表面活性剂在气/液界面上扩散控制的吸附动力学(英文)

For the diffusion-controlled adsorption, the expression of dynamic surface adsorption P（t） was ob- tained by solving the diffusion equation. Two cases, i.e. the short and long time limits, were mainly discussed in this paper. From the measured dynamic surface tension of aqueous surfactant sodium dodecyl sulfate （SDS） solutions at 25 ℃, the adsorption kinetics of SDS at air/solution interface was studied. It was proved that for both of the short and long time limits, the adsorption process of SDS was controlled by diffusion.     

表面活性剂在气/液界面上的吸附动力学

在求解扩散方程的基础上,推导出了描述气 液界面吸附的动态吸附量Γ(t)表达式,并重点讨论了吸附的初始阶段和最终阶段两种极限情况。试验测定了25℃下表面活性剂C12E7[分子式CH3(CH2)11(OCH2CH2)7OH]水溶液的平衡及动态表面张力,结合理论推导,考察了C12E7在气 液界面的吸附过程。试验结果表明,气 液界面吸附过程在最初(极短时间)阶段是扩散控制,在吸附过程的后期(长时间)则出现了扩散 吸附混合控制。     

The Adsorption of a Polystyrene-b-Polyisoprene Block Copolymer at the n-Hexadecane/Air Interface

Surface-tension measurements were used to investigate the surface adsorption and micellisation of a polystyrene-b-polyisoprene block copolymer in n-hexadecane which is a selectively bad solvent for polystyrene. Measurements were made over a range of concentrations (1.29–2.88)x10^?4 mol dm^?3 and temperatures 25–40°C. The block copolymer was found to be positively adsorbed at the n-hexadecane/air interface. The linearity of plots of γ against In c just below the critical micelle concentration (c.m.c.) indicated an approximately constant surface concentration. The area per block copolymer molecule at the surface had an average value of 4.1 nm². A plot of In (c.m.c.) against T^?1 gave a value for the standard enthalpy of micellisation of -41.9.3.0 kJ per mole of copolymer chains. The standard entropy contribution (-TΔSΔ) to the standard free energy of micellisation was found to be 19.7.3.0 kJ mol^?1. These thermodynamic values are in good agreement with results obtained earlier for this system by light scattering and calorimetry.     

Tween 80分子在气-液界面上的动态吸附量研究

从Tween80水溶液的动态表面张力计算出动态吸附量,发现动态表面状态方程的适用性与溶液浓度有关。对于小于临界胶束浓度的Tween80水溶液,浓度位于0.0107~0.0938molm-3的较大范围内,动态吸附量Γt遵从由Szyszkowski吸附等温式导出的动态表面状态方程,低于0.0055molm-3时,实验测定的动态吸附量与各动态表面状态方程的计算值均不符。     

扩展球形溶液表面上decanoyl-N-methylglucamine的吸附动力学

A general expression of the dynamic surface adsorption [Г（t）] on the expanding spherical surface was derived by solving the corresponding diffusion equation under different initial and boundary conditions. Different from the result of the still spherical surface, two factors （smaller than 1） appeared in the equation for the short time adsorption. Using the derived results, the adsorption kinetics of aqueous decanoyl-N-methylglucamine （Mega-10） solution was studied. In the short time region （t→0）, a good agreement of experimental results with the theory was reached and the adsorption was controlled by diffusion.     

表面活性剂在固液界面吸附研究的某些新进展

本文综述了离子型表面活性剂以及阳离子与非离子型表达活性剂的混合体系在固液界面吸附情况。     

Gemini表面活性剂在固液界面的吸附及增溶作用

介绍了一类新型表面活性剂———Gemini表面活性剂。这类表面活性剂具有特殊的分(离)子结构,其分(离)子由两(或三)条疏水链、两个亲水基和一个连接基组成。综述了Gemini表面活性剂在固液界面的吸附及增溶作用,其在固液界面的吸附及增溶作用与固体表面的性质及其分(离)子结构有很大关系。     

两种Gemini表面活性剂在气／液界面的混合单分子膜

用Langmuir膜天平测定了双头基四疏水链的季铵盐Gemini表面活性剂2C12-8-2C12·2Br和羧酸型Gemini表面活性剂c11pPHCOOH在气／液界面的表面压(π)-每个分子平均占据面积(A)的等温线,考察了压缩模量(ε)、过剩面积(△AE)、过剩自由能(△GE)等热力学参数随混合体系组成的变化。结果表明,纯组分体系和混合体系均形成液相扩展态单分子膜,混合体系的组成显著影响气／液单分子膜的性质以及组成膜的分子之间的相互作用。     

Adhesion of an Air Bubble to Quartz Surface in Aqueous Solution of Aliphatic Amine Hydrochloride

