US Ireland R&D Partnership: Ferroelectric and Electroclinic Effects in Nano-particle Doped de Vries Smectic Liquid Crystals: Molecular Organisation and Order

非技术摘要：目前用于平板显示器的液晶技术已经达到了切换速度和对比度的极限，不能满足下一代高性能显示器的要求。两种相对较新、研究较少的液晶开关现象被称为电倾斜效应和铁电效应，它们有望比目前的液晶显示器快1000倍以上的开关速度和更高的对比度。在材料研究部固态和材料化学计划的支持下，这个隶属于美国国家科学基金会美国爱尔兰研发伙伴计划的跨学科研究团队致力于设计和合成优化这些开关现象的新液晶分子，研究这些材料的分子组织和对外加电场的响应，调查不同形状和大小的溶解纳米粒子在提高其性能方面的作用，并开发基于这两种变革性技术的制造概念验证显示单元的协议和工艺。该项目汇集了来自美国、爱尔兰和北爱尔兰的研究生以及初级和高级研究人员，并为他们提供了合作的机会，并获得了任何一个实验室都无法获得的各种技术技能。该项目在高级光子源(阿贡国家实验室)和国家同步加速器光源(布鲁克海文国家实验室)对学生进行尖端实验和分析技术方面的教育，如微拉曼散射、专门的光学方法和高分辨率同步加速器X射线研究。肯特州立大学和(两年制)斯塔克州立学院的本科生在暑假期间参与研究活动，在当地学校进行科学演示，以及K-12学生参观实验室，这些都是该项目的关键教育组成部分。技术摘要：De Vries近晶液晶表现出可以忽略不计的热膨胀，因此为其铁电和电临床性质的技术应用提供了一条重要且可能是唯一的途径。这个美国爱尔兰研发伙伴项目致力于了解显著的热特性、电倾斜效应和铁电效应背后的现象，以及它们对分子结构的依赖，并开发设备应用所需的基本表面对准协议。该研究小组计划合成和研究具有不同比例的硅氧烷与烃类链段、手性中心和具有烃类末端链段的全氟化分子的分子，以获得从分子结构预测其行为的能力。这是使用最先进的实验技术实现的，如同步辐射X射线衍射、拉曼和红外散射以及宽带介电光谱。取向有序参数、取向分布函数、指向倾斜有序参数和近晶有序参数的确定对于确定扩散锥和糖饼哪个理论模型是有效的至关重要。计划在液晶中掺杂纳米粒子、-棒和-盘，以改善响应时间、阈值电压和对比度。项目组计划全面了解这些系统，并展示用于显示、光通信和传感器应用的新一代电诊所和铁电液晶设备的概念验证。

Non-Technical Abstract:The liquid crystal technology currently used in flat panel displays has reached the limits of switching speed and contrast ratio, and cannot meet the requirements of next generation of high-performance displays. Two relatively new and less studied liquid crystal switching phenomena, known as the electroclinic and ferroelectric effects, hold the promise of more than a thousand times faster switching speeds and much higher contrast than the present liquid crystal displays. With support from the Solid State and Materials Chemistry Program in the Division of Materials Research, this interdisciplinary research team under the US Ireland R&D Partnership program of the National Science Foundation seeks to design and synthesize new liquid crystal molecules that optimize these switching phenomena, study the molecular organization and response of these materials to applied electric fields, investigate the role of dissolved nano-particles of different shapes and sizes in improving their performance, and develop protocols and processes leading to the fabrication of proof-of-concept display cells based on these two transformative technologies. The project brings together graduate students, and junior and senior researchers from the US, Ireland, and Northern Ireland and provides them with opportunities to collaborate and acquire diverse sets of technical skills not available in any one laboratory. The project educates students in cutting edge experimental and analytical techniques such as micro-Raman scattering, specialized optical methods, and high-resolution synchrotron x-ray studies at the Advanced Photon Source (Argonne National Laboratory) and the National Synchrotron Light Source (Brookhaven National Laboratory). Participation in research activities during summer by undergraduate students at Kent State University and from (two-year) Stark State College, science demonstrations at local schools, and laboratory visits by K-12 students are among the key educational components of the project. Technical Abstract:de Vries smectic liquid crystals exhibit negligible thermal expansion and hence offer an important and perhaps the only pathway to technological applications of their ferroelectric and electroclinic properties. This US Ireland R&D Partnership project strives to understand the phenomena underlying the remarkable thermal characteristics, the electroclinic and ferroelectric effects, their dependence on molecular structure, and to develop the essential surface alignment protocols required for device applications. The research team plans to synthesize and study molecules with different ratios of siloxane to hydrocarbon segments, chiral centers, and per fluorinated molecules with a hydrocarbon end-segment to acquire the ability to predict their behavior from molecular structure. This is achieved using state-of-the-art experimental techniques such as synchrotron X-ray diffraction, Raman and IR scattering, and wideband dielectric spectroscopy. Determination of the orientational order parameters, orientational distribution function, director tilt order parameter, and smectic order parameter are critical in resolving which of the theoretical models, diffuse cone or sugarloaf, is valid. Doping of liquid crystals with nano-particles, -rods, and -discs is planned to improve the response time, threshold voltage, and contrast ratio. The project team plans to acquire a comprehensive understanding of these systems and demonstrate proof-of-concept new generation electroclinic and ferroelectric liquid crystal devices for displays, optical communications, and sensor applications.