RAFT polymerization: Adding to the picture
RAFT polymerization: Adding to the picture
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RAFT 聚合：添加到图片中
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
S. Thang
中科院分区：
文献类型：
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作者：
E. Rizzardo;M. Chen;Bill Chong;G. Moad;M. Skidmore;S. Thang
摘要：讨论了针对给定聚合影响 RAFT 试剂 [RSC(Z) = S] 选择的因素。对于甲基丙烯酸甲酯 (MMA) 的聚合，氰基烷基三硫代碳酸酯可以很好地控制分子量和分布，并且聚合反应几乎没有延迟。具有 R = CHPh(CN) 的仲三硫代碳酸酯 RAFT 试剂也能提供良好的控制，但由于缓慢重新引发而导致的抑制期很明显。使用次磷酸盐进行自由基诱导还原，为去除 RAFT 合成聚合物的硫代羰基硫端基提供了一种清洁且方便的方法。报道了两种同时控制自由基聚合形成的链的立体化学和分子量分布的方法。 MMA 在三氟甲磺酸钪存在下聚合可提供更全同立构的 PMMA。使用三硫代碳酸酯 RAFT 试剂的类似 RAFT 聚合也提供了控制并避免了在路易斯酸存在下使用二硫代苯甲酸酯 RAFT 试剂出现的 RAFT 试剂不稳定问题。甲基丙烯酸四甲基铵在 45°C 下进行 RAFT 聚合可提供分子量和分布受控的间同立构 PMMA（甲基化后；mm:mr:rr 2:21:77，而通过 MMA 本体聚合形成时为 3:35:62）。
SUMMARY: Factors affecting the choice of RAFT agent [RSC(Z) = S] for a given polymerization are discussed. For polymerization of methyl methacrylate (MMA), tertiary cyanoalkyl trithiocarbonates provide very good control over molecular weight and distribution and polymerizations show little retardation. The secondary trithiocarbonate RAFT agents with R = CHPh(CN) also gives good control but an inhibition period attributed to slow reinitiation is manifest. Radical induced reduction with hypophosphite salts provides a clean and convenient process for removal of thiocarbonylthio end groups of RAFT-synthesized polymers. Two methods providing simultaneous control over stereochemistry and molecular weight distribution of chains formed by radical polymerization are reported. Polymerization of MMA in the presence of scandium triflate provides a more isotactic PMMA. A similar RAFT polymerization with trithiocarbonate RAFT agents also provides control and avoids issues of RAFT agent instability seen with dithiobenzoate RAFT agents in the presence of Lewis acids. RAFT polymerization of tetramethylammonium methacrylate at 45 °C provides a more syndiotactic PMMA of controlled molecular weight and distribution (after methylation; mm:mr:rr 2:21:77 compared to 3:35:62 when formed by bulk polymerization of MMA).