Measurements of the force of air bubble detachment from a quartz surface in aqueous solutions of decylamine hydrochloride (DAC1), dodecylamine hydrochloride (DDAC1) and tetradecylamine hydrochloride (TDAC1) were made in the concentration range from 0 to 200mg/dm³. At the same time, the instantaneous contact angle for the system quartz-air bubble-aqueous solution of aliphatic amine hydrochloride was photographed at the moment of detachment. Wetting contact angles for the system quartz-air bubble-aqueous solution of DDAC1 were also measured. On the basis of the measured values of the instantaneous angle and surface tension of the solutions studied, the changes of polar components of surface free energy of quartz/monolayer water film under the influence of adsorption of molecules of aliphatic amine hydrochloride (RAC1) from aqueous solution were calculated and compared with the literature data. Using these data, the force of air bubble detachment from the quartz surface in the presence of RAC1 was also calculated and compared with the measured force, obtaining a good agreement. From the studies and calculations it appears that a little addition of RAC1 to water considerably changes the stability of the system quartz-air bubble-solution, and that this change is first of all caused by reduction of a polar component of the surface free energy of quartz/monolayer water film as a result of adsorption of RAC1 molecules in the negative places of such a surface. As a result of RAC1 adsorption this surface becomes similar to that of paraffin.     

Adhesion of an Air Bubble to Quartz Surface in Aqueous Solution of Aliphatic Amine Hydrochloride

Measurements of the force of air bubble detachment from a quartz surface in aqueous solutions of decylamine hydrochloride (DAC1), dodecylamine hydrochloride (DDAC1) and tetradecylamine hydrochloride (TDAC1) were made in the concentration range from 0 to 200mg/dm³. At the same time, the instantaneous contact angle for the system quartz-air bubble-aqueous solution of aliphatic amine hydrochloride was photographed at the moment of detachment. Wetting contact angles for the system quartz-air bubble-aqueous solution of DDAC1 were also measured. On the basis of the measured values of the instantaneous angle and surface tension of the solutions studied, the changes of polar components of surface free energy of quartz/monolayer water film under the influence of adsorption of molecules of aliphatic amine hydrochloride (RAC1) from aqueous solution were calculated and compared with the literature data. Using these data, the force of air bubble detachment from the quartz surface in the presence of RAC1 was also calculated and compared with the measured force, obtaining a good agreement. From the studies and calculations it appears that a little addition of RAC1 to water considerably changes the stability of the system quartz-air bubble-solution, and that this change is first of all caused by reduction of a polar component of the surface free energy of quartz/monolayer water film as a result of adsorption of RAC1 molecules in the negative places of such a surface. As a result of RAC1 adsorption this surface becomes similar to that of paraffin.     

气-液界面间表面活性剂物质的吸附状态

利用Gibbs吸附公式,通过测量溶液浓度和表面张力可以计算最大吸附量时表面活性剂的表面吸附量,进而计算得到每个分子所占有的表面积;通过与分子本身大小比较能够推测出分子在表面的吸附状态。本文利用文献值,通过计算得出常见的离子型、非离子型及Gemini型表面活性剂在CMC时的平均分子占有面积,同时将具有表面活性的丁醇一并比较。结果发现,各类分子在表面的占有面积为头基的1~2倍,紧密程度为Gemini型离子型丁醇非离子型;同类型之间,支链较多且取代基分子量较大时排列疏松。同时,温度对其影响也进行了对比分析。     

十六烷基溴化吡啶水溶液的动态吸附量研究

滴体积法测定了十六烷基溴化吡啶(CPB)水溶液的动态表面张力。不同浓度的溶液遵从不同的动态表面状态方程,浓度低于0.031 mol·m~(-3)时,动态吸附量T_1遵从由Henry吸附等温式导出的动态表面状态方程;浓度位于0.031～0.560mol·m~(-3)的较大范围内,T_1遵从由Langmuir和Freundlich等温式导出的动态表面状态方程;在更高的浓度下(如0.683 mol·m~(-3)),T_1只遵从从Langmuir等温式得出的表面状态方程。     

分子动力学模拟在蛋白质固体表面吸附构象转变中的应用

蛋白质在固液界面上吸附过程中,溶液中的蛋白质分子不仅在自身之间存在着相互作用,而且还与水分子和固体表面之间发生着复杂的相互作用,蛋白质分子的生物活性也会发生变化。本文采用分子动力学模拟的方法对这一构象变化的复杂过程进行研究,并以聚十赖氨酸固液界面吸附过程为例进行了分子动力学模拟计算。     

