From Molecular Simplicity to Supramolecular Complexity: Low Symmetry Packings of Ionic Spherical Micelles

表面活性剂是一种小分子，其中一个水溶性的头基团附着在一个不可溶的尾基团上。常用的表面活性剂有肥皂和洗涤剂。由于头基和尾基的溶解度不同，表面活性剂在水中会自发地形成有序的组合。这些组件可以从非常简单的分散在水中的球体到更复杂的几何形状。然而，从表面活性剂的化学结构预测复杂组装体的几何形状仍然是一个重大挑战。明尼苏达大学双城分校的Mahesh Mahanthappa教授和他的研究小组希望控制表面活性剂的组装，并获得具有不同寻常和有用性质的复杂结构，他们试图了解表面活性剂的结构如何决定填料的几何形状和组装的稳定性。他们的发现可能会对未来表面活性剂的设计和开发产生广泛的影响，如提高石油采收率，个人护理产品配方，药物封装和治疗递送。该项目还有助于本科生和研究生，包括代表性不足群体成员的跨学科研究培训。利用具有视觉吸引力的肥皂泡，向公众展示表面活性剂的特性，并有助于激发学生对科学的兴趣。非共价相互作用的微妙平衡驱动最低水合两亲体的超分子组装成不同的冻养液晶相。特别令人感兴趣的是复杂的Frank-Kasper （FK）相，它显然是由一种受挫的非共价力平衡引起的，这种平衡最小化了两亲溶剂化的局部变化，同时最大化了整个超分子组装的整体胶束内聚。本项目的具体实验旨在：1)了解离子两亲体的尾部结构、反离子对称性和手性如何影响胶束的聚集，以及胶束随后堆积成高配位数、低对称晶格；2)评价这些复合填料是长寿命的亚稳态还是热力学平衡相；3)评估非离子型两亲体是否可能形成这些络合相。一个重要的目标是揭示新的分子设计标准，驱动具有特殊平移顺序的溶致液晶的形成，其长度尺度远远超过其组成分子和超分子胶束构建块。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Surfactants are small molecules in which a water-soluble headgroup is attached to an insoluble tail. Common examples of useful surfactants are soaps and detergents. As a result of the different solubilities of the headgroup and the tail, surfactants spontaneously form ordered assemblies in water. The assemblies can range from very simple spheres dispersed in water to much more sophisticated geometries. However, predicting the geometry of a complex assembly from the chemical structure of the surfactant remains a significant challenge. Motivated by the desire to control surfactant assembly and access complex structures with unusual and useful properties, Prof. Mahesh Mahanthappa and his research team at the University of Minnesota-Twin Cities seek to understand how surfactant structure dictates the packing geometry and the stability of an assembly. Their discoveries could have broad implications for the future design and development of surfactants for applications such as enhanced oil recovery, personal care product formulation, drug encapsulation, and therapeutic delivery. The project also contributes to the interdisciplinary research training of undergraduate and graduate students, including members of underrepresented groups. Public outreach demonstrations using visually appealing soap bubble froths showcase the properties of surfactants and help to arouse the interest of students in science.A delicate balance of non-covalent interactions drives the supramolecular assembly of minimally hydrated amphiphiles into different lyotrophic liquid-crystalline phases. Of particular interest is the complex Frank-Kasper (FK) phases, which apparently arise from a frustrated non-covalent force balance that minimizes local variations in amphiphile solvation, while maximizing global micelle cohesion across the supramolecular assembly. Specific experiments of this project aim to 1) understand how the ionic amphiphile tail structure, counterion symmetry, and chirality impact micellar aggregation and consequent packing of the micelles into high coordination number, low symmetry lattices; 2) evaluate whether these complex packings are long-lived metastable states or thermodynamic equilibrium phases; and 3) assess whether non-ionic amphiphiles might form these complex phases. An important goal is to uncover new molecular design criteria that drive the formation of lyotropic liquid crystals with exceptional translational order, at length scales far exceeding those of their constituent molecular and supramolecular micelle building blocks.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.