Filled Polar Liquid Crystals from Umbrella-Shaped Mesogens

在这个工作组（WG） Lehmann （w<s:1> rzburg）和Eremin （Magdeburg）之间的合作项目中，我们建议设计和探索以其固有极性特性为特征的新型半导体液晶材料。由WG Lehmann进行的设计是基于合成具有亚酞菁核心和共轭臂（oligothiophenes, benzothienobenzothiophenes, thienylpyrrolopyrrothiophenes）的星形中间原，并以脂肪链装饰。后者诱导柱状液晶（LC）相。这种半导体介原形成极性相，因此在薄的排列薄膜中会产生反常的光伏效应。在这个项目中，我们打算探索这些材料的结构、光学、电子和极性特性，并优化它们用于透视设备的应用。合成和纯化后，将在溶液和薄膜中研究其光物理性质。将使用偏光显微镜、差示扫描量热法、x射线散射（WAXS、SAXS、GISAXS）和Materials Studio软件建模来研究中间相的热致性行为和结构。通过表面处理，退火和磁场和电场的使用，将优化对准。利用宽带介电光谱和光二次谐波的产生，我们将探索新材料的极性性质。反常光伏效应将在薄取向的极性薄膜中进行测试。这种材料应该表现出光电流，而不需要供体-受体（p/n）结。这些结构性质研究的结果将用于进一步优化分子设计。WG Lehmann将制备星型中介原衍生物，其共轭臂通过具有不同间隔长度的柔性间隔连接到富勒烯（C60）上。这些分子在空间上过于拥挤，不能形成LC相。不含富勒烯的原始恒星中旋原在旋臂之间具有固有的自由空间，可以承载C60。因此，这些分子与空间过度拥挤的富勒烯衍生物之间的混合物产生了新的、极性的、高度有序的柱状给体-受体LC相。这些“富勒烯填充”的液晶是一种新型的供体-受体材料，可以控制电极之间的形态和排列。极性性质有利于电荷分离。“填充”的中间相将被研究其结构-性质关系，即软物质（lc和软晶体）中的自组装，光物理和极性性质，排列，载流子迁移率和光伏性质。因此，WGs Lehmann和Eremin的联合多学科项目将导致新一代液晶，极性半导体材料，可以同向异性排列，从而允许在有机光伏中的应用。

In this collaborative project between the workgroups (WG) Lehmann (Würzburg) and Eremin (Magdeburg), we propose to design and explore novel semiconducting liquid crystalline materials distinguished by their intrinsic polar properties. The design conducted by the WG Lehmann is based on the synthesis of star-shaped mesogens with a subphthalocyanine core and conjugated arms (oligothiophenes, benzothienobenzothiophenes, thienylpyrrolopyrrolthiophenes) decorated with aliphatic chains. The latter induce columnar liquid-crystalline (LC) phases. Such semiconducting mesogens form polar phases, for which an anomalous photovoltaic effect in thin, aligned films is expected. In this project, we intend to explore the structural, optical, and electronic and polar properties of these materials as well as to optimise them for perspective device applications. After synthesis and purification, the photophysical properties will be studied in solutions and thin films. The thermotropic behaviour and the structure of the mesophases will be investigated using polarised optical microscopy, differential scanning calorimetry, X-ray scattering (WAXS, SAXS, GISAXS) and the modelling with the Materials Studio software. The alignment will be optimised by surface treatment, annealing and usage of magnetic and electric fields. Using broadband dielectric spectroscopy and optical second-harmonic generation, we shall explore the polar properties of the new materials. The anomalous photovoltaic effect will be tested in thin oriented, polar films. Such materials should exhibit a photocurrent without the need of a donor-acceptor (p/n) junction. The output of these structure-property studies will be used for further optimisation of the molecular design. The WG Lehmann will prepare star mesogen derivatives, for which the conjugated arms are tethered to fullerenes (C60) via flexible spacers with different spacer lengths. These molecules are sterically overcrowded and do not form LC phases. The original star mesogens without fullerenes possess between their arms intrinsic free space, which can host C60. Consequently, the mixture between these molecules with the sterically overcrowded fullerene derivatives results in new, polar, highly ordered, columnar donor-acceptor LC phases. These "fullerene-filled" liquid crystals are novel donor-acceptor materials, which allow the control of the morphology and the alignment between electrodes. The polar properties will facilitate charge separation. The "filled" mesophases will be investigated for their structure-property relationships, i.e. the self-assembly in soft matter (LCs and soft crystals), photophysical and polar properties, alignment, charge-carrier mobilities, and photovoltaic properties.Thus, the joint, multidisciplinary project of the WGs Lehmann and Eremin will result in a new generation of liquid-crystalline, polar semiconductor materials, which can be homeotropically aligned and thus, allow the application in organic photovoltaics.