Impact of Specific Counterion Binding on Surfactant Aggregates and Polyelectrolytes: Beyond Electrostatic Screening Effects

田纳西诺克斯维尔大学的Linda Magid得到了实验物理化学项目的支持，该项目的研究重点是反离子结构的变化如何改变表面活性剂聚集体的三维结构(形状和构象)，以及这些变化如何影响其溶液的宏观性质(如粘度、去污力和润湿性)。表面活性剂在水溶液中自组装形成各种分子形状的聚集体，包括球状、延伸的蠕虫状结构、由蠕虫和囊泡组成的分支网络以及双层结构。离子表面活性剂聚集体带有净电荷，与传统聚电解质有许多相似之处。这项研究的核心是一种通过改变表面活性离子的化学结构来调节聚集体结构的技术。特别强调了解哪些结构特征导致聚集分支，以及哪些结构特征导致蠕虫状结构收缩回球体。将使用散射方法(光、X射线和中子)、显微镜和核磁共振光谱来研究聚集体的微观结构和动力学。将合成用于中子散射实验的氢化表面活性剂和聚电解质。将通过两项课程开发活动促进教学和培训，使高中生和本科生受益。了解表面活性剂聚集体的性质具有重要的基础意义和实用价值。表面活性剂聚集体广泛应用于个人护理产品、药物输送和其他各种应用。这项研究的一个长期目标是建立一种“化学词典”，使表面活性剂科学家能够理解如何通过简单地改变反离子含量来操纵像粘性这样的本体性质。此外，这项研究对于理解反离子对DNA等生物分子灵活性的影响具有重要联系。

Linda Magid of the University of Tennessee Knoxville is supported by the Experimental Physical Chemistry Program for research that focuses on how changes in counterion structure change the three-dimensional structure (shape and conformation) of surfactant aggregates, and how these changes affect the macroscopic properties (such as viscosity, detergency, and wetting) of their solutions. Surfactants self-assemble in aqueous solution to form aggregates with a variety of molecular shapes, including spheres, extended wormlike structures, branched networks of worms and vesicles, and bilayer structures. Ionic surfactant aggregates carry a net electrical charge and have a variety of similarities to conventional polyelectrolytes. At the core of this research is a technique for tuning the aggregates' structures by changing the chemical structure of the surfactant ions. Special emphasis is placed on understanding which structural features lead to aggregate branching, and which lead to shrinking of wormlike structures back to spheres. Scattering methods (light, x-rays, and neutrons), microscopy, and nuclear magnetic resonance spectroscopy will be used to investigate both the microstructure and dynamics of aggregates. Deuterated surfactants and polyelectrolytes will be synthesized for neutron scattering experiments. Teaching and training will be promoted through two curricular development activities benefiting high school students and undergraduates. Understanding the properties of surfactant aggregates is of significant fundamental as well as practical interest. Surfactant aggregates are used widely in personal care products, drug delivery, and a variety of other applications. A long-term goal of this research is to establish a "chemical dictionary" that allows surfactant scientists to understand how bulk properties like viscocity can be manipulated by simple changes in counterion content. In addition, this research has important connections to understanding the impact of counterions on the flexibility of biological molecules such as DNA.