一种新型Bola型表面活性剂在固液界面吸附行为的研究

研究了bola型表面活性剂———聚丙二醇二乙酸钠在纳米碳酸钙上的吸附行为,并考察了疏水链长度、无机盐加入对吸附的影响,结果表明聚丙二醇二乙酸钠的吸附等温线为LS型,是多分子层吸附;疏水链的增长、无机盐的加入均可使聚丙二醇二乙酸钠在纳米碳酸钙表面的吸附更易达到吸附饱和。     

FC/CH表面活性剂复配在电子布化学处理中的应用

论述了电子布化学处理采用氟碳表面活性剂（FC）、碳氢表面活性剂（CH）与硅烷偶联剂水解液复配的原因。并通过实例比较了采用不同的FC/CH表面活性剂进行复配对动态表面张力的影响。同时,作者研究了如何选择FC以及如何将FC/CH复配以达到动静态表面张力俱佳的效果。因此使用FC/CH表面活性剂复配能达到降低动态和静态表面张力的目的,提升电子布的处理品质。     

利用最大泡压法研究扩散控制的溶液表面吸附动力学

In studying the diffusion-controlled adsorption kinetics of aqueous surfactant solutions at the air/solution surface by means of the maximal bubble pressure method, Fick's diffusion equation for a sphere should be used. In this paper the equation was solved by means of Laplace transformation under different initial and boundary conditions. The dynamic surface adsorption (t) for a surfactant solution, which was used to describe the diffusion-controlled adsorption kinetics at the solution surface, was derived. Different from the planar surface adsorption, the dynamic surface adsorption (t) for the short time consists of two terms: one is the same as WardTordai equation and the other reflects the geometric effect caused by the spherical bubble surface. This effect should not be neglected for the very small radius of the capillary. The equilibrium surface tension γeq and the dynamic surface tension γ(t) of aqueous C10E6 [CH3(CH2)9(OCH2CH2)6OH] solution at temperature 25°C were measured by means of Wilhelmy plate method and maximal bubble pressure method respectively. As t → 0, the theoretical analysis is in good agreement with experimental results and the dependence ofγ(t)on(√t r0/√πD)2 is linear.     

Relationship of structure to properties of surfactants. 16. Linear decyldiphenylether sulfonates

The properties of some well-characterized sodium linear decyldiphenylether (C₁₀DPE)sulfonates have been studied. Among the properties investigated are dynamic and equilibrium surface tension, critical micelle concentration (CMC), area per molecule at the aqueous solution/air interface, wetting time by the Draves technique, foaming by the Ross-Miles method, solubilization, and hydrotropy. The decyldiphenylether moiety appears to be equivalent to a terminally substituted straight alkyl chain of 16 carbon atoms. The trialkyl- and dialkyl-mono-sulfonates have solubilities of < 0.01 g/dm³ in water, but are readily soluble in hexane. The didecyldiphenyl ether disulfonate (DADS) has a very low CMC value (1.0 × 10⁻⁵ mol dm⁻³) in aqueous 0.1 N Na⁺ solution (NaCl), characteristic of surfactants with two hydrophilic and two hydrophobic groups. It also has a much larger area per molecule at the aqueous solution/air interface than the monodecyldiphenyl-ether monosulfonate (MAMS) and a much higher surface tension at the CMC. MAMS has a much lower surface tension at a surface age of 1 second (γ_1s) than either DADS or the monodecyldiphenylether disulfonate (MADS). In agreement with γ_1s and γ_eq values, wetting times increase in the order: MAMS < DADS < MADS and initial foam heights decrease in the order: MAMS > DADS > MADS. Solubilization for three water-insoluble surfactants decreases in the order: DADS > MAMS > MADS, while hydrotropy is most pronounced with the disulfonates.     

Kinetics of Charge-Transfer Reactions at Nanoscopic Electrochemical Interfaces

After several decades of intensive studies, the questions about the magnitudes of rate constants of rapid heterogeneous electron transfer (ET) and ion transfer (IT) reactions remain open. The fabrication of nanometer-sized metal electrodes and nanopipets enabled electrochemical studies of rapid charge transfer processes at solid/liquid and liquid/liquid nanointerfaces. The nanoelectrochemical techniques offer numerous advantages such as fast mass-transfer rate and simplified analysis of data obtained under steady-state conditions. At the same time, kinetic data obtained at nanointerfaces may be affected by double layer effects, deviations from classical electrochemical theory, and other size-related phenomena. Nanoelectrochemical measurements are also plagued by difficulties in characterizing nanometer-sized interfaces and conductor/insulator boundaries. In this review, we discuss the results of fast electron and ion transfer kinetics measurements at nanointerfaces, along with related reliability problems and some approaches to fixing them.     

高分子在固体表面吸附的分子模拟

综述了分子模拟研究高分子在固体表面吸附的应用,简单介绍了分子模拟的基本原理及其常用的几种方法,并分别介绍了分子模拟在研究高分子吸附构象以及吸附动力学方面的应用。