含多节弓形共轭链段的聚合物设计、制备及其用于半导体性碳纳米管的分离研究

Sorting single-walled carbon nanotubes (SWNTs) based on their different metallic and semiconducting natures as well as diameters is of vitally importance for their many applications. This project proposes to develop a kind of new polymeric SWNT-separating agents bearing multiple arch-shaped conjugated segments in their backbones. This kind of agents is different from traditional conjugated polymers and small molecules, and has its own structure features and advantages. Firstly, the binding between this kind of polymers and SWNTs would mainly occur through arch-shaped conjugated segments in the backbone, which have a definite structure and simple configuration, unlike conjugated polymers. Therefore, compared with conjugated polymers, it is easy for this kind of polymers to establish relationships between their structures and bound SWNTs. It would be useful to develop specific separating agents for desired SWNTs. Secondly, the binding between this kind of polymers and SWNTs is multidentate, different from monodentate that occurs in the case of conjugated small molecules. Such multidentate binding would produce chelating effect and enable a strong binding between this kind of polymers and SWNTs. Thirdly, the structure of this kind of polymers allows to introduce additional functions, such as photo-responsive, degradable, and recycling functions, by means of integrating photo-responsive moieties into arch-shaped conjugated segments, and/or reversible covalent bonds into non-conjugated segments. Therefore, the project will be endeavored to design and synthesize this kind of polymers, and investigate their properties in SWNT-sorting. Furthermore, the project will carry out the studies on charge transportation performance of the purified SWNTs and on their potential applications in transistors and sensors.

实现金属性与半导体性以及不同管径单壁碳纳米管之间的分离纯化，对于其诸多应用都十分重要。此项目提出开发一类具有多节弓形共轭链段的聚合物分离试剂，其结构不同于传统的共轭聚合物和小分子化合物，有着自己的特点和优势。首先，相对于构象复杂的共轭聚合物，此类聚合物与碳管之间的相互作用主要由结构明确构象简单的弓形共轭链段承担，因此较为容易建立其结构参数与结合碳管之间的关联关系，并由此指导特定结构碳管的分离试剂设计。其次，相对于小分子化合物，此类聚合物与碳管之间的作用是多点式，产生的螯合效应会大为提高聚合物与碳管的结合力。第三，此类聚合物容易在共轭链段植入光响应基团，也容易在非共轭链段引入可发生可逆反应的弱键，从而为体系叠加光响应、可降解和回收再利用的功能。项目将充分开展此类聚合物的设计、合成及用于单壁碳纳米管的分离研究，并进一步研究纯净单壁碳纳米管的载流子迁移特性及其在晶体管和传感器方面的应用。

根据电性的不同，单壁碳纳米管可分为金属性和半导体性两大类，各自具有不同的优异性能和使用领域。但目前各类制备方法所得的单壁碳管，混杂着这两类碳管，妨碍了其特长应用，需要分离纯化。在已开发的各类碳管分离纯化试剂中，利用芳环与碳璧的-相互作用选择性地增溶半导体性单壁碳管，从而将其与金属性碳管分离，是一种非破坏性的方法，受到越来越多的关注。本项目在课题组前期提出的“多节棍”聚合物半导体材料概念上，尝试开发适合单壁碳管分离纯化用的“多节棍”聚合物试剂。这是一类材料介于共轭聚合物和共轭小分子化合物之间的新型碳管分离纯化材料，其主链由结构明确的刚性共轭链段和柔性非共轭链段交替组成。项目总共设计合成了2大类8种“多节棍”聚合物，研究了其基本性质及其对单壁碳管的分离纯化性能，发现了以下的一些基本构效关系：（1）聚合物中柔性链长度对其包裹单壁碳管的能力有很大影响。合适的柔性链长度可以使聚合物拥有比全共轭聚合物更强的包裹能力，并且远高于商品化聚芴分离试剂PFO。（2）聚合物刚性链段的曲度对其包裹碳管的能力也有较大的影响，含1，3-苯撑为中心的刚性链段的聚合物，其包裹能力强于以1，4-苯撑相连的聚合物。（3）高分子量的聚合物表现出远高于低分子量聚合物的碳管包裹能力，体现了高分子量聚合物带来的更多相互作用点的益处。此外，项目还将“多节棍”聚合物拓展至有机场效应晶体管，发现小分子半导体化合物“多节棍”化能够显著提高成膜性和器件制备的均匀性和成功率。而且其优化后的迁移率也稍高于参比小分子化合物器件。这些结果表明，“多节棍”聚合物有其结构特点和性能特征，是一类较为优良的单壁碳管分离纯化试剂和有机场效应晶体管材料。