PEG接枝大分子RAFT试剂的设计及其对无皂乳液RAFT聚合嵌段共聚物胶体结构的影响

The proposed project is focused on the macro-RAFT agent mediated with surfactant-free emulsion RAFT polymerization of styrene or acrylate and the structure evolution of the in situ synthesized block copolymer colloids. To get well-controlled surfactant-free emulsion RAFT polymerization and to achieve controlled evolution of the in situ synthesized block copolymer colloids, a special macro-RAFT agent of poly(ethylene glycol) grafted amphiphilic copolymer is employed. This macro-RAFT agent of the poly(ethylene glycol) grafted amphiphilic copolymer has three characters. First, it contains a terminal of the trithiocarbonate reactive group, which makes it suitable in the surfactant-free emulsion RAFT polymerization. Second, the macro-RAFT agent contains a hydrophobic polymer segment and a hydrophilic PEG-graft segment, and the hydrophilic/hydrophobic balance (HLB) of the macro-RAFT agent can be tuned. Third, the strong steric repulsion due to the densely grafted PEG brushes exists in the macro-RAFT agent. All the three characters make the macro-RAFT agent to be the suitable candidate for the surfactant-free emulsion RAFT polymerization of styrene or acrylate. Besides, the in situ synthesized colloids of block copolymer are expected to change their size and morphology with the increase in the monomer conversion, which is ascribed to both the adjustable HLB value and the strong steric repulsion of the macro-RAFT agent..The proposed project contains four items.First, synthesis of the macro-RAFT agent is introduced. Second, micellization of the macro-RAFT agent in water is explored. This macro-RAFT agent contains a hydrophobic segment and a hydrophilic segment and it is expected to form micelles in water. Due to the strong steric repulsion caused by the densely grafted PEG brushes, the micelles are expected to be interesting. Third, the polymerization kinetics, the increase of the molecular weight of the synthesized block copolymer with the monomer conversion, and the effect of the macro-RAFT agent on the surfactant-free emulsion RAFT polymerization are explored. Lastly, the structure evolution of the in situ synthesized block copolymer colloids with the increase in the molecular weight of the synthesized block copolymer is investigated, and the how the macro-RAFT agent effecting the evolution of the colloids are analyzed..The proposed project is anticipated to open a new way to synthesize the concentrated, stable, and morphology-tunable colloids of block copolymer in water.

本项目的研究目标，是通过大分子RAFT试剂（Macro-RAFT试剂）的设计，实现可控的无皂乳液RAFT聚合反应，制备浓度高、稳定性好、结构可调节的嵌段共聚物胶体。为此，合成亲/疏水性质和空间位阻可调节的聚乙二醇（PEG）接枝共聚物Macro-RAFT试剂，应用于苯乙烯或丙烯酸酯无皂乳液RAFT聚合。在无皂乳液RAFT聚合条件下，随着单体转化率增加，嵌段共聚物分子量Mn发生可控的增长，嵌段共聚物胶体的尺寸和形态发生规律性变化。PEG接枝Macro-RAFT试剂的结构，为实现可控的无皂乳液RAFT聚合和嵌段共聚物胶体结构的演变提供了可能。本项目旨在通过对Macro-RAFT试剂的结构对无皂乳液RAFT聚合的影响的研究，揭示嵌段共聚物的Mn和分子量分布系数PDI随单体转化的变化规律，揭示嵌段共聚物胶体的尺寸和形态的演变规律，探索出一条制备浓度高、稳定性好、结构可调节的嵌段共聚物胶体的有效方法。

两亲性嵌段共聚物胶体的制备和合成研究是高分子科学的一个重要方向。通过两亲性嵌段共聚物在选择性溶剂中的自组装是制备嵌段共聚物胶体的常用方法。这种自组装的方法有诸多优点，但是也存在难以克服的不足。在本项目研究中，用乳液RAFT聚合、分散RAFT聚合和种子RAFT聚合等非均相RAFT聚合方法进行了嵌段共聚物胶体的原位合成研究，揭示了在非均相RAFT聚合情况下嵌段共聚物胶体的形成机制，考察了macro-RAFT试剂的结构、macro-RAFT试剂的链长、macro-RAFT试剂的极性、聚合介质的组成和性质、疏溶剂嵌段的链长和极性等等诸多因素对RAFT聚合的动力学和嵌段共聚物胶体的结构的影响，对比考察了聚合方法（乳液RAFT聚合、分散RAFT聚合和种子RAFT聚合）对嵌段共聚物胶体结构的影响。合成了不同化学组成和不同形态结构的嵌段共聚物胶体。建立了通过非均相RAFT聚合原位合成浓度高、稳定性好、结构可调节的嵌段共聚物胶体的有效方法。