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

嵌在纳米多孔固体中的离散液晶是一种非常有趣的杂化材料，它涉及到受限分子凝聚态物理和化学的基本问题。这些系统在有机电子学中也引起了越来越多的兴趣。基于我们以前对这些混合材料的研究中获得的结果和专业知识，该项目的主要目标是探索轴向和径向顺序之间的竞争以及一般的相变在多大程度上可以通过改变孔壁分子的锚定条件（表面接枝），分散核的大小和/或通过采用外部磁场来影响。此外，我们打算探索如何的结构，热力学和分子动力学的影响所产生的改变纹理的纳米通道，由改变分子/孔壁相互作用和由一个逐渐填充的纳米通道从膜凝聚态通过形成毛细管桥的通道的完全填充。后者将允许边界层的厚度的量化，边界层是在孔壁附近的层，其受到与孔壁的相互作用的强烈影响。为了优化杂化体系以用于真实的应用，所考虑的纯无序液晶将被掺杂以通过共自组装获得电荷转移复合物。对于散装系统，这种策略已被证明是非常成功的，以优化电传输性能。因此，我们打算探索这种方法也为受限的液晶态。我们的目标将通过结构敏感方法（X射线散射，光学双折射测量，差示扫描量热法等）的组合来实现。与分子迁移率相关的实验（介电谱、比热谱、准弹性中子散射）。为了将基础研究与应用联系起来，我们将尝试通过基于AFM的方法直接在（隔离）通道中测量离散液晶的局部电导率。该项目将极大地受益于两个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。为了保证这种密切的合作，联合项目会议和博士生的交流，以补充测量以及补充培训是植物（除了样品交换）。除了预期的协同效益的科学成果，这两个博士生将显着受益于他们的科学教育，从这个研究项目的合作精神。

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.