A comparative study of the SET-LRP of oligo(ethylene oxide) methyl ether acrylate in DMSO and in H2O
A comparative study of the SET-LRP of oligo(ethylene oxide) methyl ether acrylate in DMSO and in H2O
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DOI：
10.1039/c2py20782f
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发表时间：
2013
影响因子：
4.6
通讯作者：
N. Nguyen;J. Kulis;Hao-Jan Sun;Zhongfan Jia;B. Beusekom;Martin E Levere;D. Wilson;M. Monteiro
中科院分区：
文献类型：
--
作者：
N. Nguyen;J. Kulis;Hao-Jan Sun;Zhongfan Jia;B. Beusekom;Martin E Levere;D. Wilson;M. Monteiro
本文报道了低聚(环氧乙烷)甲基醚丙烯酸酯(OEOMEA)在二甲基亚砜(DMSO)和水(25℃)中的SET-LRP的比较分析。活化的铜(0)丝/Me6-Tren和“初生”的Cu2+纳米粒子/Me6-Tren的催化剂在水中的聚合速率均高于在二甲基亚砜中的聚合速率。这一结果与SET-LRP在更极性的反应溶剂中预期的加速一致，也与CuBr在DMSO(Kd=1.4-4.4)和水(Kd=106-107)中歧化的平衡常数之差一致，在Me6-Tren存在下，两者都要高得多。Cu(0)催化剂对胶束结构中单体和引发剂疏水反应中心的访问效率低下，这解释了在水中观察到的OEOMEA的SET-LRP诱导时间。铜(0)丝的感应期较长。通过溴化亚铜在二甲基亚砜中的歧化反应制备的“新生”纳米铜(0)与5摩尔%的溴化铜相结合，在水中形成了一种非常有效的OOMEA的SET-LRP。SET-LRP在水中的反应速度快，单体转化率符合一级反应动力学，实验数据与转化率呈线性关系，分子量分布较窄。在水和DMSO中研究的聚合条件下，通过在线UV-Vis光谱观察到CuBr2/Me6-Tren的吸光度没有降低。这排除了在DMSO和水中的SET-LRP过程中，CuBr2被CuBr2还原而形成的CuBr2。
A comparative analysis of the SET-LRP of oligo(ethylene oxide) methyl ether acrylate (OEOMEA) in DMSO and in H2O at 25 °C is reported. Both the catalysis with activated Cu(0) wire/Me6-TREN and with mimics of “nascent” Cu(0) nanoparticles/Me6-TREN resulted in a higher rate of polymerization in water than in DMSO. This result is consistent with the acceleration expected for SET-LRP by a more polar reaction solvent, and with the difference between the equilibrium constants of disproportionation of CuBr in DMSO (Kd = 1.4–4.4) and in water (Kd = 106 to 107), both much higher in the presence of Me6-TREN. The inefficient access of the Cu(0) catalyst to the hydrophobic reactive centers of the monomer and initiator assembled in micellar structures explains the induction time observed in the SET-LRP of OEOMEA in water. This induction period is longer for Cu(0) wire. The use of “nascent” Cu(0) nanoparticles prepared by the disproportionation of CuBr in DMSO, in combination with 5 mol% CuBr2, led to an extremely efficient SET-LRP of OEOMEA in water. This SET-LRP in water is fast and follows first order kinetics to complete monomer conversion with linear dependence of experimental Mn on conversion, and narrow molecular weight distribution. Under the polymerization conditions investigated in both water and DMSO, no reduction in the absorbance of CuBr2/Me6-TREN was observed by online UV-vis spectroscopy. This excludes the formation of CuBr by reduction of CuBr2 by Cu(0) during the SET-LRP in DMSO and in water.