RUI: Thermoreversable hydrogen bonding in mesogenic assembly: enhancing mesogen structure, stability and formation

RUI：介晶组装中的热可逆氢键：增强介晶结构、稳定性和形成

• 批准号: 1808289
• 负责人: Kurt Wiegel
• 金额: $ 26.65万
• 依托单位: University of Wisconsin-Eau Claire
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-08-01 至 2022-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1808289&HistoricalAwards=false
• 关键词: RUI; Thermoreversable; hydrogen; bonding; mesogenic

Non-technical Summary:Liquid crystals (LCs) are in everything that has a digital display: phones, laptops and tablets. They are amongst the most important optically active molecules in the world. Liquid crystalline phases are formed when shaped molecules, called mesogens, align as a liquid. Common wisdom has been that LC phases have a very delicate structure and miniscule amounts of structural or physical defects can destroy it. The ability of a liquid crystalline phase to self-repair or heal would be very significant to understanding how these molecules align under adverse conditions. This project, funded by the Solid State and Materials Chemistry Program in the Division of Materials Research at NSF, investigates new concepts of liquid crystalline networks that are capable of healing and repairing any structural damage that may occur. By changing the type of molecular bonding in the liquid crystal structures, the principle investigator and his group develop a new approach that allows liquid crystal networks to re-form/self-repair, if chemical bonds are broken. Beyond its scientific impact this project enhances the research infrastructure and support human resource development at the University of Wisconsin-Eau Claire. The University of Wisconsin-Eau Claire is a low-cost public institution that has a long-established tradition of strong undergraduate/faculty research collaboration. Almost half of the student body are low-income, first generation students, and about 60% are female, both of which are underrepresented in the scientific communities. This research project greatly enhances student training and intellectual development through hands-on experience with sophisticated equipment and offers the students opportunities to present their findings at national meetings. Technical Summary:The assembly of liquid crystalline materials using non-covalent interactions offers many interesting features involving living polymeric systems and the ability of the mesogens to self-heal and repair macroscale structural defects. Liquid crystalline networks are an area that has received considerable attention due to the ability of the materials to couple the order of the mesogenic directors to the elasticity of the materials. The application of thermoreversible assemblies to liquid crystalline networks is a relatively unexamined area. The ability to combine the healing and reversibility of the hydrogen bond with the characteristics of a crosslinked mesogenic system could produce materials with very intriguing characteristics and properties. This project, funded by the Solid State and Materials Chemistry Program in the Division of Materials Research at NSF, enables the synthesis of a series of liquid crystal precursor networking agents in which the hydrogen bond acceptor is distanced from the central carbon. By varying the functionality of the molecule, the distance from the assembly point to the central carbon (increasing chain length) and the size and rigidity of the hydrogen bond acceptor, the effect of this distal crosslinking on the ability of a hydrogen-bonded liquid crystalline polymer and network to form is investigated. A corollary study determines the effects of using the double hydrogen bond assemblies of the 2-pyridone functionality to create liquid crystalline polymers. In these a series of 2-pyridone aromatic ester tectons are created with variable structure and spacer lengths to determine the effect on mesophase stability and structure, which are studied using spectroscopic, X-ray and thermal analytical techniques. The creation of these new liquid crystalline systems provides valuable insight into the ability of a mesophase to stabilize in unfavorable, constrained (networked) conditions, as well as an understanding of systems assembled through multiple hydrogen bond assemblies. Imparting new characteristics to liquid crystalline systems provides new materials, combining the stabilities of covalent species with the lability and healing capabilities of hydrogen bonded associative chain structures.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.

非技术总结：液晶（LC）存在于所有具有数字显示屏的东西中：手机，笔记本电脑和平板电脑。它们是世界上最重要的光学活性分子之一。当被称为介晶的成型分子排列成液体时，就形成了液晶相。通常认为液晶相具有非常精细的结构，极少量的结构或物理缺陷可以破坏它。液晶相的自我修复或愈合能力对于理解这些分子在不利条件下如何排列非常重要。该项目由NSF材料研究部的固态和材料化学计划资助，研究了能够治愈和修复任何可能发生的结构损伤的液晶网络的新概念。通过改变液晶结构中的分子键合类型，主要研究人员和他的团队开发了一种新方法，如果化学键断裂，该方法允许液晶网络重新形成/自我修复。除了其科学影响，该项目还增强了威斯康星大学欧克莱尔分校的研究基础设施，并支持人力资源开发。威斯康星大学欧克莱尔分校是一所低成本的公立大学，拥有悠久的本科生/教师研究合作传统。几乎一半的学生是低收入的第一代学生，大约60%是女性，这两种人在科学界的代表性不足。这一研究项目通过使用先进设备的实践经验大大加强了学生的培训和智力发展，并为学生提供了在国家会议上介绍其研究结果的机会。使用非共价相互作用的液晶材料的组装提供了许多有趣的特征，涉及活性聚合物系统和介晶自我修复和修复宏观结构缺陷的能力。液晶网络是由于材料将介晶指向矢的顺序与材料的弹性耦合的能力而受到相当大关注的领域。热可逆组装体在液晶网络中的应用是一个相对未被研究的领域。联合收割机将氢键的愈合和可逆性与交联介晶体系的特性结合起来的能力可以产生具有非常有趣的特性和性能的材料。该项目由NSF材料研究部的固态和材料化学计划资助，能够合成一系列液晶前体网络剂，其中氢键受体与中心碳原子保持距离。通过改变分子的官能度、从组装点到中心碳的距离（增加链长）以及氢键受体的尺寸和刚性，研究了这种远端交联对氢键键合的液晶聚合物和网络形成的能力的影响。一个推论的研究确定的影响，使用双氢键组装的2-吡啶酮功能，以创建液晶聚合物。在这些一系列的2-吡啶酮芳族酯tectons创建可变的结构和间隔长度，以确定中间相的稳定性和结构，这是使用光谱，X-射线和热分析技术研究的效果。这些新的液晶系统的创建提供了有价值的洞察能力的中间相，以稳定在不利的，约束（网络）的条件，以及通过多个氢键组件组装系统的理解。赋予液晶系统新的特性，提供新的材料，结合共价物种的稳定性和氢键缔合链结构的不稳定性和愈合能力。该奖项反映了NSF的法定使命，并已被认为是值得支持的评估使用基金会的智力价值和更广泛的影响审查标准。

项目成果

Supramolecular liquid crystals displaying competitive hydrogen bonding: Mesogenic associative chain structures using rigid and flexible pyridyl groups

• DOI: 10.1080/15421406.2019.1685740
• 发表时间: 2019-09
• 期刊: Molecular Crystals and Liquid Crystals
• 影响因子: 0.7
• 作者: E. A. John;Michael D. Heltne;Evan C. Bornowski;David J Lindberg;J. D. Carli;Seth B. Legare;John T. Carli;K. Wiegel