Living free-radical polymerization by reversible addition-fragmentation chain transfer: The RAFT process
Living free-radical polymerization by reversible addition-fragmentation chain transfer: The RAFT process
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DOI：
10.1021/ma9804951
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发表时间：
1998-08-11
期刊：
影响因子：
5.5
通讯作者：
Thang, SH
中科院分区：
文献类型：
--
作者：
Chiefari, J;Chong, YK;Thang, SH
我们希望报道一种具有卓越有效性和多功能性的新型活性自由基聚合。 1 活性特征是由一类容易获得的有机试剂 (1) 赋予的，并且操作简单。该机制涉及可逆加成-断裂链转移，我们将该过程指定为RAFT聚合。 RAFT 聚合与所有其他受控/活性自由基聚合方法的区别在于，它可以与多种单体和反应条件一起使用，并且在每种情况下，它都能提供具有非常窄的多分散性（通常< 1.2；有时< 1.1）的受控分子量聚合物。活性聚合工艺具有许多优点。这些包括控制分子量和多分散性以及制备使用其他方法不易合成的复杂结构材料的嵌段共聚物和其他聚合物的能力。因此，人们可以理解当前开发一种真正有效的工艺的动力，该工艺将活性聚合的优点与自由基聚合的多功能性和便利性结合起来。 2-4 然而，“活性自由基聚合”下描述的现有工艺存在许多缺点。特别地，它们可能仅适用于有限范围的单体，需要昂贵或难以去除的试剂，需要特殊的聚合条件（例如高反应温度），和/或表现出对酸或质子单体的敏感性。这些因素为寻找新的更好的方法提供了动力。已经提出了三种主要机制来实现活性自由基聚合。 2, 5 第一种是通过偶联可逆终止的聚合。目前，此类中最好的例子是烷氧基胺引发的或硝基氧介导的聚合，如 Rizzardo 等人首先描述的。 6、7 以及最近被许多小组用于合成窄多分散性聚苯乙烯和相关材料。 4, 8第二种机制是自由基聚合，通过配体转移到金属络合物（通常缩写为 ATRP）来可逆终止。 9, 10 该方法已成功应用于各种丙烯酸和苯乙烯单体的聚合。实现活性特性的第三种机制是具有可逆链转移的自由基聚合（也称为退化链转移2）。此过程的简化机制如图所示
We wish to report a new living free-radical polymerization of exceptional effectiveness and versatility. 1 The living character is conferred by a readily available class of organic reagents (1) and is simple to perform. The mechanism involves Reversible Addition-Fragmentation chain Transfer, and we have designated the process the RAFT polymerization. What distinguishes RAFT polymerization from all other methods of controlled/living free-radical polymerization is that it can be used with a wide range of monomers and reaction conditions and in each case it provides controlled molecular weight polymers with very narrow polydispersities (usually< 1.2; sometimes< 1.1). Living polymerization processes offer many benefits. These include the ability to control molecular weight and polydispersity and to prepare block copolymers and other polymers of complex architecturesmaterials which are not readily synthesized using other methodologies. Therefore, one can understand the current drive to develop a truly effective process which would combine the virtues of living polymerization with versatility and convenience of free-radical polymerization. 2-4 However, existing processes described under the banner “living free-radical polymerization” suffer from a number of disadvantages. In particular, they may be applicable to only a limited range of monomers, require reagents that are expensive or difficult to remove, require special polymerization conditions (eg high reaction temperatures), and/or show sensitivity to acid or protic monomers. These factors have provided the impetus to search for new and better methods. There are three principal mechanisms that have been put forward to achieve living free-radical polymerization. 2, 5 The first is polymerization with reversible termination by coupling. Currently, the best example in this class is alkoxyamine-initiated or nitroxidemediated polymerization as first described by Rizzardo et al. 6, 7 and recently exploited by a number of groups in syntheses of narrow polydispersity polystyrene and related materials. 4, 8The second mechanism is radical polymerization with reversible termination by ligand transfer to a metal complex (usually abbreviated as ATRP). 9, 10 This method has been successfully applied to the polymerization of various acrylic and styrenic monomers. The third mechanism for achieving living character is free-radical polymerization with reversible chain transfer (also termed degenerative chain transfer2). A simplified mechanism for this process is shown in