Instant living cationic polymerization using SnCl4/EtAlCl2 with a weak lewis base : Ultrafast polymerization in seconds
Instant living cationic polymerization using SnCl4/EtAlCl2 with a weak lewis base : Ultrafast polymerization in seconds
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DOI：
10.1002/pola.20902
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发表时间：
2005-09
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影响因子：
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通讯作者：
Tomohide Yoshida;Arihiro Kanazawa;S. Kanaoka;S. Aoshima
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文献类型：
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作者：
Tomohide Yoshida;Arihiro Kanazawa;S. Kanaoka;S. Aoshima
各种单体的活性聚合是近年来精密合成大分子的一个重要方面。在活性聚合过程中，必须稳定生长的活性物质，这通常会导致聚合速度低于常规（非活性）聚合的速度。例如，在活性阳离子聚合中，确保活性离子和休眠离子之间的平衡以抑制不希望发生的副反应，会显著降低活性离子的浓度，从而导致相对缓慢的聚合。类似的稳定生长物种的方法已经应用于活性自由基聚合，这也是一个缓慢的反应。从工业角度来看，加快反应速度对活性聚合的实际应用至关重要。7,8例如，各种应用都需要即时聚合，包括聚合物涂层，光刻胶和生物医学聚合物，如牙齿填充物。最近，我们报道了用SnCl4和EtAlCl2在酯作为添加碱的存在下进行乙烯基醚的快速阳离子聚合。反应在几分钟内完成，反应对象不仅包括烷基乙烯醚，还包括带有杂原子的乙烯醚。研究还发现，碱的碱性决定了碱稳定生物体系的反应速率，碱越弱，聚合越快。受这些最新发现的启发，我们研究了在弱碱氯乙酸乙酯存在下，使用SnCl4/EtAlCl2体系进行乙烯基醚的即时活性阳离子聚合。该体系的典型反应在1-2秒内完成，并得到分子量和分布高度可控的聚合物。这表明，在普通催化剂和反应装置的条件下，可以实现瞬间活性聚合。
The living polymerization of various monomers is an important aspect of recent progress in the precision synthesis of macromolecules. 1–5 In the living polymerization process, the growing active species must be stabilized, and this often causes the rate of polymerization to drop below that of conventional (nonliving) polymerization. In living cationic polymerization, for example, ensuring equilibrium between the active and dormant species to suppress undesired side reactions reduces the concentration of active ionic species significantly, resulting in relatively slow polymerization. 6 Similar methods for the stabilization of growing species have been applied in living radical polymerization, which is also a slow reaction. 5 Speeding up the reaction is crucial for the practical use of living polymerization from an industrial viewpoint. 7, 8 For example, instant polymerization is required for various applications, including polymer coatings, photoresists, and biomedical polymers such as teeth fillings. Recently, we reported the fast living cationic polymerization of vinyl ethers using SnCl4 combined with EtAlCl2 in the presence of an ester as an added base. 9 The reactions were completed within several minutes with not only alkyl vinyl ethers but also vinyl ethers with heteroatoms in the pendant. It was also found that the basicity of the added base determines the reaction rate for the base-stabilizing living system, 10, 11 with weaker bases resulting in faster polymerization. 12Motivated by these recent findings, we investigated the instant living cationic polymerization of vinyl ethers using this SnCl4/EtAlCl2 system in the presence of a weaker base, ethyl chloroacetate. Typical reactions with this system were found to complete within 1–2 s and give a polymer with a highly controlled molecular weight and distribution. This demonstrates that instant living polymerization can be achieved with ordinary catalysts and reaction apparatus.