement of micellar systems consisting of only spherical, only cylindrical, and coexisting spherical and cylindrical aggregates, with the dynamics being both linear and nonlinear with respect to deviations from equilibrium. The results of molecular simulation of the rearrangement kinetics of micellar systems subjected to initial disturbance have been reviewed.     

Aerosol-OT在水和聚乙二醇-200混合溶液中有序结构转变及影响因素研究

通过电导、流变学方法等研究了温度和表面活性剂浓度对双(2-乙基己基)磺基琥珀酸钠(AOT)、水和聚乙二醇-200(PEG-200)体系有序结构形成和转变的影响。结果发现,在室温下高浓度AOT溶液中出现凝胶结构。当AOT的浓度为400mmol/kg以上时,随着温度的升高,观察到体系从透明粘稠到稍浑浊再到透明低粘度的过程,结合AOT的双链结构并通过流变实验验证了网络结构的形成,推测该体系在微观上经历了从凝胶到囊泡再到胶束的转变过程。当AOT的浓度为200~400 mmol/kg时,随着温度的升高,出现了凝胶和胶束混合体系到胶束体系的转变过程。     

用吸收光谱法研究亚甲蓝在表面活性剂存在时的聚合状态

应用紫外－可见吸收光谱研究了光敏试剂亚甲蓝在溶液中的聚合状态及其与表面活性剂之间的关系。当添加阴离子表面活性剂的浓度于其临界胶束浓度时，亚甲蓝二聚体的比例将出现一极大值；用环己烷剂萃取后，测得亚甲蓝二聚体的吸收光谱，其最大吸收波长位于６０４ｎｍ。     

Thermodynamic Analysis of Trisiloxane Surfactant Adsorption and Aggregation Processes

The trisiloxane polyether surfactant (3-[3-(hydroxy)(polyethoxy)propyl]-1,1,1,3,5,5,5 -heptamethyltrisiloxane) (TS-EO12) was successfully synthesized by a hydrosilylation reaction in the presence of Karstedt catalyst. The structural analysis of the surfactant was done by ¹H-NMR, ¹³C-NMR, ²⁹Si-NMR and FT-IR analysis. In addition the thermal stability of TS-EO12 was studied by the thermogravimetric measurements. On the one hand the surface properties of TS-EO12 at the water-air interface were investigated by surfactant aqueous solutions surface tension measurements carried out at 293 K, 303 K and 313 K, and on the other the aggregation properties were analyzed based on the solubilization properties of TS-EO12 aggregates at different temperatures. On the basis of the obtained thermodynamic parameters of adsorption and micellization of studied surfactant the temperature impact on its surface and volume properties were deduced. It was proved that the tendency of the studied surfactant molecules to adsorb at the water-air interface and to form micelles weakens with decreasing temperature. It was also concluded that the structure of the adsorption layer changes with temperature. Optical microscopy measurements were used for the TS-EO12 micelle morphology determination.     

Gemini 阴离子表面活性剂水溶液的聚集性质

合成了一种Gemini阴离子表面活性剂,测定了其临界胶束浓度cmc和cmc时的表面张力γcmc,与传统的单基表面活性剂相比,其临界胶束浓度降低了一个数量级,具有突出的降低水的表面张力的效率;研究了该种Gemini表面活性剂的浓度对于胶束聚集数的影响,结果表明,随着浓度的增加,胶束聚集数出现了一个极大值,同时观察到液晶微相的生成.     

血卟啉在胶束介质中的聚集状态研究

用光谱法研究了光敏剂血卟啉在水溶液中的聚集状态，并以胶束作为生物膜模型，探讨了血卟啉在胶束介质中的聚集状态状态变化，用原子力显微镜研究了血卟啉聚集状态的微观结构及其在胶束介质中的聚集状态。     

Kinetics and Thermodynamics of Ethanol Production by Saccharomyces cerevisiae MLD10 Using Molasses

