Towards New Synthetic Methodologies for the Preparation of Well-Defined Carbon Nanomaterials

碳纳米材料，如富勒烯、碳纳米管和石墨烯，具有优异的电子和光学性能。然而，许多潜在的应用需要具有明确结构和性能的碳纳米材料，这些材料仍然无法通过基于碱性碳原料的高温转化的传统合成方法获得。在上一个资助期内，我们承担了一个创新的研究项目，在温和的条件下制备碳纳米材料，从而更好地控制它们的大小、形状、功能和化学性质。这种新方法被称为“混合方法”，它允许我们从反应性的、自组装的含低聚烷的构建块（如线性低聚物、大环和星形分子）中制备碳纳米材料。在本提案中，我们打算利用我们最近开发的工具进一步推动混合策略，以开发碳纳米材料，更准确地说，石墨烯纳米带和富碳纳米管，其结构特性（尺寸，形状，宽度，长度，长宽比等）和化学性质可以精确调制。我们的策略将提供具有定制光学和电子特性的新型碳纳米材料，这些特性是用已知的合成方法无法获得的。我们制备不同宽度的石墨烯纳米带的策略依赖于制备芳基附加聚二乙炔（pda）作为反应前体，在温和的条件下使用物理刺激（光，温热）进行多次环芳化反应，以获得所需的材料。具有精心选择的官能团的初始pda将使用自组装寡聚物的拓扑化学聚合或涉及C-C偶联反应的更传统的溶液化学来制备。利用这些方法，还可以制备不同宽度的不对称石墨烯纳米带。富碳纳米管将采用自组装的含丁二炔大环的拓扑化学聚合制备。本文将利用近年来发展的共轭二炔复分解反应制备具有不同尺寸和化学功能的大环，该反应将适用于共轭大环的制备。所有新的碳纳米材料将使用光学和振动光谱、热分析、电子显微镜、电化学和x射线衍射进行严格的表征，以研究其光学、电子和形态特性。最好的材料将作为太阳能电池和场效应晶体管的半导体材料进行测试。我们提出的石墨烯纳米带和纳米管的合成策略将导致迄今为止任何其他合成方法都无法获得的碳纳米材料。此外，通过细微的化学修饰，石墨烯纳米带和富碳纳米管的结构参数“按需”变化可能会产生巨大的影响，特别是在需要“接近完美”材料的电子工业中。尽管如此，在这些方法被学术界和工业界的材料科学家定期使用之前，还需要做大量的基础研究工作。这项资助将是我们在碳纳米材料领域做出重大贡献的绝佳机会。由于其多学科性质，这些项目也将大力促进HQP的培训，他们的技能将在以后使私营和公共研究实验室受益。

Carbon nanomaterials such as fullerenes, carbon nanotubes, and graphene, have outstanding electronic and optical properties. However, many potential applications require carbon nanomaterials with well-defined structures and properties that still cannot be reached through conventional synthetic methods, which are based on high-temperature transformations of basic carbon feedstock. During the last funding period, we undertook an innovative research program for the preparation of carbon nanomaterials using mild conditions, allowing better control over their sizes, shapes, functions, and chemical natures. The new approach, called the “hybrid method,” allowed us to prepare carbon nanomaterials from reactive, self-assembled oligoyne-containing building blocks such as linear oligomers, macrocycles, and star-shaped molecules. In this proposal, we intend to use the tools we have recently developed to push the hybrid strategy further with the aim to develop carbon nanomaterials, more precisely graphene nanoribbons and carbon-rich nanotubes, whose structural properties (size, shape, width, length, aspect ratio, etc.) and chemical nature can be precisely modulated. Our strategies will provide novel carbon nanomaterials with customized optical and electronic properties that cannot be acquired using known synthetic methods. Our strategy to prepare graphene nanoribbons with different widths relies on the preparation of aryl-appended polydiacetylenes (PDAs) as reactive precursors that will undergo multiple cycloaromatization reactions using physical stimuli (light, gentle heat) under mild conditions to give the desired materials. The initial PDAs with carefully chosen functional groups will be prepared using either the topochemical polymerization of self-assembled oligoynes, or more traditional solution chemistry involving C-C coupling reactions. Using these methods, asymmetric graphene nanoribbons with different width will also be prepared. The carbon-rich nanotubes will be prepared using the topochemical polymerization of self-assembled butadiyne-containing macrocycles. Macrocycles with different sizes and chemical functions will be prepared using the recently developed conjugated diynes metathesis reaction that will be adapted for the preparation of conjugated macrocycles. All the new carbon nanomaterials will be rigorously characterized using optical and vibrational spectroscopy, thermal analysis, electronic microscopy, electrochemistry and X-ray diffraction to study their optical, electronic and morphological properties. The best materials will be tested as semiconducting materials in solar cells and field-effect transistors. The synthetic strategies we propose for both graphene nanoribbons and nanotubes will lead to carbon nanomaterials that cannot be accessed by any other synthetic methods reported so far. Moreover, “on-demand” variations of structural parameters in both graphene nanoribbons and carbon-rich nanotubes through subtle chemical modifications could have a tremendous impact, especially in the electronics industry where "close-to-perfect" materials are required. Nonetheless, a lot of fundamental research work needs to be done before these methods can be used on a regular basis by materials scientists in academia and industry. This grant will be an excellent opportunity for us to make significant contributions in the area of carbon nanomaterials. Because of their multidisciplinary nature, these projects will also strongly contribute to the training of HQP whose skills will benefit private and public research laboratories later on.