Structured Fluids from Reduced Symmetry Molecules

技术总结肯特州立大学的a . Jákli、J.T. Gleeson和S. Sprunt组成的研究小组最近的研究清楚地表明，由“弯核”（或“香蕉”形）分子构成的液体与由棒状材料构成的液体表现出明显不同的特性；例子包括异常流动粘度和巨大的机电耦合，后者在分子尺度的能量转换应用中具有很高的技术前景。这些材料显然还具有纳米尺度的复杂结构，并表现出物质新状态的迹象。为了全面了解这些结构，肯特州立小组将利用一系列强有力的精心定位的实验技术，这些技术可以在内部获得，也可以通过积极参与国家用户设施。有待研究的特定新型非对称材料包括W、T、X和h型分子，基于弯核分子的令人兴奋的新型聚合物流体和凝胶，以及以前未研究过的低分子量弯核分子。本研究的具体研究目标和科学效益是：(1)对弯核流体的纳米结构进行具体阐明；(2)研究电性质和机械变形之间异常大耦合的起源和限制(3)研究形成新型三维结构的强不对称弯核分子；(4)研究了含弯核亚基的主链和侧链聚合物的光学和机电性能；(5)研究强磁场下的结构流体，寻找场致对称性破缺跃迁。结构流体不仅具有基本的科学意义，而且具有巨大的技术重要性。也许最熟悉的例子是液晶，其应用范围从iPod屏幕到防弹背心。决定结构流体物理行为的关键因素是分子组分的对称性。肯特州立大学的A. Jákli、J.T. Gleeson和S. Sprunt团队将研究的化合物，其结构单元不是传统液晶中的简单棒状结构，而是弯曲型、W型、T型、X型和H型。底层分子形状的对称变化可以导致由这些分子组成的流体的显著不同和技术上有前途的行为。该项目提供了重大技术进步的希望，例如基于增强机电耦合的低成本，可穿戴（或潜在的生物植入）发电机和新一代快速，低功耗反射彩色显示器。拟议的研究将为合成化学家改善材料性能提供关键反馈；这项工作的主要合作者包括教授。R. Twieg（肯特州立大学化学系）和R. Verduzco（莱斯大学化学工程系）。该团队的多方面教育计划将培养博士生成为21世纪创业环境中的有效参与者。主要研究人员还将把本科生，特别是来自传统上代表性不足的群体的大学的本科生，带入一个前沿的研究环境，目标是增加他们对未来高科技劳动力的参与。固态和材料化学项目的支持得到了认可。

TECHNICAL SUMMARYRecent studies of a team by A. Jákli, J.T. Gleeson and S. Sprunt at Kent State University have clearly demonstrated that fluids built from "bent-core" (or "banana" -shaped) molecules exhibit strikingly different properties from those composed of rod-shape materials; examples include anomalous flow viscosity and giant electro-mechanical coupling the latter being of high technological promise for molecular-scale energy conversion applications. These materials also apparently possess complex structure on the nanometer scale, and exhibit indications of novel states of matter. To develop a complete comprehension of these structures, the Kent State Group will utilize a powerful range of carefully targeted experimental techniques, available in house or through active participation in national user facilities. Specific new classes of reduced-symmetry materials to be investigated include molecules having W, T, X and H-shape, exciting new polymeric fluids and gels based on bent-core molecules, as well as previously uninvestigated low molecular weight bent-core molecules. The specific research objectives and scientific benefits of the proposed research are: (1) specific elucidation of nanoscopic structure in bent-core fluids; (2) investigation into the origins and limits of anomalously large coupling between electric properties and mechanical deformation (3) studies of strongly asymmetric bent-core molecules that form novel three-dimensional structures; (4) investigation of the optical and electro-mechanical properties of main- and side- chain polymers containing bent-core sub-units; and (5) studies of structured fluids under high magnetic fields to search for field-induced symmetry breaking transitions.NON-TECHNICAL SUMMARYStructured fluids are not only of fundamental scientific interest but have also enormous technological importance. Perhaps the most familiar example is liquid crystals, whose applications range from iPod screens to bullet-proof vests. The key factor determining the physical behavior of structured fluids is the symmetry properties of the molecular constituents. The team of A. Jákli, J.T. Gleeson and S. Sprunt at Kent State University will study compounds whose building blocks are not simple rods as in traditional liquid crystals, but either bent-shape, W, T, X and H shaped. A symmetry change in underlying molecule shape can lead to dramatically different and technologically promising behavior of a fluid composed of such molecules. This project offers the promise of significant advances in technology, such as low-cost, wearable (or potentially bio-implantable) electricity generators based on enhanced electro-mechanical coupling and a new generation of fast, low-power reflective color displays. The proposed research will provide critical feedback for synthetic chemists to improve material properties; key collaborators in this effort include Profs. R. Twieg (Department of Chemistry, Kent State University) and R. Verduzco (Department of Chemical Engineering, Rice University). The team's multi-faceted education program will train doctoral students to be effective players in a twenty-first century entrepreneurial environment. The principal investigators also will bring undergraduates, particularly from colleges serving traditionally under-represented groups, into a cutting-edge research environment, with the goal of increasing their participation in the high-tech workforce of tomorrow.Support from the Solid State and Materials Chemistry program is acknowledged.