Phase Behavior and Physical Properties of Thermotropic and Lyotropic Liquid Crystal Oligomers

热致液晶低聚物和溶致液晶低聚物的相行为和物理性质

基本信息

批准号：
1904167
负责人：
Samuel Sprunt
金额：
$ 57.31万
依托单位：
Kent State University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2019
资助国家：
美国
起止时间：
2019-07-15 至 2023-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1904167&HistoricalAwards=false
关键词：
Phase Behavior Physical Properties Thermotropic

项目摘要

Non-technical Abstract:Liquid crystals are best known for their use in information displays like smartphone screens and flat-panel televisions. They are also a fascinating state of matter whose fundamental understanding and technological potential continue to pose interesting challenges and opportunities. While much is known about what kinds of molecules or molecular assemblies tend to form liquid crystals, there are important open questions about how the specific architecture of these constituents determines the nature and properties of the liquid crystalline states they exhibit. This project explores liquid crystalline states formed by "oligomers" that are constructed by connecting together a small number of elongated, rigid components via flexible linkages. One thrust of the project focuses on oligomers composed of short, rigid segments of double-stranded DNA (duplex DNA) linked by flexible, single strands. Here the objective is to elucidate the liquid crystalline states formed in concentrated aqueous solutions of these constructs, including layered structures that are not observed in solutions of fully paired duplexes and that may offer a new means to simulate crowded DNA (physiological) environments. A second thrust investigates the liquid crystalline properties of much smaller "rigid+flexible" oligomers built up from molecules similar to the types used in displays. These materials afford new possibilities to tune certain viscoelastic properties, which could improve existing liquid crystal devices or motivate entirely new ones. The parallel study of the two oligomeric systems with similar architectures expressed on different microscopic length scales should enhance insights into how these architectures determine macroscopic material properties. The project trains students at graduate and undergraduate levels, across disciplines (physics, biochemistry, materials science), for productive careers in the 21st century scientific workforce. The students have ample opportunities to master a broad spectrum of experimental techniques both in the "benchtop" laboratory setting and at large US national laboratories.Technical Abstract:This project experimentally investigates two distinct molecular systems where linking a small number of rigid subunits with flexible connectors promotes new liquid crystalline (LC) phase behavior or significantly alters macroscopic physical properties of familiar LC phases. Thermotropic LC oligomers consist of two or more small, rigid molecular elements connected by flexible spacers, whose specific arrangement can favor bent or helical conformations. These oligomers undergo transitions between LC states driven primarily by changes in enthalpy. Lyotropic, nucleic acid-based LCs, composed of DNA duplexes linked by single-stranded "gaps" or containing extra, unpaired base inclusions ("kinks"), also possess a "rigid+flexible" oligomer-like architecture, at ~10 times the length scale of the thermotropic materials. The DNA constructs exhibit concentration-dependent mesophases influenced primarily by entropy. The major objectives of the project are: (1) To measure orientational viscoelastic parameters of thermotropic LC oligomers, with emphasis on extending the results from dimers to higher n-mers, and to correlate their relative magnitudes and temperature dependencies with the nature of nanoscale modulated phases, such as the "twist-bend" phase, these oligomers form; (2) To examine the orientational anchoring of oligomers at the free surfaces of LC droplets and quasi-two-dimensional, freestanding LC films drawn from n-mer/monomer mixtures; (3) To determine the structure of mesophases exhibited in concentrated solutions of DNA duplexes that form oligomer-like constructs due to the selective placement of "gaps" and "kinks"; and (4) To explore, selectively, certain potential technological applications in areas ranging from responsive optical devices to new approaches for simulating crowded, physiological DNA environments to a concept for viral DNA/RNA detection. Experiments are performed in the PI and co-PIs' laboratories and at US National Labs, and utilize techniques including laser light scattering, small- and wide-angle X-ray scattering, high sensitivity fluorescence detection, magneto-optics in high fields, and "click chemistry" methods to assemble the DNA constructs.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.

非技术摘要：液晶以其在智能手机屏幕和平板电视等信息显示中的使用而闻名。它们也是一种令人着迷的问题，其基本理解和技术潜力继续构成有趣的挑战和机遇。尽管对哪种分子或分子组件倾向于形成液晶的众所周知，但关于这些成分的特定结构如何决定它们所展示的液体晶体状态的性质和特性，存在重要的开放问题。该项目探讨了由“低聚物”形成的液晶状态，这些状态是通过通过柔性链接将少量伸长的刚性组件连接在一起而构建的。该项目的一个推力重点是由柔性单链连接的双链DNA（双链DNA）的简短片段组成的低聚物。这里的目的是阐明这些构建体的浓缩水溶液中形成的液晶状态，包括在完全配对的双链体溶液中未观察到的分层结构，并可能提供一种新的手段来模拟拥挤的DNA（生理）环境。第二个推力研究了较小的“刚性+柔性”低聚物的液晶特性，该低聚物是由类似于显示中使用类型的分子而建立的。这些材料提供了一些新的可能性来调整某些粘弹性特性，从而可以改善现有的液晶设备或激励全新的液晶设备。在不同的微观长度尺度上表达的两个寡聚系统的平行研究应增强对这些结构如何确定宏观材料特性的见解。该项目将跨学科（物理，生物化学，材料科学）的毕业生和本科阶段的学生培训学生在21世纪的科学劳动力中培训学生。这些学生有足够的机会在“台式”实验室环境和大型美国国家实验室中掌握广泛的实验技术。技术摘要：该项目实验研究了两个不同的分子系统，其中将少量的刚性亚基与灵活的连接器联系起来促进新的液晶（LC）相行为，或显着改变熟悉的LC相的宏观物理特性。热液LC低聚物由两个或更多小的刚性分子元素组成，这些分子元素由柔性垫片连接，其特定排列可以有利于弯曲或螺旋构象。这些低聚物在LC状态之间进行过渡，主要是焓变动。 lyotropic，基于核酸的LCS，由单链“ Gaps”连接的DNA双链体组成，或包含额外的，未配对的碱基夹杂物（“ kinks”），也具有“刚性+柔性”寡聚的构建，在〜10次热型材料的长度尺度。 DNA构建体表现出主要受熵影响的浓度依赖性中间酶。该项目的主要目的是：（1）测量热型LC低聚物的定向粘弹性参数，重点是将二聚体的结果扩展到较高的N-Mers，并将其相对幅度和温度依赖性与纳米级调制的性质相关这些阶段，例如“扭曲”阶段，这些低聚物形成；（2）检查在LC液滴的自由表面和准二维的自由表面上的定向锚定，从N-MER/MONEMER混合物中绘制的独立式LC膜；（3）确定由于选择性放置“ Gaps”和“ Kinks”的选择性放置，在DNA双链体的浓缩溶液中表现出的中间酶的结构；（4）在有选择地探索从响应式光学设备到模拟拥挤的生理DNA环境再到病毒DNA/RNA检测概念的新方法的领域中的某些潜在技术应用。实验是在PI和Co-Pis的实验室和美国国家实验室中进行的，并利用包括激光光散射，小角度和广角X射线散射，高灵敏度荧光检测，高场中的磁极磁性以及“点击化学”方法来组装DNA结构。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛影响的评论标准来评估的。