GOALI: SURFACTANT-MEDIATED ELECTROPHORETIC PROPERTIES OF APOLAR DISPERSIONS

目标：表面活性剂介导的非极性分散体的电泳特性

• 批准号: 1160138
• 负责人: Sven Behrens
• 金额: $ 26.65万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-05-15 至 2015-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1160138&HistoricalAwards=false
• 关键词: GOALI; SURFACTANT; MEDIATED; ELECTROPHORETIC; PROPERTIES

Abstract#1160138Sven H. Behrens Intellectual Merit Mobile ions and electric surface charges are ubiquitous in water and other polar liquids, but should play no role in apolar liquids, where the energetic cost of charge dissociation is typically too large for thermal activation. Defying this conventional wisdom, some surfactant additives can raise the conductivity of apolar liquids by many orders of magnitude and promote electrical charging of immersed solid surfaces or of suspended colloidal particles. The resulting ability to direct particle motion with applied electric fields is crucial, e.g. for liquid toners and electrophoretic displays but neither the mechanism of particle charging nor the effect of the directing field are currently understood. Building on the PI's experience in measuring and modeling electrostatic interactions, and with strong support from the Hewlett-Packard team developing the next generation of color electrophoretic displays, the investigators propose to unravel the fundamental principles of particle charge and field-driven motion in apolar surfactant solutions. The working hypothesis in this project is that surfactants simultaneously influence the electric behavior of apolar dispersions in at least three ways: by promoting surface charging via acid-base interaction, by solubilizing surface counterions inside of surfactant aggregates, and by forming micellar ions in the solution bulk via charge disproportionation. They aim at disentangling these mechanisms with an original suite of experimental techniques accessing separately the charge contained in the bulk solution and on the particle surface, the particle-particle and particle-field interaction, as well as the amount of adsorbed surfactant and residual water. Using particles of different surface characteristics and surfactants with systematically varied architecture will allow the investigators to find the elusive answer to the question what makes some surfactants more effective than others at imparting charge and electrophoretic mobility on a given particle type. Thermodynamic models for the charging reaction and surfactant adsorption will be tested against their experiments. Broader Impact The proposed study should significantly expand the understanding of charging processes in apolar liquids and on immersed solid surfaces. Applications range from safety measures in fuel transportation and the design of electrophoretic displays and electronic skins to the stabilization of emulsions with solid particles relevant for food formulation and skin care creams as well as for oil recovery and oil spill remediation. The research directly touches on our understanding of surfactants surrounding us in everyday life, and can easily be illustrated with examples accessible to non-experts.Building on this educational potential, the PI works with pre-schoolers through first graders in a predominantly (97%) African-American school via hands-on science workshops designed to reinforce the natural curiosity in these young children. An ongoing close collaboration with the classroom teachers makes these workshops more impactful by enhancing classroom activities with related science materials; and the most successful demonstrations are captured in science demo kits with appropriate materials and instructions for the teachers to use in later years independently of the PI. The PI also supports diversity at the collegiate level by recruiting female students to his lab, which has had a majority of women at any given time, and has a history of involving African American undergraduates in its research.

流动离子和表面电荷在水和其他极性液体中普遍存在，但在极性液体中不应发挥作用，因为极性液体中电荷解离的能量成本通常太大，无法进行热活化。一些表面活性剂添加剂可以将极性液体的导电性提高许多个数量级，并促进浸入固体表面或悬浮胶体颗粒的电荷。由此产生的用外加电场引导粒子运动的能力是至关重要的，例如，对于液体调色剂和电泳显示器来说，但粒子充电的机制和定向场的影响目前都还不清楚。基于PI在测量和模拟静电相互作用方面的经验，并在开发下一代彩色电泳显示器的惠普团队的大力支持下，研究人员建议揭示极性表面活性剂溶液中粒子电荷和场驱动运动的基本原理。本项目的工作假设是，表面活性剂至少以三种方式同时影响极性分散体的电行为：通过酸碱相互作用促进表面充电，通过溶解表面活性剂聚集体内部的表面反离子，以及通过电荷歧化在溶液体中形成胶束离子。他们的目标是通过一套原始的实验技术来解开这些机制的纠缠，这些实验技术分别访问大块溶液和颗粒表面所含的电荷，颗粒-颗粒和颗粒-场的相互作用，以及吸附的表面活性剂和残余水的数量。使用具有不同表面特征的颗粒和具有系统不同结构的表面活性剂，将使研究人员能够找到难以捉摸的问题的答案，即是什么使某些表面活性剂比其他表面活性剂更有效地在给定颗粒类型上传递电荷和电泳迁移率。充电反应和表面活性剂吸附的热力学模型将根据他们的实验进行测试。该研究将极大地扩展对极性液体和浸没固体表面的充电过程的理解。应用范围从燃料运输的安全措施，电泳显示器和电子皮肤的设计，到与食品配方和护肤霜相关的固体颗粒乳液的稳定，以及石油回收和漏油补救。这项研究直接触及了我们对日常生活中我们周围的表面活性剂的理解，并且可以很容易地用非专业人士可以理解的例子来说明。在这种教育潜力的基础上，PI与一所以非洲裔美国人为主（97%）的学校的学龄前儿童到一年级学生合作，通过实践科学研讨会，旨在加强这些孩子天生的好奇心。与课堂教师的持续密切合作，通过使用相关科学材料加强课堂活动，使这些讲习班更具影响力；最成功的演示是在科学演示工具包中进行的，其中包含适当的材料和指导，供教师在以后的几年独立于PI使用。PI还通过招募女学生到他的实验室来支持大学层面的多样性，他的实验室在任何时候都是女性占多数，并且有让非裔美国本科生参与研究的历史。