基于“不对称时刻”设计与高效合成（多）嵌段型类梯度共聚物及其自组装的深入研究

Gradient copolymers have attracted more and more researchers’ attentions due to their unique composition profiles, intriguing properties, and potential applications. However, conventional synthetic approaches have many drawbacks, for instance, restricted monomer pairs, complex experimental setup, low reproducibility, and requiring careful control over monomer addition and constant feedback in order to regulate the composition at each stage of the polymerization. Therefore, researches regarding the properties and applications of gradient copolymers have been greatly limited. Based on this, this project aims to develop the concept of “Moment of Asymmetry”, which will be used to guide the calculation and design of the copolymers’ composition. One-pot reversible addition-fragmentation chain transfer (RAFT) polymerization will be utilized to prepare (multi)block gradient-like copolymers. This substantially easier and highly reproducible approach will offer new perspectives for the rapid and efficient synthesis of gradient copolymers and can be utilized to a wider range of monomers. The self-assembly behavior of the resulting copolymers in responding to the pH, temperature, and metal ions in aqueous solution will be investigated in order to explore the mechanisms of the self-assembly induced by the environmental stimuli and the methods of tuning the morphologies. It will enrich the knowledge regarding the self-assembly of copolymers. Researches above and the obtained results will provide theoretical and experimental foundation for the design and precise synthesis of unique and multi stimuli-responsive chemosensors, rapid detection materials, and drug delivery and controllable release materials.

梯度共聚物由于其独特的结构、性能和广阔的应用前景，吸引了越来越多科研人员的关注和研究。然而，常规的合成方法存在着单体选择受限、操作繁琐、需要花费大量时间持续跟踪以及可重复性低等缺陷，进而导致相应的性能和应用研究受到了极大的限制。基于此，本项目依据“Moment of Asymmetry” （不对称时刻），首先通过计算设计出共聚物的结构，进而通过简单易操作的“一锅煮”可逆加成-断裂链转移聚合，高效地制备（多）嵌段型类梯度共聚物，为梯度共聚物的合成提供一种便捷、单体适用性广且可重复性高的新方法；通过研究这一系列共聚物的自组装行为对诸如pH、温度和金属离子等刺激的响应性，明晰由外界环境引发的自组装行为的机理以及自组装形貌的调控策略，丰富和深化共聚物自组装领域的知识；为高分子的精密合成及功能调控和开发具有独特、多重响应性的化学传感器、快速灵敏检测材料和药物运输及可控释放材料提供理论和实验数据支持。

梯度共聚物由于其独特的结构和性能，在自组装、阻尼、形状记忆材料、生物医学等领域有着广阔的应用前景。然而，常规的合成方法具有单体选择受限、操作繁琐以及低重复性等缺点，导致其性能和应用研究受到极大的限制。基于此，本项目通过设计和调控共聚物的结构，运用可逆加成-断裂链转移（RAFT）聚合高效地合成具有梯度共聚物性质和功能的（多）嵌段共聚物。通过研究不同结构（多）嵌段共聚物在水溶液中的自组装行为对pH等外界刺激的响应性，分析外界刺激引发的自组装的机理和动态过程，总结形貌调控策略，为合成（类）梯度共聚物提供了一种新的合成方法，丰富了梯度共聚物的种类，并拓宽了其应用范围。.首先通过RAFT聚合将具有不同结构的单体对合成不对称二嵌段共聚物Poly(A84%-co-B16%)-b-Poly(A16%-co-B84%)和不对称三嵌段共聚物polyA21%-b-poly(A29%-co-B29%)-b-polyB21%，以及对照组嵌段共聚物PolyA50%-b-PolyB50%和线型梯度共聚物PolyA100%-grad-PolyB100%（其中A和B分别代表不同单体）。结果表明，不对称二嵌段共聚物具有与线型梯度共聚物相似的pH响应动态自组装行为，其水溶液中的自组装形貌可以随着pH值的变化实现从小粒径胶束到大粒径胶束，再到蠕虫状胶束，最后到囊泡的转变。进而将含有对极性敏感荧光基团的单体，通过RAFT聚合引入上述不对称二嵌段共聚物中，制备出具有pH响应的不对称二嵌段荧光共聚物。其不对称二嵌段结构增强了其刺激响应性，使其具有较宽的pH响应性，实现了动态荧光响应性，其荧光强度随着pH的降低而逐渐增大，且不依赖于浓度变化。研究结果为制备具有外界刺激响应性自组装体的构筑提供了一种便捷的合成方法，拓宽了共聚物在药物靶向递送和释放、生物探测以及荧光成像等领域的应用。