Aqueous metal-catalyzed living radical polymerization: highly active water-assisted catalysis
Aqueous metal-catalyzed living radical polymerization: highly active water-assisted catalysis
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DOI：
10.1038/pj.2011.59
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发表时间：
2012-01
期刊：
影响因子：
2.8
通讯作者：
M. Ouchi;Hiroaki Yoda;Takaya Terashima;M. Sawamoto
中科院分区：
文献类型：
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作者：
M. Ouchi;Hiroaki Yoda;Takaya Terashima;M. Sawamoto
通过配基设计实现了催化水相活性自由基聚合。将酚性膦配体[PPh2(PPhOH)]与基于五甲基环戊二烯(CP*)的四聚Ru前驱体结合，在氯引发剂[H-(MMA)2-Cl]的配合下，对亲水性甲基丙烯酸酯(如聚甲基丙烯酸乙二醇酯和甲基丙烯酸羟乙酯)的水溶液活性自由基聚合表现出高催化活性。该催化体系允许非常快速的活性聚合、嵌段共聚和合成具有窄分子量分布的高分子量聚合物(DP n∼1000)。重要的是，即使聚合是在低温(40℃)下进行的，其活性也足够高，可以使用催化量的络合物来控制聚合。这种先进的催化作用不仅是通过配体的简单亲水性实现的，而且还通过水辅助的动态转化从最初的配位饱和形式[Cp*RuCl(PR 3)2；18e；PR 3=膦]转变为不饱和的活性形式[Cp*RuCl(PR 3)；16e]。水分子(S)也可以配位进一步稳定，如31P核磁共振分析所证明的那样。
Catalytic aqueous living radical polymerization was achieved through a ligand design for a ruthenium-based catalyst. A phenolic phosphine ligand [PPh 2 (pPhOH)] was combined with a pentamethylcyclopentadienyl (Cp*)-based tetrameric ruthenium precursor, and the resulting complex showed a high catalytic activity for aqueous living radical polymerizations of hydrophilic methacrylates (for example, poly (ethylene glycol) methacrylate and 2-hydroxyethyl methacrylate) in conjunction with a chlorine initiator [H–(MMA) 2–Cl]. The catalytic system allowed very fast living polymerizations, block copolymerizations and syntheses of high-molecular-weight polymers (DP n∼ 1000) with narrow-molecular-weight distributions. Importantly, the activity was high enough to control the polymerization using a catalytic amount of the complex, even though the polymerizations were performed at low temperature (40 C). Such advanced catalysis was achieved by not only simple hydrophilicity of the ligand but also by a water-assisted dynamic transformation from the original coordinatively saturated form [Cp* RuCl (PR 3) 2; 18e; PR 3= phosphine] into an unsaturated and active form [Cp* RuCl (PR 3); 16e]. Water molecule (s) may also coordinate for further stabilization as demonstrated by 31 P NMR analyses.