序列受控的手性聚酰亚胺的合成、自组装与多层次结构的研究

Sequence-controlled polymers are macromolecules in which different monomer units are arranged in an ordered fashion. The physical and chemical properties and structures of polymers can be comprehensively regulated with molecular sequence. However, the sequence resulted from direction of unsymmetric monomer units in main chain of polymers, such as head-to-head and head-to-tail structure, has absorbed very few attention among sequence-controlled polymers. This project studies chiral polyimides from biomass amino acids as chiral diamines. The unsymmetric nature of the chiral monomers will raise inherent sequence motif for chiral polyimides. Sequence-controlled synthesis, self-assembly, and topological structures of the chiral polyimides are the central contents of the research. This project will develop the chiral polyimides with sequence regulated with polymerization methods. The self-assembly and mechanism of the chiral polyimide will be investigated in scrutiny, of which the relevance of sequence is the most concerned aspect. How the chiral feature of monomer units is transcribed and inherited into the conformation of macromolecular chains and supramolecular architecture of the chiral polyimide will be paid more attention. The synergistic action of chiral structure and sequence structure to regulate supramolecular structure and nanoscale micromorphology is to be discovered in the project. By those research, the combination of chirality and sequence would bring about high diversity and complexity in structure of the polymer, which will lead to new type of polyimide with specific properties and designable function. The research will build fundamentals for the application of polyimides toward the new field of functional materials and smart materials.

序列受控的聚合物是指大分子链中不同单体以有序方式排列的聚合物，分子水平的序列受控可以在更高层次上调控聚合物的结构和物理化学性质。在序列受控的聚合物相关研究中，由非对称单体在聚合物主链中排列方向导致的头-头和头-尾序列结构所受关注甚少。本项目以氨基酸衍生物为手性二胺单体，利用手性单体的结构非对称特征，将序列结构引入到手性聚酰亚胺中，研究序列受控的手性聚酰亚胺制备、自组装及多层次结构。通过本项目的研究，建立序列结构可调控的聚合物合成方法，探索自组装过程和机制、及其与手性结构和序列结构的相关性，关注单体手性特征在聚合物多层次结构中的传递和继承，利用手性结构与序列结构协同调控聚合物超分子结构和纳米尺度结构的形成。上述研究将手性结构和序列结构相结合，将为聚酰亚胺带来新的结构多样性和复杂性，获得更加丰富和可设计的性质和功能，为其在新型功能材料和智能材料领域的应用奠定基础。

蛋白质中氨基酸序列决定了多肽链的精确自组装并形成特定的手性高次结构，是实现蛋白复杂生物功能的关键，单体序列和组成对有序高分子高次结构及性能同样具有重要的影响。目前为止，尚未有报道揭示出合成无序聚合物和单体单元序列受控聚合物的自组装行为的差异，分子链组成、单体单元排列方向与手性高分子的自组装及功能的关系研究将为新型功能聚合物的设计提供参考。本项目设计了具有不同组成和序列结构的手性聚酰亚胺，研究了其自组装与分子识别行为。首先设计合成了具有头头（HHPI）、头尾（HTPI）和无序（RPI）的序列结构的手性聚酰亚胺。具有三种序列结构的聚合物的自组装行为具有显著的序列依赖性，对布洛芬的对映体识别行为也具有显著差异，揭示了由序列差异导致的聚合物功能的多样化。该部分工作首次利用合成高分子揭示了序列结构对手性高分子自组装形成的高次结构和相关功能的影响。其次，设计合成了基于萘四酸双酰亚胺（NDI）的手性聚酰亚胺，该聚合物的自组装过程中发生了邻近生色团的手性堆积（M-螺旋），通过聚合物表现出不同的NDI˙ˉ吸收谱带和π-π*跃迁谱带，该聚合物可用于对多种弱碱性含氧阴离子（AcOˉ、PhCO2ˉ、ClO4ˉ和IO4ˉ）和卤素离子（Clˉ、Brˉ和Iˉ）的识别。进一步研究发现，该聚合物可被用于手性酸的对映体识别，不同对映体诱发的NDI˙ˉ吸收谱带和π-π*跃迁谱带具有显著差异。结合阴离子-NDI作用和聚合物的超分子自组装特性，我们首次实现了同一体系下对弱碱性阴离子和手性酸的广谱识别。本项目工作将有助于我们理解手性高分子微结构与自组装的关系，为通过控制单体序列实现人工合成高分子的多功能化提供借鉴。