液晶相下螺旋聚二乙炔材料的可控合成与应用

Chirality plays an important role in chemistry, materials, and biology systems. In particular, the introduction of chiral nanostructure into conjugated polymer materials is expected to induce novel optical, electrical and magnetic properties, and tremendous potential applications, such as chiral separation, display materials, asymmetric electrode, enantio-selective sensing and biological medicine. In the past few decades, helical conjugated polymers have been prepared by various methods including the polymerization of optically active monomers, supramolecular assembly, enzyme catalyzed, template synthesis, and electrochemical polymerization. To date, the synthesis of helical conjugated polymer from achiral monomer in the absence of any chiral dopant or catalysts still remains a challenge. Recently, we reported the successful synthesis of chiral polydiacetylene (PDA) films by means of circular polarized light (CPL) irradiation. However, the asymmetric polymerization mechanism with CPL is still not clear and sometimes the helical direction of PDA chains could not be controlled when the interaction between the head groups of diacetylene (DA) monomers is too strong. One possible solution is the photo- polymerization of mesogenic DA monomers in the liquid crystal phase by means of CPL irradiation. The disc-shaped mesogenic DA monomers are of particular interest as they can stack in columns, and zipping of DA along the column axis by polymerization will lead to special optical and electrical properties. Whether the formation of helical PDA chains could be controlled in the liquid crystal reaction field by CPL irradiation still remains a question to be answered. Moreover, compared with the well-established technique using CPL, the asymmetric polymerization based on the magnetochiral dichroism mechanism has seldom been described to date. In this application, we will develop a novel facial and effective approach to synthesize helical PDA chains in the liquid crystal reaction field by CPL irradiation or based on magnetochiral dichroism mechanism. We will study the effect of the structure of the mesogenic units, the assembly condition, and the packing structure of the mesogenic DA monomer on the formation of helical PDA chains, and explore the rule of the construction and modulation of the helical structure for PDA materials. Further, electrical- responsive functional groups (including viologen, ferrocene units) will be introduced into helical PDA system and the helical structure of PDA chain would be modulated by external electrical stimuli. Finally, we will prepare helical PDA assemblies with special recognition units, and study their enantio-selective recognition properties for amino acids and saccharide derivatives. Above studies may render the helical PDA materials potential candidates for the application in smart materials and enantio-selective sensing area.

螺旋共轭聚合物具有独特的光学和电磁学特性，在手性分离、不对称电极及生物医药等领域拥有广阔的应用前景。目前有必要发展从非手性单体出发，不加入手性添加剂的情况下高效选择性合成螺旋共轭聚合物材料的新方法。本申请拟将液晶相模板控制合成技术与圆偏振光辐照及磁光二向色性效应相结合，制备具有独特取向结构和光电特性的螺旋聚二乙炔功能材料：重点关注介晶基元结构、液晶微区大小、取向等对聚二乙炔螺旋结构形成及材料宏观光电特性的影响，揭示螺旋聚二乙炔材料合成过程中可能的不对称诱导作用机制；将二茂铁、紫精等电响应基元引入到螺旋聚二乙炔体系，制备电致螺旋结构可调的新型聚二乙炔功能材料，研究螺旋结构调控过程中聚二乙炔材料光电特性变化，认识材料结构与性能的关系；在此基础上，构筑含硼酸基等识别基团的新型螺旋聚二乙炔功能材料，揭示其选择性识别机理，为其在智能材料及对映体选择传感等领域的应用提供理论基础和关键技术。

手性是自然界的基本属性之一，在生命体中手性大分子特有的不对称结构在维持生命过程、新陈代谢和进化等方面均起着决定性的作用。受此启发，构筑具有螺旋结构的共轭聚合物，研究其独特的物理化学性质和功能，探究其在对映体识别和拆分、不对称催化、信息存储与通讯等领域的应用已成为目前研究的热点。在国家自然科学基金（21574120）的资助下，我们通过点击化学、酰胺化反应以及超分子组装等方法构筑了一系列以三唑衍生物、苯并菲及卟啉衍生物为核，长链二乙炔为臂的新型盘状二乙炔单体，研究了介晶基团结构、组成、烷基链长等对液晶相结构以及聚合行为的影响；深入探讨了圆偏振光作为手性源，在盘状二乙炔单体超分子组装及不对称光聚合过程中的手性引入、传递、放大及调控机制。研究发现对于以三唑衍生物为核的盘状二乙炔单体，其在晶相和液晶相下均能发生光聚合，且液晶相下聚合速率更快；圆偏振光辐照在液晶相下能诱导盘状二乙炔单体聚合制备螺旋聚二乙炔功能材料，而在晶相聚合不能制备螺旋聚二乙炔功能材料。我们比较了连接基团结构、桥连化学键类型、单体堆砌结构等对体系手性引入、传递和放大效率的影响。对于以三唑衍生物为核的盘状二乙炔单体，在液晶相下引入强磁场以及与磁场方向平行或反平行的线偏振紫外光辐照聚合，能成功实现螺旋聚二乙炔功能材料的可控合成。在聚二乙炔微米管表面修饰电响应的紫精基团，通过施加电压控制紫精基团结构及其与红相聚二乙炔材料间的荧光共振能量转移，实现了聚二乙炔材料荧光性能的电致可逆调控，构筑了新型聚二乙炔智能光子学器件。在此基础上，我们利用超手性光场构筑了高光学活性的螺旋聚二乙炔组装体，系统研究了螺旋聚二乙炔组装体光学活性对其选择性识别能力的影响；通过圆偏振光诱导盘状二乙炔单体组装我们制备了螺旋聚二乙炔纳米组装体，揭示了螺旋结构与材料光电性能间的关系，为其在对映体选择传感、手性微纳光电器件等领域的应用提供关键技术和理论基础。