Measuring the Kinetics of Surfactant Adsorptive - Desorptive Exchange: The Role of Surfactant Structure and Charge

测量表面活性剂吸附-解吸交换动力学：表面活性剂结构和电荷的作用

• 批准号: 9520972
• 负责人: Kathleen Stebe
• 金额: $ 14.47万
• 依托单位: Johns Hopkins University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-01-15 至 1999-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9520972&HistoricalAwards=false
• 关键词: Measuring; Kinetics; Surfactant; Adsorptive; Desorptive

ABSTRACT CTS-9520972 Kathleen J. Stebe Johns Hopkins University The aim of this study is to probe the dependence of the absorption kinetics of surfactants on their structure and charge. Two methods will be used; the pendant bubble and the oscillating bubble techniques, which have precise theoretical descriptions in terms of surfactant mass transfer and thermodynamics. The shape of a pendant bubble in surfactant solution becomes increasingly elongated as surfactant diffuses and absorbs, reducing the surface profiles. These profiles are matched to theoretical diffusion controlled relaxation's to obtain diffusion coefficients. Equilibrium data establish the surface equation of state and the adsorption isotherm. In the oscillating bubble method a small spherical bubble is formed, equilibrated, and subsequently forced to oscillate by the action of a piezo-piston. Phase angles and amplitude ratios between the radial and gas phase pressure oscillations are analyzed to confirm the diffusivities and to obtain the adsorption-desorption coefficients. For non-ionic surfactants, the theoretical framework to use these techniques has been established. In the first part of this study, the equilibrium and dynamics of surfactant absorption of a homologous series of nonionic surfactants, the polyethoxylates, will be studied. The absorption of ionic surfactants used to describe the equilibrium and dynamics of surfactant absorption. Because Debye lengths are typically small, of order 1000A, an approach based on a thin Debye length will be adopted. Diffusive flux alone determines the sublayer concentration. Surfactant partitions between the interface and the bulk according to an absorption kinetic barrier which is caused, in part, by the surface potential. The potential gradient at the surface concentration. Instantaneous electrical equilibrium is assumed, so the potential obeys a Gouy-Chapman distribution within the double layer. A surface equation of state and adsorption isotherm tha t properly incorporate the surface potential will be adopted. This approach will be used to develop models for ionic surfactant adsorption in the pendant bubble and in the oscillating bubble methods. Theory will be compare to experiment for the a series of the long chain acids.

摘要CTS-9520972 Kathleen J. Stebe Johns Hopkins大学这项研究的目的是探究表面活性剂对其结构和电荷的吸收动力学的依赖性。 将使用两种方法；吊坠气泡和振荡气泡技术，它们在表面活性剂传质和热力学方面具有精确的理论描述。 表面活性剂溶液中吊坠气泡的形状随着表面活性剂扩散和吸收而越来越伸长，从而减少了表面曲线。 这些轮廓与理论扩散控制的松弛相匹配，以获得扩散系数。 平衡数据建立了状态和吸附等温线的表面方程。 在振荡气泡方法中，形成了一个小的球形气泡，并通过压电活塞的作用形成，平衡，然后被迫振荡。 分析了径向和气相压力振荡之间的相角和振幅比，以确认扩散率并获得吸附吸附系数。 对于非离子表面活性剂，已经建立了使用这些技术的理论框架。 在本研究的第一部分中，将研究一系列非离子表面活性剂（聚甲氧基）表面活性剂吸收的平衡和动力学。 用于描述表面活性剂吸收剂的平衡和动力学的离子表面活性剂的吸收。 由于debye长度通常很小，命令为1000a，因此将采用基于稀薄的Debye长度的方法。 仅扩散通量决定了子层浓度。 界面和大块之间的表面活性剂分区根据吸收动力学屏障，部分原因是表面电势引起的。 表面浓度处的潜在梯度。 假定瞬时电平衡，因此潜在的遵守双层层内的小chapman分布。 将采用状态和吸附等温线的表面方程，可正确地包含表面电势。 这种方法将用于开发吊坠和振荡气泡方法中的离子表面活性剂吸附的模型。 理论将与一系列长链酸的实验进行比较。