Dipolar Molecular Rotors in Surface and Bulk Inclusion Compounds.

该项目旨在构建一类新的材料，“旋转电子”，其中晶体材料，通常被认为是由刚性结合的原子组成，也包含自由旋转的分子成分。特别令人感兴趣的是旋转部件携带永久电偶极矩的情况。这些材料早就被预测到，但似乎不存在于自然界中，并提供了一个学习如何通过设计构建新的和潜在有用材料的机会。旋转电相是铁电相的特殊例子，铁电相在记忆棒、手机高频滤波器和显示器中控制光偏振等领域都有应用。旋转电机提供了使这些元件小型化并使其运行更快的机会。该项目支持一名研究生的教育，该研究生在偶极材料设计、各种实验光谱学技术和基础材料理论方面接受博士水平的培训。该项目希望让代表性不足的少数民族参与纳米工程研究。通过将研究成果整合到材料科学和工程课程中，进一步利用纳米尺度建模和实验方面的未来工程师培训。项目成果和材料设计见解通过物理、工程和教育网站进一步传播。技术摘要：研究小组利用主/客分子工程方法构建了几乎自由旋转的偶极分子的晶体阵列。目前的宿主系统是晶体、薄膜和有充分文献记载的三（邻苯二氧基）环三磷腈（TPP）材料的结晶粉末，它形成一个六边形结构，具有沿六边形c轴方向的开放通道。已知这些通道可以接受各种各样的客体分子。该团队研究了放置特殊合成的偶极分子所产生的介电相，这些分子经过专门设计，可以使偶极组分在TPP通道（三维材料）或TPP表面（二维材料）中几乎自由旋转。这些化合物的研究结合了射频介电光谱、x射线衍射、固态核磁共振光谱、体和微拉曼光谱，以及原子力显微镜对表面定位和薄膜材料的研究。其他探针，特别是中子衍射和尖端增强拉曼通过合作研究。新的旋转电材料预计具有远低于传统铁电材料传播速度的铁电波，例如，允许小型化表面声波器件。这项研究有助于组装几乎自由旋转的分子组分的分子系统，并在这类材料中证明有序的介电相。该项目致力于为物质的偶极相的构建提供新的见解，并有可能提供新的有用材料。

Non-Technical AbstractThis project aims to construct a new class of materials, "roto-electrics", in which crystalline materials, normally thought of as composed of rigidly bound atoms, also contain molecular components that are free to rotate. Of particular interest are cases where the rotating components carry a permanent electric dipole moment. These materials have long been predicted but appear not to exist in nature and provide an opportunity to learn how to build new and potentially useful materials by design. Roto-electric phases are special examples of ferroelectric phases and ferroelectrics find application in such areas as memory sticks, high frequency filters in cell phones, and for controlling light polarization in displays. Roto-electrics offer the opportunity to miniaturize such components and to make them operate faster. The project supports the education of a graduate student, who receives Ph.D.-level training in the design of dipolar materials, in a wide variety of experimental spectroscopy techniques, and in the underlying materials theory. The project looks to involve under-represented minorities in nano-engineering research. It further leverages the training of future engineers in both nano-scale modeling and experiment, by the integrating the research results into materials science and engineering curricula. Project results and materials design insights are further distributed through physics, engineering, and educational websites.Technical AbstractThe research team builds crystalline arrays of nearly-freely rotating dipolar molecules with a host / guest molecular-engineering approach. The present host systems are crystals, thin-films, and crystalline powders of the well-documented tris (o-phenylenedioxy) cyclotriphosphazene (TPP) material, which forms a hexagonal structure with open channels directed along the hexagonal c-axis. The channels are known to accept a large variety of guest molecules. The team investigates the dielectric phases that result from placing specially synthesized dipolar molecules, specifically designed to allow for nearly free rotation of the dipolar components, in the bulk of the TPP channels (3-dimensional materials) or at TPP surfaces (2-dimensional materials). These compounds are studied using a combination of radio-frequency dielectric spectroscopy, x-ray diffraction, solid-state nuclear magnetic resonance spectroscopy, bulk and micro-Raman spectroscopy, and, for surface-localized and thin-film materials, with atomic force microscopy. Other probes, especially neutron diffraction and tip-enhanced Raman are investigated via collaborations. The new roto-electric materials are predicted to have ferroelectric waves that propagate at speeds far below those of traditional ferroelectrics, allowing e.g., for miniaturized surface acoustic wave devices. This research makes contributions to the assembly of molecular systems of nearly-freely rotating molecular components, and in demonstrating ordered dielectric phases in such materials. The project works to provide new insights into the construction of dipolar phases of matter, and has the potential to provide new useful materials.