Materials World Network: Structure, Dynamics and Critical Phenomena in Biaxial Liquid Crystals

英国船体大学和肯特州立大学的科学家之间的这一国际合作具有互补的专业知识，重点是理解与双轴性相关的现象-两个不同光轴的自发发生-在所谓的液晶（LC）的双相。虽然这是假设约38年前，双轴向列，直到最近，证明相当难以捉摸的真实的材料-事实上，几乎所有的向列是光学单轴和几乎所有的应用LC已被限制到一个单一的光轴的操纵。双轴取向相预期在由形状上固有双轴的分子（或分子聚集体）组成的LC中，例如，香蕉状或香蕉核（香蕉形）分子。另一个重要的可能性，形成一个双轴向的，这一直是几个激烈的理论研究的主题，出现在混合物的盘形和棒状分子。取决于这些组分分子的纵横比和浓度，可以预期三个双轴相，两个单轴相和一个双轴相，具有相图的特定拓扑结构和相变性质的有趣演变。英国的首席研究员Georg Mehl教授和他的团队开创了相容的棒状和盘状系统的合成，这些系统形成稳定的溶液并表现出不同的双相（可能包括双轴相）。美国研究人员将探索双轴分子系统和棒-盘混合物系统中不同液晶相之间几个有趣相变的结构、光学和其他物理性质、动力学和临界行为，其结果和获得的数据将有助于检验现有理论的有效性，并为新型液晶材料的物理和化学提供重要见解。研究人员将采用最先进的技术，如动态光散射，同步加速器x射线衍射，共聚焦和原子力显微镜，以及电光测量在他们的调查。该项目的结果可能会通过一种新的显示技术的出现和光学双轴流体的其他应用对行业产生变革性的影响。本科生、研究生和博士后将在一个有可能影响光子学、电信和网络基础设施领域的领域接受培训。初级研究人员将有机会与英国研究小组成员和高级光子源的其他国际学者进行互动并建立长期的专业联系。美国研究生和博士后将能够多样化他们的技能和科学经验，并在开始他们的职业生涯时对材料开发和物理表征有深刻的认识。

This international collaboration, between scientists at the University of Hull, UK and Kent State University having complementary expertise, focuses on understanding phenomena associated with biaxiality - the spontaneous occurrence of two distinct optical axes - in the so-called nematic phase of liquid crystals (LCs). Although it was hypothesized about 38 years ago, biaxial nematics have, until recently, proven quite elusive in real materials - indeed, virtually all nematics are optically uniaxial and virtually all applications of LCs have been restricted to the manipulation of a single optical axis. The biaxial nematic phase is expected in LCs composed of molecules (or, molecular aggregates) that are intrinsically biaxial in shape, e.g., plank-like or bent-core (banana-shaped) molecules. Another important possibility for formation of a biaxial nematic, which has been the subject of several intense theoretical investigations, arises in mixtures of disk- and rod-shaped molecules. Depending on the aspect ratios of these component molecules and on the concentration, one can expect three nematic phases, two uniaxial and one biaxial, with a specific topology of the phase diagram and interesting evolution of the nature of phase transitions. The principal investigator in the UK, Professor Georg Mehl, and his team have pioneered the synthesis of compatible rod- and disk-like systems, which form stable solutions and exhibit distinct nematic phases (possibly including a biaxial phase). The US researchers will probe the structure, optical, and other physical properties, the dynamics, and critical behavior at several interesting phase transitions between different nematic phases, both in systems with biaxial-shaped molecules and in rod-disc mixtures.The results and the data acquired under this project will help test the validity of the current theories and provide important insight into the physics and chemistry of novel LC materials. The researchers will employ state-of-the-art techniques such as dynamic light scattering, synchrotron x-ray diffraction, confocal and atomic force microscopies, and electro-optical measurements in their investigations. The results of this project are likely to have transformative impact on the industry via the emergence of a new display technology and other applications of optically biaxial fluids. Undergraduate and graduate students and postdocs will be trained in an area that has the potential of impacting the fields of photonics, telecommunications, and cyber infrastructure. Junior researchers will have opportunities to interact and forge long-term professional contacts with members of the research group in the UK and other international scholars at the Advanced Photon Source. US graduate students and postdocs will be able to diversify their skills and scientific experience and begin their careers with a profound appreciation for materials development as well as physical characterization.