大环及其衍生聚合物的控制合成、结构转换与性能研究

Precise synthesis and topological transformation of cyclic polymers and their derivatives are of cardinal significance since they can play an important role in bridging property correlations among various topological polymers involving ring, star and graft polymers. By combination of molecular tailoring and topology reconstruction in macromolecular design, cyclic and linear segments act as basic building blocks to efficiently generate multicomponent, multi-stimuli-responsive and multi-conversional monocyclic polymers and their corresponding complex macromolecular architectures such as cyclic graft and dicyclic polymers, and the physical properties, structural conversions, and potential applications of the resultant polymers will be investigated. With the aid of reactive tailoring and couplable moieties based on stimuli-labile linkages, postpolymerization modification reactions involving concentration-dependent cyclization and step polymerization are performed to achieve reversible and irreversible topological transformations, and a wide range of topological polymers with same or different compositions will be obtained. On this basis, the dependence of integrated functions of polymer materials on chemical composition and types of stimuli responsiveness will be studied, the differences in physical properties of various polymers with distinct linking modes of chain segments will be elaborated, the connotation and major influencing factors of topology effect among monocyclic, dicyclic, multicyclic, graft, star and linear polymers with similar compositions will be revealed, and the great potential in smart materials will be explored. The implementation of this project can not only afford universal methods to synthesize cyclic polymers and their derivatives but also promote the sustainable development of synthesis, properties and applications of novel architectural polymers.

环状聚合物及其衍生物的精密合成与结构转换，为研究环状-星形-接枝等拓扑聚合物之间性能的内在关联搭建了一座重要桥梁，具有重要的科学意义。本项目将分子裁剪与拓扑重构融入大分子设计，以环状和线型链段为基本构筑单元，高效合成多组分、多响应和多转变型单环聚合物及其衍生的环状接枝和双环聚合物，并研究其物理性能、结构转变和潜在应用。以刺激断裂键为可裁剪和偶联位点，采用包括具浓度依赖性的闭环和逐步聚合在内的后修饰反应进行可逆和不可逆结构转变，获得多类组成相似或不同的拓扑聚合物。考察化学组成和刺激响应类型对材料功能集成的影响，阐述链段连接方式不同的聚合物之间物理性能的差异，揭示组成类似的单环-双环-多环-接枝-星形-线型聚合物中拓扑效应的内涵及主要影响因素，并探索它们在智能材料领域的潜在应用。本项目的实施将完善环状衍生聚合物的普适性合成方法，同时促进新型拓扑聚合物合成、性能及应用研究的可持续发展。

环状聚合物及其衍生物的精密合成与结构转换能为研究环状-星形-接枝等拓扑聚合物之间性能的内在关联搭建一座重要桥梁，相关研究具有重要科学意义。本项目将分子裁剪与拓扑重构融入大分子设计，以环状和线型链为基本构筑单元，高效合成多组分、多响应和多转变型单环聚合物及其衍生的环状接枝和双环聚合物，并研究其物理性能、结构转变和潜在应用。结合可控聚合和连接反应，本项目设计合成一系列组成丰富、具刺激响应性的单环、双环、多环、笼形、蝌蚪形、水母状、线接环和环状接枝等大环基拓扑聚合物。以反应性基团和刺激断裂键为可裁剪或偶联位点，采用闭环和偶联等后修饰反应进行可逆和不可逆结构转变，获得多类化学组成、分子量相似或不同的拓扑聚合物，如线型、星形、大环、线环缀合物和超支化聚合物。考察拓扑结构、分子参数、化学组成和外界刺激对材料性能的影响，深入揭示拓扑效应。在结构转变前后和过程中，聚合物的本体和溶液性能发生显著变化，有利于获得多重调控物理性能。合理引入温敏基元能赋予聚合物单一或双重LCST/UCST型相变行为，有效调控相变类型和相变温度。引入可结晶性和pH、温度、氧化等刺激响应性单元，有利于构建单一或组合因素调控的多级自组装体系（如刺激诱导自组装、结晶驱动自组装和水解诱导共组装），获得多种零维至三维纳米结构，并通过溶液pH和温度等因素诱导多重形貌转变。含特定基团的单环、多环和蝌蚪形聚苯乙烯能进行跨尺度自组装，它们在THF中能自组装成纳米管、球形胶束甚至发生宏观相分离。部分聚合物在智能材料和生物医用材料等领域具有一定应用前景。本项目发展和完善环状衍生聚合物的普适性合成方法，有效实现了多种拓扑聚合物和纳米结构的按需形成及相互转换，部分揭示线环结构设计和拓扑转变在材料性能及应用方面所带来的优势，能适当促进大环基聚合物相关研究的深入发展。