摘要/Abstract

超分子聚合物被认为是一种新型的动态材料，对超分子聚合过程的研究不仅有助于理解自组装规律，而且为开发智能材料提供理论支持.研究了对亚苯基桥联的双脲基嘧啶酮（UPy）衍生物M1~M3的四重氢键超分子聚合.这些单体分子之间的唯一区别是其间隔基（寡聚乙二醇）的长度不同.通过测试随单体浓度变化的¹H NMR，NOESY和粘度等研究了这些单体分子基于环链平衡的超分子聚合行为.结果表明间隔基长度对开环超分子聚合过程有显著影响.其原因是环状单体中亚苯基与二聚UPy之间的π-π相互作用强度不同.具有最短间隔基的M1缺乏π-π作用，而具有最长间隔基的M3具有较弱的π-π作用，因此二者的临界聚合浓度都较低；相比之下，间隔基长度适中的M2具有较强的π-π作用，从而导致其有较高的临界聚合浓度（189 mmol·L^-1）.最后，进一步研究了M1~M3与缺电子环番“blue-box”之间的相互作用，显示只有M3与环番发生主客体作用.该模型促进了对分子结构与超分子聚合之间紧密关系的认识，这对精确调控超分子聚合以及开发定制材料都具有重要意义.
关键词: 超分子化学, 四重氢键, 自组装, 超分子聚合物, 大环, 主客体作用
Supramolecular polymers are regarded as a new kind of dynamic materials. The study of supramolecular polymers not only helps to understand the law of self-assembly, but also provides theoretical support for the development of smart materials. Herein, three dioxyphenylene bridged ditopic ureidopyrimidinone (UPy) derivatives M1~M3 are studied. These molecules could undergo supramolecular polymerization via quadruple hydrogen bonding. The only difference in their structure is the length of the oligo(ethylene oxide) chain as spacers. The supramolecular polymerization based on ring-chain equilibrium of these molecules were studied by a series of experiments including concentration-dependent ¹H NMR, NOESY, and viscosity measurement, which showed that the spacer length has a big impact on the ring-opening supramolecular polymerization process. And the main reason for this is the different strengths of π-π interaction between the dioxyphenylene unit and the dimerized UPy motif in the cyclic monomer form. M1 with the shortest spacer lacks this kind of π-π interaction while M3 with the longest spacer possesses a weak π-π interaction, both leading to small value of CPCs. By contrast, M2 with a moderate length of spacer has a strong π-π interaction, resulting in a high CPC value (189 mmol·L^-1). Finally, the host-guest complexation between M1~M3 with the π-electron deficient bipyridinium-based cyclophane “blue-box” were further investigated, which shows that only M3 could perform host-guest complexation. From this interesting model, new insight into the relationship between molecular structure and supramolecular polymerization is discovered, which is important for creating tailor-made supramolecular polymeric materials.
Key words: supramolecular chemistry, quadruple hydrogen bonds, self-assembly, supramolecular polymer, macrocycles, host-guest interaction


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