Materials Chemistry of Self-Assembling Dyes

有机染料在我们的环境中无处不在，对特定技术性能改进的新染料的需求不断增加。Eichhorn团队开发了一种类似于传统液晶的特殊分子排列染料。这种在分子长度尺度（纳米结构）上对材料结构的控制对于染料薄膜和颗粒的性质的调整与染料本身的分子结构的调整同样重要。本文提出了有机染料的新设计标准：(1)自组装成具有芳香基团之间强相互作用的各向异性材料；(2)形成具有明确纳米结构的单分子厚膜。具有这些结构的材料有望产生前所未有的性能，有利于它们在广泛的不同技术中的应用，这些技术具有重要的商业意义，如有机半导体、高压润滑剂、光学薄膜和传感器。***主题1挑战范式柔性侧链是设计有机分子和由较大共轭/芳香族结构组成的聚合物所必需的，因为这些刚性芳香族结构不溶且难以加工。明智地选择侧链及其附着点的类型也被证明可以增强对这些分子在材料中的排列和排列的控制。然而，柔性侧链的使用有重要的缺点，因为它经常降低分子的热稳定性，排除某些纯化和处理方法（例如升华），不利于某些包装安排，并阻碍有机半导体应用中的电荷传输。本文提出的主要目的是为无侧链多环芳香族染料制定合理的分子设计标准，使其可以加工成类似的分子排列，并确定优于含侧链类似物的材料性能。***主题2的研究是基于该小组最近在控制界面上薄膜中染料分子的排列方面取得的成功。多环芳香族染料通常在界面上形成分子堆积的聚集体，并以边朝上的方向自组装。这种分子排列改变了它们的光吸收，常常抑制它们的荧光。它还在表面上产生相当致密的层，阻止染料分子与环境中的分子相互作用，例如分析物和衬底表面。Eichhorn的团队已经开发出了两亲性染料，这种染料在界面上是平的，这里提出的研究的主要目标是优化这些类型的染料分子的分子设计标准，通过交联它们的薄膜来增强稳定性，并展示它们在传感、表面涂层和纳米颗粒的功能钝化方面的应用优势。

Organic dyes are ubiquitous in our environment and new dyes with improved properties for specific technologies are constantly in demand. The Eichhorn group develops dyes that assemble into specific molecular arrangements similar to conventional liquid crystals. This type of control over the structure of materials at molecular length scales (nanostructure) is as important for the adjustment of properties of dye films and particles as the molecular structure of the dye itself. In this proposal new design criteria are proposed for organic dyes that (1) self-assemble into anisotropic materials with strong interactions between aromatic groups and (2) form one molecule thick films of defined nanostructures. Materials with these structures are expected to generate unprecedented properties that benefit their application in a wide range of different technologies that are commercially important, such as organic semiconductors, high pressure lubricants, optical films, and sensors.***Topic 1 challenges the paradigm flexible side-chains are required for the design of organic molecules and polymers consisting of larger conjugated/aromatic structures because these rigid aromatic structures are otherwise insoluble and difficult to process. Judicious choice of the types of side-chains and their attachment points has also been shown to enhance control over the arrangement and alignment of these molecules in a material. However, the utilization of flexible side-chains has important disadvantages as it often lowers thermal stability of the molecules, excludes certain purification and processing methods (e.g. sublimation), disfavors certain packing arrangements, and hinders charge transport in applications as organic semiconductors. The main objective of the work proposed here is to develop rational molecular design criteria for side-chain free polycyclic aromatic dyes that can be processed into similar molecular arrangements and identify materials properties that are superior to those of side-chain containing analogues.***Research proposed for topic 2 builds on the group's recent success in controlling the alignment of dye molecules in thin films at interfaces. Polycyclic aromatic dyes commonly form aggregates of stacking molecules and self-assemble with an edge-on orientation at interfaces. This molecular arrangement alters their light absorption and often suppresses their fluorescence. It also generates a rather dense layer on a surface that hinders the dye molecules from interacting with molecules in the environment, such as analytes, and the substrate surface. Eichhorn's group has developed amphiphilic dyes that orient flat-on with regard to an interface and the main objective of the research proposed here is to optimize the molecular design criteria for these types of dye molecules, to cross-link their thin films for enhanced stability, and to demonstrate their advantages for applications in sensing, surface coatings, and functional passivation of nanoparticles.