电荷性质对结晶性两性离子型嵌段共聚物自组装行为的影响及其机制

Crystallization-driven self-assembly (CDSA) has become a powerful strategy to control both the morphology and the size of block copolymer (BCP) assemblies. It is has been widely used to design and prepare ordered structures and functional nanomaterials. In a selective solvent, the core-crystalline BCPs may form amorphous micelles via hydrophobicity induced micellization and/or assemble into core-crystalline micelles via CDSA route. However, at present, the competition between these two routes in aqueous solution remains unclear. Although polyionic block may helpful for BCPs choosing CDSA route, relatively little is known about how the charges on the soluble block affecting the CDSA behavior of the BCPs in water. In this proposal, we start with the synthesis of a series of BCPs bearing a polycaprolactone (PCL) or polylactide (PLLA) core crystalline block and a zwitterionic corona block containing carboxybetaine groups. Then, these BCPs will be employed to study their self-assembly behaviors in selective solvents. The effects of solvent property, temperature, BCP structure, charges, and salt ions on the competition between the amorphous micellization route and the CDSA route will be deeply investigated. Then, we will focus on the kinetics of the controllable CDSA of the core-crystalline BCPs in water. The optimal conditions for the CDSA of BCPs in water will be summarized by changing the block ratio, charge, salt ions, and temperature. We anticipate to control the morphology and size of the micelles by manipulating the growth rate and growth sequence of the core-crystalline BCPs. Through this project, stable and uniform assemblies with controllable morphology and size can be obtained, which may have applications in drug delivery, optical materials, and catalysis.

嵌段共聚物结晶驱动自组装可精确调控组装体的形貌和尺寸，在材料设计与制备等方面具有重要科学价值。结晶性嵌段共聚物在选择性溶剂中可形成非晶和结晶胶束，取决于胶束化与结晶行为之间的竞争与协同关系。结晶嵌段上连接离子型非晶嵌段可增加亲水性，利于体系经历可控结晶过程形成组装体。然而，离子型共聚物胶束化与结晶过程的竞争机制及影响因素仍不清楚。电荷性质对结晶驱动自组装行为的影响规律和机制还不明确。本项目将构建系列含有聚己内酯/聚乳酸结晶链段和基于羧酸甜菜碱的两性离子型可溶链段的嵌段共聚物。系统研究溶剂、温度、嵌段比、电荷性质、盐离子等参数对胶束化和结晶驱动自组装这两种不同行为的影响规律和机制。重点考察结晶性离子型嵌段共聚物在水相中的可控结晶驱动自组装动力学过程，实现对晶体生长速率、生长顺序及形貌的控制，最后获得形貌及尺寸均一可控的组装体，为实现其在药物载体、光学材料、催化等方面的应用奠定材料基础。

本项目研究电荷性质及结晶行为对嵌段共聚物自组装行为的影响规律和机制。研究内容和取得的结果主要包括：（1）以聚苯乙烯-b-聚（4-乙烯基吡啶）（PS-b-P4VP）嵌段共聚物为模型，探究了电荷对其在挥发性乳液中的三维受限组装行为的影响。结果表明电荷性质显著影响共聚物的亲疏水性质、乳液液滴的渗透压，以及嵌段共聚物链段在油相中的构象。利用电荷性质的调控，实现了组装体形貌的调控；（2）以携带不同电荷的纳米粒子作为响应性助表面活性剂，研究了电荷性质对聚苯乙烯-b-聚二甲基硅氧烷（PS-b-PDMS）的三维受限组装行为的影响。通过对电荷性质的调控，改变乳液油-水界面性质，实现了嵌段共聚物微球形状和结构的可逆调控；（3）以半结晶性手性嵌段共聚物聚苯乙烯-b-聚右旋乳酸（PS-b-PDLA）为模型，探究其在乳液液滴中的结晶驱动组装及三维受限组装，揭示了溶剂性质、温度、聚合物结晶过程对组装结构的重要影响与作用机制，总结出在三维受限空间内形成手性结构的必备条件，并对其形成机理进行深入探讨，有助于人们对手性嵌段共聚物自组装的理解，特别是手性从微观层次的链段构象向介观层次的形貌与结构的传递过程。本项目研究结果揭示了电荷性质及电荷相互作用对非结晶性和半结晶性嵌段共聚物自组装行为的调控规律和机制。相关结果在Macromolecules、Aggregate、Langmuir等国内外期刊上发表论文8篇。