Discotic Liquid Crystals in Nanoporous Solids: From the Structure and Dynamics to Local Charge Transport

盘状液晶镶嵌在纳米多孔固体中是一种非常有趣的杂化材料，涉及到局限分子凝聚态物质的物理和化学基本问题。这些系统对有机电子学也越来越感兴趣。基于我们之前对这些杂化材料的研究结果和专业知识，本项目的主要目标是探索在多大程度上轴向和径向顺序之间的竞争以及一般的相变可以通过改变孔壁分子的锚定条件（表面接枝）、盘状核的大小和/或使用外部磁场来影响。此外，我们打算探索纳米通道中结构的改变、分子/孔壁相互作用的改变以及纳米通道通过形成毛细管桥从膜凝聚态逐渐填充到通道的完全填充对结构、热力学和分子动力学的影响。后者将允许对边界层的厚度进行量化，即受孔壁相互作用强烈影响的孔壁邻近层。为了优化混合系统的实际应用，将考虑的纯盘状液晶进行掺杂，通过共自组装获得电荷转移配合物。对于散装系统，为了优化电输运特性，该策略已被证明是非常成功的。因此，我们打算在受限液晶状态下也探索这种方法。我们的目标将通过结合结构敏感方法（x射线散射、光学双折射测量、差示扫描量热法等）和与分子迁移率相关的实验（介电光谱、比热光谱、中子和准弹性散射）来实现。为了将基础研究与应用联系起来，将尝试使用基于原子力显微镜的方法直接测量（孤立）通道中盘状液晶的局部电导率。该项目将受益于两位提案人的正交专业知识。该项目的成功实现需要两个研究小组之间的密切合作，因为结构决定分子动力学，反之亦然。为了保证这种紧密的合作，将举行联合项目会议，交换博士生进行补充测量和补充培训（除样品交换外）。除了预期的科学成果协同效益外，两位博士生将从这个研究项目的合作精神中获得显著的科学教育收益。

Discotic liquid crystals embedded in nanoporous solids are very interesting hybrid materials with respect to fundamental questions in the physics and chemistry of confined molecular condensed matter. These systems find also increasing interest in organic electronics. Based on the results and expertise gained in our previous studies of these hybrid materials, the main objectives of this project are the exploration to what extent the competition between axial and radial order as well as the phase transitions in general can be influenced by varying the anchoring conditions for the molecules at the pore walls (surface grafting), the size of the discotic cores and/or by employing external magnetic fields. Moreover, we intend to explore how the structure, thermodynamics and molecular dynamics are affected by the resulting changed textures in the nanochannels, by the changed molecule/pore wall interaction and by a gradual filling of the nanochannels from the film-condensed state via the formation of capillary bridges to a complete filling of the channels. The latter will allow for a quantification of the thickness of the boundary layer, that is the layer in the pore wall proximity which is strongly affected by the interaction with the pore walls. To optimize the hybrid systems for real applications the considered pure discotic liquid crystals will be doped to obtain charge-transfer complexes by co-self-assembly. For the bulk systems this strategy has proven as very successful in order to optimize the electric transport properties. Thus, we intend to explore this approach also for the confined liquid crystalline state. Our objectives will be reached by a combination of structure sensitive methods (X-ray scattering, optical birefringence measurements, Differential Scanning Calorimetry etc.) with experiments which are related to the molecular mobility (dielectric spectroscopy, specific heat spectroscopy, in- and quasielastic neutron scattering). To relate the basic research to applications it will be tried to measure the local conductivity of the discotic liquid crystals directly in (isolated) cannels by an AFM-based approach. The project will highly benefit by the orthogonal expertise of both proposers. The successful realization of the project requires an intense cooperation between the two research groups because structure determines the molecular dynamics and vice versa. To warrant this intense cooperation joint project meetings and the exchange of the PhD students for complementary measurements as well as complementary training are plant (additionally to sample exchange). Besides the expected synergistic benefit on the scientific results both PhD students will significantly profit in their scientific education from the cooperative spirit of this research project.