SGER: New Liquid Crystal Materials, Their Phase Behavior, and Transformative Applications

液晶（lc）是由各向异性分子组成的流体，具有一定程度的取向或位置顺序。具有板状或弯核形状的分子，因此，缺乏圆柱对称，产生形成光学双轴向列相和近晶相的可能性。尽管在过去的二十年里进行了大量的研究，但热致双轴向列相一直难以捉摸，直到2004年Kumar等人在弯曲核中质中发现了它。研究人员，大多在美国以外，最近成功地合成了新的和独特的中原，从初步结果来看，这些中原似乎是双轴性研究的绝佳候选者。其中包括几种光敏弯曲核化合物和一类新的材料，称为四足体（具有木板状聚集体形状），由我们在英国，德国和印度的合作者合成。这项由三位跨学科研究人员提出的SGER提案旨在支持使用荧光共聚焦和偏振显微镜，同步加速器x射线衍射和氘核磁共振技术研究这些LC材料的时间紧迫工作，具体目标如下：1)研究具有不同端基的5环、6环刚性本核分子和四足化合物的液晶相性质、结构及其与分子结构的依赖关系；2)确定双轴序参量及其温度依赖性、双轴性对LC相弹性和粘度的影响；3)变革性的电光技术，因为可以在低施加电压下构建更快和多状态的开关设备。所提出的研究结果将引导我们发展一种变革性的显示技术和低成本的器件制造，如可调谐双轴延迟膜。摘要本文提出的研究将通过新的显示技术的出现和这些新材料的其他应用对工业产生巨大的影响。本科生、研究生和博士后将接受物理和化学方面的培训，并引导这些新的双轴LC材料的革命性技术的创造，这些材料有可能改变显示行业的面貌，并影响光子学、电信和网络基础设施领域。初级研究人员将有机会与我们的合作者在其他国家的研究小组成员进行互动和建立长期的专业联系

Liquid crystals (LCs) are fluids, composed of anisotropic molecules, which possess some degree of orientational or positional order. Molecules having a plank-like or bent-core shape and, thus, lacking cylindrical symmetry give rise to the possibility of forming optically biaxial nematic and smectic phases. In spite of vigorous search for the past two decades, the thermotropic biaxial nematic phase had remained elusive until its discovery in 2004 in bent-core mesogens by Kumar, et al. Researchers, mostly outside the US, have recently succeeded in synthesizing new and unique mesogens that, from preliminary results, appear excellent candidates for the study of biaxiality. These include several photosensitive bent-core compounds and a new class of materials, known as the tetrapodes (having plank-like aggregate shape), synthesized by our collaborators in the UK, Germany and India. This SGER proposal by three interdisciplinary researchers seeks support for a time-critical effort to study these LC materials using fluorescence confocal and polarizing microscopy, synchrotron x-ray diffraction, and deuterium NMR techniques, with the following specific objectives: 1) The nature and the structure of liquid crystalphases and their dependence on molecular structure will be studied in the 5- and 6-ring rigid bentcore molecules with different terminal groups and the tetrapodic compounds; 2) The biaxial order parameter, its temperature dependence, the effect of biaxiality on elasticity and viscosities of LC phases will be determined; 3) transformative electro-optics technology due to the possibility of building much faster and multistate switching devices at low applied voltages. Results of the proposed study should lead us to the development of a transformative display technology and low cost fabrication of devices such as tunable biaxial retardation films.Non-technical AbstractThe proposed research will have tremendous impact on industry via the emergence of a new display technology and other applications of these new materials. Undergraduate and graduate students and postdocs will be trained in physics and chemistry, and lead to the creation of a revolutionary technology of these new biaxial LC materials that have the potential of changing the face of display industry and impact the fields of photonics, telecommunications, and cyber infrastructure. Junior researchers will have opportunities to interact and forge long-term professional contacts with members of our collaborators' research groups in other countries