Ab initio Emulsion Polymerization by RAFT (Reversible Addition-Fragmentation Chain Transfer) through the Addition of Cyclodextrins
Ab initio Emulsion Polymerization by RAFT (Reversible Addition-Fragmentation Chain Transfer) through the Addition of Cyclodextrins
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通过添加环糊精进行 RAFT（可逆加成-断裂链转移）从头开始乳液聚合
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发表时间：
2006
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通讯作者：
M. Morbidelli
中科院分区：
文献类型：
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作者：
B. Apostolovic;F. Quattrini;A. Butté;G. Storti;M. Morbidelli
提出了一种在乳液中RAFT聚合制备均聚物和共聚物的新工艺。众所周知，RAFT控制的自由基聚合可以在乳液聚合中进行，而不会干扰该过程的自由基分离特性，从而导致聚合速率与相应的非活性体系中的聚合速率相同。然而，RAFT试剂的特点通常是水溶性很低，因此，它们从最初溶解的单体液滴扩散到反应地点，即聚合物颗粒，扩散速度非常慢。因此，当用于乳液聚合时，它们实际上被排除在反应之外。在这项工作中，我们证明了环糊精，众所周知，它们能够与疏水分子形成水溶性络合物，促进RAFT试剂的H2O相向聚合物颗粒的传输。因此，链在整个过程中以受控的方式增长。这导致了具有明确结构和末端官能度的低多分散性聚合物的生产，以及通过自由基机理合成嵌段共聚物的可能性。
A novel process to produce homo- and copolymers by RAFT polymerization in emulsion is presented. It is known that RAFT-controlled radical polymerization can be conducted in emulsion polymerization without disturbing the radical segregation characteristic of this process, thus leading to polymerization rates identical to those encountered in the corresponding nonliving systems. However, RAFT agents are often characterized by very low water solubility and, therefore, they diffuse very slowly from the monomer droplets, where they are initially solubilized, to the reaction loci, i.e., the polymer particles. Accordingly, when used in emulsion polymerization, they are practically excluded from the reaction. In this work, we show that cyclodextrins, well-known for their ability to form water-soluble complexes with hydrophobic molecules, facilitate the transport across the H2O phase of the RAFT agent to the polymer particles. Accordingly, chains grow through the entire process in a controlled way. This leads to the production of low-polydispersity polymers with well-defined structure and end functionalities as well as to the possibility of synthesizing block copolymers by a radical mechanism.