Center for Macromolecular Engineering, Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA 15213, USA.
Science. 2011 Apr 1;332(6025):81-4. doi: 10.1126/science.1202357.
Atom transfer radical polymerization is a versatile technique for exerting precise control over polymer molecular weights, molecular weight distributions, and complex architectures. Here, we show that an externally applied electrochemical potential can reversibly activate the copper catalyst for this process by a one-electron reduction of an initially added air-stable cupric species (Cu(II)/Ligand). Modulation of polymerization kinetics is thereby tunable in real time by varying the magnitude of applied potential. Application of multistep intermittent potentials successfully triggers initiation of polymerization and subsequently toggles the polymerization between dormant and active states in a living manner. Catalyst concentrations down to 50 parts per million are demonstrated to maintain polymerization control manifested in linear first-order kinetics, a linear increase in polymer molecular weight with monomer conversion, and narrow polymer molecular weight distributions over a range of applied potentials.
原子转移自由基聚合是一种通用的技术，可以对聚合物的分子量、分子量分布和复杂结构进行精确控制。在这里，我们表明，外部施加的电化学电势可以通过初始添加的空气稳定的铜配合物（Cu（II）/配体）的单电子还原来可逆地激活该过程的铜催化剂。通过改变施加电势的大小，可以实时调节聚合动力学。多步间歇电势的应用成功地引发了聚合的开始，并随后以活的方式在休眠和活性状态之间切换聚合。证明催化剂浓度低至 50ppm 即可维持聚合控制，表现为线性一级动力学、聚合物分子量随单体转化率线性增加以及在一系列施加电势范围内聚合物分子量分布较窄。