In this study, we have used ultraviolet (UV) and γ-ray induction to get a catabolite repression resistant and thermotolerant mutant with enhanced ethanol production along with optimization of sugar concentration and temperature of fermentation. Classical mutagenesis in two consecutive cycles of UV- and γ-ray-induced mutations evolved one best catabolite-resistant and thermotolerant mutant Saccharomyces cerevisiae MLD10 which showed improved ethanol yield (0.48?±?0.02 g g^?1), theoretical yield (93?±?3 %), and extracellular invertase productivity (1,430?±?50 IU l^?1 h^?1), respectively, when fermenting 180 g sugars l^?1 in molasses medium at 43 °C in 300 m³ working volume fermenter. Ethanol production was highly dependent on invertase production. Enthalpy (ΔH*) (32.27 kJ M^?1) and entropy (ΔS*) (?202.88 J M^?1 K^?1) values at 43 °C by the mutant MLD10 were significantly lower than those of β-glucosidase production by a thermophilic mutant derivative of Thermomyces lanuginosus. These results confirmed the enhanced production of ethanol and invertase by this mutant derivative. These studies proved that mutant was significantly improved for ethanol production and was thermostable in nature. Lower fermentation time for ethanol production and maintenance of ethanol production rates (3.1 g l^?1 h^?1) at higher temperature (43 °C) by this mutant could decrease the overall cost of fermentation process and increase the quality of ethanol production.     

搅拌萃取–分光光度法检测水环境中阴离子表面活性剂

建立搅拌萃取–分光光度法快速检测水环境中阴离子表面活性剂的含量。用三氯甲烷以800~1 200 r/min搅拌萃取水样与亚甲蓝溶液合成的活性物质,搅拌时间为2 min,静置分层后经脱脂棉过滤,待测。阴离子表面活性剂质量浓度在0.050~0.500 mg/L范围内与吸光度线性良好,相关系数大于0.999 0,方法检出限为0.010 mg/L。选择饮用水源水、农村地下水、湖泊水、城市河道水作为研究对象,平行检测结果的相对标准偏差(RSD)为1.9%~6.5%(n=6),加标回收率为91.3%~110%;对标准物质检测结果的相对误差为–2.3%~3.5%,满足实验室分析质量控制要求和现行地表水、地下水质量标准的评价要求。该方法与国标检测方法相比,在准确度、精密度、灵敏度、分析效率及试剂用量方面均有明显优势,具有推广应用价值。     

也谈乙醇中含水的检验

“化学教育”1989年第3期,“关于乙醇中含水检验的商榷”一文(以下简称黎文),认为普通乙醇(95％)中含水量不能用无水硫酸铜来检验,即使含水量接近50％都不能使无水硫酸铜变蓝,并从实验和理论上加以解释。我们认为,上述观点无论从理论解释还是实验结论来说,都缺乏根据,即使在含水量低于普通乙醇(如98％乙醇)的情况下,也是可以用无水硫酸铜检出水的。首先,我们认为,黎文中所述的实验是不准确的。我们按所述的实验方法,反复多次验证所得结果与黎文结果相反。     

扩张流变法研究表面活性剂在界面上的聚集行为

近年发展起来的界面流变测定技术在研究界面性质方面具有许多独特之处.本文结合我们的工作,总结了近年来有关该技术在表面活性剂界面聚集行为研究中的应用,讨论了扩张频率、表面活性剂浓度及疏水链长、无机盐和温度对表面扩张流变行为的影响,同时探讨了小分子表面活性剂与高分子表面活性剂表面扩张流变行为的区别以及小分子表面活性剂在气/液界面与液/液表面的扩张流变性的差异.大量研究表明,借助于界面流变性的测定不仅可以研究发生在界面上和界面附近的微观弛豫过程,而且可以探讨界面上超分子聚集体的形成,进而为乳状液和泡沫等分散体系的稳定性提供依据.     

Turbulent Aggregation of Titania in Water

This paper deals with the application of two in situ particle sizing methods to the study of aggregation of titanium dioxide in turbulent aqueous solutions. Turbidity measurements are used to characterize aggregation of diluted suspensions (solid volume fraction less than 10(-4)). Analysis of backscattered light can be applied to highly concentrated suspensions. Because in situ measurements are possible, the aggregation process can be followed from its beginning to the final steady state which is always observed. The influences of stirring rate and solid volume fraction on the aggregation dynamics are presented. They are interpreted in the framework of a model of aggregation which takes into account the morphology and the related optical properties of the aggregates and the physical and hydrodynamic interactions between aggregates. The complex relationship between aggregate restructuring and aggregation on one hand, and fragmentation on the other hand, is considered. Copyright 2000 Academic Press.     

Aggregation of Rhodamine B in Water

Protolytic and associative equilibria in aqueous solutions of rhodamine B were studied. The curves of potentiometric titration with NaOH solution of the dye hydrochloride within the 5 ×10^-4-3 ×10^-2 M range and at an ionic strength of 0.1 M (NaCl or KCl) were treated by chemometric methods of successive modification of the equilibrium system models with regard to spectrophotometric data. The most probable value of the equilibrium constants of the reaction iH⁺ + jR H _i R _j ⁱ⁺ were determined.