Collaborative Research: Highly ordered concentric multilayer nanostructures with probable liquid crystalline features from rigid sphere-rod amphiphiles in solution

非技术概述在材料研究部固态和材料化学计划以及凝聚态物理计划的支持下，该项目结合了实验、计算研究和教育，旨在促进对刚性嵌段共聚物在液晶溶液中的行为和自组织的基本理解。液晶是介于液体和固体晶体之间的一种物质状态，广泛用作电视屏幕(LCD)、手机和隐形眼镜的显示设备。嵌段共聚物是将两种或两种以上不同的长链聚合物连接在一起形成的。不同的嵌段往往具有不同的溶解性等性质，导致嵌段共聚物自组装成各种纳米结构，成为药物输送、包衣和润滑的重要材料。虽然具有柔性链的嵌段共聚物已经得到了很好的研究，但对于那些具有完全刚性组分的嵌段共聚物却知之甚少。来自阿克伦大学和肯特州立大学的研究人员为每个嵌段设计和研究具有特殊形状的全刚性嵌段共聚物。这一基础研究使研究人员能够了解这些刚性共聚物在溶液中的行为，它们可以自组织成什么类型的超分子结构，以及这些结构的形成是如何受到温度、溶剂以及共聚物的形状和结构的控制的。该团队尤其专注于探索这种刚性嵌段共聚物组件可能出现的液晶特征。该团队通过一系列实验和互补的计算机模拟，研究了一种可能由刚性嵌段共聚物形成的新型液晶及其作为材料的潜在应用。此外，该项目通过阿克伦大学聚合物科学和聚合物工程学院的NSF-REU中心吸引了研究生、本科生和来自俄亥俄州阿克伦-肯特地区的高中生。这笔助学金资助的两所大学的研究生可以通过相互访问、合作实验和讨论来扩大他们的经验。该小组还访问了当地为少数族裔服务的学校，鼓励学生参加科学课程并从事STEM职业。技术总结由材料研究部固体与材料化学项目和凝聚态物理项目支持，阿克伦大学的刘教授和Tsige教授与肯特州立大学的Lavrentovich教授合作，探索完全刚性的球形棒状两亲性嵌段共聚物的自组装。这种刚性共聚物表现出与研究充分的柔性嵌段共聚物完全不同的组装行为，形成了均匀的洋葱状多层同心组装，具有相同的、明确定义的层间距。这些组件通过改变层数来响应溶剂极性、温度和其他因素的变化，同时保持整体结构和层间距离。该项目通过实验表征和计算机模拟相结合的方式实现了以下目标：(1)研究这种新型洋葱状组装的机制和驱动力以及组装尺寸均匀的原因；(2)阐明通过改变溶剂、反离子或温度来合理控制其尺寸(层数)；(3)研究棒长、棒数、球体大小/形状和棒取向对自组装的影响；以及(4)确定这些洋葱状超分子结构是否具有液晶特征，如果具有，这些独特的特征如何影响液晶科学和技术。这项研究扩大了对嵌段共聚材料(从柔性到刚性)和液晶的基本理解，以及它们作为功能材料的潜在应用。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical Summary With support from the Solid State and Materials Chemistry program as well as the Condensed Matter Physics program, both in the Division of Materials Research, this project combines experimental and computational research and education aimed at advancing the fundamental understanding of how rigid block copolymers behave and self-organize in solution to liquid crystals. Liquid crystal is a state of matter between fluid liquids and solid crystals, and broadly used as display devices in TV screens (LCD), cell phones and contact lenses. Block copolymers are formed by linking two or more different long chain polymers together. Different blocks often possess different properties such as solubility, which lead block copolymers to self-organize into various nanometer-scale structures and make them important materials in drug delivery, coating and lubrication. While block copolymers with flexible chains have been well studied, those with fully rigid components are poorly understood. Investigators from the University of Akron and Kent State University design and study fully rigid block copolymers with special shapes for each block. This fundamental investigation enables the researchers to understand how these rigid copolymers behave in solution, what types of supramolecular structures they can self-organize into, and how the structure formations are controlled by temperature, solvent, as well as the shape and architecture of copolymers. The team focuses in particular on exploring the possible liquid crystal features emerging from such rigid block copolymer assemblies. The team examines a probable new type of liquid crystals formed by rigid block copolymers and their potential applications as materials through a series of experiments and complementary computer simulations. Furthermore, the project engages graduate students, undergraduate students through the NSF-REU center at the School of Polymer Science and Polymer Engineering at the University of Akron, and high school students from the Akron-Kent areas in Ohio. Graduate students from both institutions supported by this grant can expand their experience by mutual visits, collaborative experiments and discussions. The team also visits local schools that are serving large numbers of minorities and encourage students to take science courses and pursue careers in STEM.Technical SummarySupported by the Solid State and Materials Chemistry program as well as the Condensed Matter Physics program, both in the Division of Materials Research, Professors Liu and Tsige at University of Akron, along with Professor Lavrentovich at Kent State University, team up to explore the self-assembly of fully rigid, sphere-rod shaped amphiphilic block copolymers. Such rigid copolymers demonstrate completely different assembly behaviors from the well-studied flexible block copolymers, by forming uniform, onion-like, multilayer concentric assemblies with identical, well-defined inter-layer distance. The assemblies respond to the change of solvent polarity, temperature and others by changing the number of layers while maintaining the overall structure and inter-layer distance. The project includes the following objectives which are pursued by combining experimental characterizations and computer simulations: (1) investigation of the mechanism and driving forces of this novel onion-like assembly and the reason for the uniform assembly size; (2) elucidation of the rational control of their size (number of layers) via changing solvent, counterions or temperature; (3) studying the effects of rod length, rod number, sphere size/shape, and rod orientation on the self-assembly, and (4) determination whether these onion-like supramolecular structures possess liquid crystalline features, and if so, how these unique features impact liquid crystal science and technology. The research expands the fundamental understanding of block copolymer materials (from flexible ones to rigid ones) and liquid crystals, as well as their potential applications as functional materials.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.