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

田纳西大学诺克斯维尔的琳达马吉德是由实验物理化学计划的研究，重点是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宏观性质（如粘度，去污力和润湿性）的解决方案。 表面活性剂在水溶液中自组装以形成具有各种分子形状的聚集体，包括球体、延伸的蠕虫状结构、蠕虫和囊泡的分支网络以及双层结构。 离子表面活性剂聚集体携带净电荷，并与常规聚电解质具有多种相似性。 本研究的核心是通过改变表面活性剂离子的化学结构来调整聚集体结构的技术。 特别强调的是放在理解哪些结构特征导致聚合分支，并导致蠕虫状结构收缩回球体。 散射方法（光，X射线和中子），显微镜和核磁共振光谱将被用来研究聚集体的微观结构和动力学。 氘代表面活性剂和聚电解质将被合成用于中子散射实验。 将通过两项使高中生和大学生受益的课程编制活动促进教学和培训。了解表面活性剂聚集体的性质具有重要的基础和实际意义。 表面活性剂聚集体广泛用于个人护理产品、药物递送和各种其它应用中。 这项研究的一个长期目标是建立一个“化学词典”，使表面活性剂科学家能够理解如何通过简单的改变表面活性剂含量来操纵粘度等本体性质。 此外，这项研究与理解抗衡离子对DNA等生物分子灵活性的影响有重要联系。

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.