无水FeCl_3存在下丙烯酸甲酯的单电子转移活性自由基聚合动力学

单电子转移活性自由基聚合(SET-LRP)是一种可以对聚合物进行有效分子设计,合成不同拓扑结构并且能够有效调节其相对分子质量和相对分子质量分布的新型聚合方法,具有潜在的应用前景。以2-溴丙酸甲酯作为引发剂,Cu(0)/三(N,N-二甲基氨基乙基)胺(Me6-TREN)为复合催化体系,通过在二甲基亚砜中添加不同摩尔浓度的无水FeCl_3来研究其对丙烯酸甲酯的SET-LRP聚合动力学的影响。结果表明,随着三价铁离子量的增加,其链增长速率常数下降并且出现诱导期延长现象,说明三价铁离子参与了SET-LRP的聚合动力学过程,它和在同样实验条件下二价铜所起的作用截然不同,这可能是由于三价铁离子的氧化导致反应体系中一价铜的浓度降低引起的。此项工作从另外一个角度解释了零价铜催化下SET-LRP聚合诱导期产生的原因。

Kinetics of Single-Electron Transfer Living Radical Polymerization of Methyl Acrylate in the Presence of Anhydrous Ferric Chloride

Single-electron transfer living radical polymerization(SET-LRP) as an effective method is adopted to synthesize polymers with defined relative molecular mass, composition and specified molecular structure, which is powerful to adjust the molecular mass distribution of the obtained polymers in a wide range. To study the effects of the externally added anhydrous ferric chloride on the general SET-LRP polymerization kinetics of methyl acrylate, we carry out the research by using methyl 2-bromopropionate as the initiator and Cu(0)/tris(2-(dimethylamino)ethy)amine(Me₆-TREN) as the composite catalytic system in dimethyl sulfoxide with different ratios of anhydrous ferric chloride. The experimental results indicate that the externally added anhydrous ferric chloride has an important influence on the polymerization kinetics of methyl acrylate. With increasing the concentration of iron ions in the solvent, the polymerization rates decrease and the induction period appears to be prolonged indicating that iron ions are involved in SET-LRP polymerization kinetics. This may be due to the decreased concentration of Cu(Ⅰ) relative to that of the reaction without the addition of any anhydrous ferric chloride. The current work will stimulate us to further clarify the origin of induction period in the copper(0) catalyzed SET-LRP of typical monomers.