POLYMERIZATION OF METHYL-METHACRYLATE WITH THE CARBON-TETRACHLORIDE DICHLOROTRIS(TRIPHENYLPHOSPHINE)RUTHENIUM(II) METHYLALUMINUM BIS(2,6-DI-TERT-BUTYLPHENOXIDE) INITIATING SYSTEM - POSSIBILITY OF LIVING RADICAL POLYMERIZATION
POLYMERIZATION OF METHYL-METHACRYLATE WITH THE CARBON-TETRACHLORIDE DICHLOROTRIS(TRIPHENYLPHOSPHINE)RUTHENIUM(II) METHYLALUMINUM BIS(2,6-DI-TERT-BUTYLPHENOXIDE) INITIATING SYSTEM - POSSIBILITY OF LIVING RADICAL POLYMERIZATION
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DOI：
10.1021/ma00109a056
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发表时间：
1995-02-27
期刊：
影响因子：
5.5
通讯作者：
HIGASHIMURA, T
中科院分区：
文献类型：
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作者：
KATO, M;KAMIGAITO, M;HIGASHIMURA, T
导言。由于几乎没有链转移、终止和其他副反应，活性聚合是合成分子量和结构可控的聚合物的最佳方法之一。4因此，自从现在经典的阴离子体系被发现以来，5利用几乎所有的加成和开环聚合机制，已经发展了许多活性聚合反应，这并不奇怪。这方面仅存的前沿可能是活性自由基聚合，事实上，最近几个研究小组已经开始尝试这方面的工作。6-11然而，在我们看来，定义明确、用途广泛的活性自由基聚合仍然遥不可及，而且还没有建立起实现活性或受控自由基聚合的一般原则。造成这一困难的主要原因包括自由基的高活性或低稳定性及其容易偶联和/或歧化反应。最近，我们已经实现了乙烯基化合物的活性阳离子聚合物，由于高活性的碳阳离子生长物种的不稳定性和它们容易发生链转移反应，聚合反应的控制一直被认为是非常困难的。12-13在这些活的阳离子过程中，不稳定增长的碳正离子被认为是通过相应的共价或休眠物种的可逆形成而被“稳定”的，这些共价或休眠物种迅速与离子对应物交换。14例如，乙烯基醚与HCl/ZnCla引发体系的活性阳离子聚合涉及中间体(1)与来自氯化氢(引发剂)和单体的碳-氯端键，1中的共价端被ZnCl2可逆地活化为碳阳离子形式(2)，该形式实际上与单体(方程1)一起传播。我们最新的核磁共振分析
Introduction. Because of the virtual absence of chain transfer, termination, and other side reactions, living polymerization is among the best methods for the synthesis of polymers with controlled molecularweights and architectures. 4 It is therefore not surprising that, since the discovery of the now classical anionic systems, 5 a number of living polymerizations have been developed by utilizing almost all of the mechanisms of addition and ring-opening polymerizations. 4 Perhaps the only remaining frontier in this aspect would be living radical polymerization, for which attempts have in fact been started quite recently in several research groups. 6-11 In our view, however, well-defined, highly versatile living radical polymerizations are still beyond our reach, and no general principles have been established to achieve living or controlled radical polymerizations. The pri-mary reasons for the difficulty include the high reactiv-ity or low stability of free radicals and their facile coupling and/or disproportionation reactions. Recently, we have achieved living cationic polymer-ization of vinyl compounds, where control of the polym-erization has long been considered very difficult, due to the instability ofthe highly reactive carbocationic growing species and their tendency to undergo chain-transfer reactions. 12-13 In these living cationic processes, the unstable growing carbocations are considered to be “stabilized” via the reversible formation of the cor-responding covalent or dormant species that rapidly exchange with the ioniccounterparts. 14 For example, the living cationic polymerizations of vinyl ethers with the HCl/ZnCla initiating system involve theintermedi-ate (1) with a carbon-chlorine terminal bond derived from hydrogen chloride (initiator) and the monomer, and the covalent end in 1 is reversibly activated by ZnCl2 into the carbocationic form (2) that actually propagates with monomer(eq 1). Our recent NMR analysis of