环形高分子关环合成新方法及其链序列结构的精密控制

The synthesis of cyclic polymers and sequence-controlled polymers has become a hot topic in recent developments of polymer chemistry. This proposal is focusing on developing novel ring-closure methods for the scalable preparation of cyclic polymers and their topological derivatives and controlling chain sequence of the resultant cyclic polymers based on light-induced click chemistry. The main research contents are detailed as following four aspects. (1) As a novel kind of bio-orthogonal reactions recently developed in organic chemistry, the UV-induced click chemistry will be combined with the controlled polymerization techniques to develop a series of novel, simple, clean, and efficient ring-closure methods for synthesizing varied cyclic polymers. Compared to the traditional ring-closure methods, the obvious advantages of these novel methods include: the ring-closure reactions only require mild UV light initiation, which could then be quickly finished in air and varied solvent systems; the ring-closure reactions have no metal catalyst requirements and only produce the gas by-products; the resultant pure cyclic polymer could be directly used after removing the solvent without any further purification. (2) By the combination of this powerful UV-induced ring-closure strategy with continuous-flow technique, a general and practical method of preparing varied cyclic polymers in large scale will be established. (3) Based on this simple, clean, and efficient techniques for synthesizing varied single cyclic polymers, further investigation to prepare the cyclic polymer derivatives with advanced topologies will be studied. (4) In addition, by taking advantage of the novel synthetic techniques for multi-block copolymers from controlled radical polymerization, and the alternating polymerization characteristic between styrene and maleimide-based monomers in controlled radical copolymerization, a novel strategy to accurately control the chain sequence of the resultant cyclic polymers will be given.

环形高分子的高效合成与高分子链结构精密控制已成为目前高分子化学领域的研究重点。本项目拟建立基于光诱导点击化学的环形拓扑结构高分子及其衍生物的批量合成新方法。具体研究内容包括：（1）结合光诱导点击化学与高分子可控聚合技术，开发各类环形高分子的简单、清洁、高效的关环合成新方法。其区别于传统方法的显著特点包括：关环反应仅需紫外光诱导、可在空气、各种溶剂体系中快速完成；关环反应无需金属催化剂且仅产生气态副产物；所得环形高分子简单脱除溶剂即可直接使用，无需进一步分离纯化。（2）进一步结合连续流技术，建立适用于不同聚合物种类的环形高分子大量合成通用方法。（3）在此基础之上，发展批量合成具有复杂拓扑结构的环形高分子衍生物的新方法。（4）结合目前可控自由基聚合高效合成多嵌段共聚物的技术，及苯乙烯和马来酰亚胺类单体可控自由基共聚优先交替聚合的特性，建立精确调控环形高分子链序列分布的新路径。

环形高分子因其无链末端的分子结构特征，具有一系列显著区别于传统线性高分子的物理化学特性。目前环形高分子的研究仍受限环形高分子的制备，因此发展高效、通用的环形高分子合成方法具有重要意义。本项目针对这一科学问题，运用点击化学（click chemistry）反应，以关环方法制备了一系列环形和线形高分子，并实现了链序列结构的精密构筑。.1. 以单电子转移活性自由基聚合技术（SET-LRP）构筑序列可控的线形高分子前体，以铜催化的叠氮-炔环加成（CuAAC）作为关环反应，以单分子关环实现了序列可控的环形高分子的构筑。.2. 发现了一类具有自加速效应的双重环张力促进的叠氮-炔环加成（DSPAAC）反应，能够在不等当量条件下，小分子连接子与大分子前驱体发生双分子关环制备环形高分子和复杂拓扑结构的环形高分子衍生物；通过在大分子前驱体中引入序列，可以实现对制备得到的高分子的链序列结构的精密调控。.本项目发展的一系列环形高分子合成方法具有反应前体易制备、反应条件温和、反应高效、官能团耐受性高等一系列特点，为环形高分子制备提供了一条高效、通用的路线。