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约翰霍普金斯大学 本研究的目的是探讨表面活性剂的吸附动力学对它们的结构和电荷的依赖性。 将使用两种方法;悬挂气泡技术和振荡气泡技术，这些技术在表面活性剂传质和热力学方面具有精确的理论描述。 随着表面活性剂的扩散和吸收，表面活性剂溶液中悬垂气泡的形状变得越来越长，从而减小了表面轮廓。 这些配置文件是匹配的理论扩散控制松弛的，以获得扩散系数。 平衡数据建立了表面状态方程和吸附等温线。 在振荡气泡法中，形成小的球形气泡，使其平衡，随后通过压电活塞的作用迫使其振荡。 通过对径向压力振荡和气相压力振荡的相位角和振幅比的分析，确定了扩散系数和吸附-脱附系数。 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，将研究同系非离子表面活性剂聚乙氧基化物的表面活性剂吸收的平衡和动力学。 离子型表面活性剂的吸附用于描述表面活性剂的吸附平衡和吸附动力学。 由于德拜长度通常很小，约为1000 A，因此将采用基于薄德拜长度的方法。 扩散通量单独决定子层浓度。 表面活性剂的分区之间的接口和散装根据吸收动力学障碍，这是造成的，在某种程度上，由表面电位。 表面浓度处的电位梯度。 假设瞬时电平衡，因此在双层内电位服从Gouy-Chapman分布。 将采用未适当考虑表面势的表面状态方程和吸附等温线。 这种方法将被用来开发模型的离子表面活性剂吸附在悬垂气泡和振荡气泡的方法。 对于一系列长链酸，将理论与实验进行比较。