Photocontrolled living polymerizations
Photocontrolled living polymerizations
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DOI：
10.1038/nmat1649
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发表时间：
2006-06
期刊：
影响因子：
41.2
通讯作者：
M. Tanabe;Guido W. M. Vandermeulen;Wing Yan Chan;P. W. Cyr;Lawrence Vanderark;D. Rider;I. Manners
中科院分区：
文献类型：
--
作者：
M. Tanabe;Guido W. M. Vandermeulen;Wing Yan Chan;P. W. Cyr;Lawrence Vanderark;D. Rider;I. Manners
活性聚合涉及在没有显著的不可逆链转移或链终止的情况下产生聚合物链。这种方法广泛用于获得具有受控结构的明确定义的大分子材料，例如嵌段和星星聚合物。虽然这一概念在20世纪50年代首次在阴离子聚合中实现，但最近已经取得了许多关键进展，最值得注意的是在自由基聚合领域。在这里，我们报告了一个活的光聚合，涉及光激发单体。在阴离子引发剂的存在下，将含金属的二茂铁单体暴露于来自汞灯的Pyrex过滤光（λ>310 nm）或暴露于明亮的阳光导致活性聚合，其中所得聚合物的转化率和分子量可以通过照射时间来控制。光辐射选择性地削弱单体中的铁-铁键，允许使用中等碱性和高度官能团耐受的引发剂。聚合反应是通过引发剂的攻击和阴离子在光激发单体的铁原子上的传播来进行的，并且，值得注意的是，聚合速率随着温度的升高而降低。当光源在不同单体的顺序添加之间交替地打开和关闭时，嵌段共聚物的形成是可能的，从而提供了前所未有的、光控的新型功能聚合物。
Living polymerizations involve the creation of polymer chains without significant irreversible chain transfer or chain termination. Such processes are widely used to access well-defined macromolecular materials with controlled architectures, such as block and star polymers. Although this concept was first realized for anionic polymerizations in the 1950s, many key recent advances have been made, most notably in the area of radical polymerization,,,. Here, we report a living photopolymerization that involves photoexcited monomers. Exposure of metal-containing ferrocenophane monomers to Pyrex-filtered light from a mercury lamp (λ>310 nm) or to bright sunlight in the presence of an anionic initiator leads to living polymerizations, in which the conversion and molecular weight of the resulting polymer can be controlled by the irradiation time. Photoirradiation selectively weakens the iron–cyclopentadienyl bond in the monomer, allowing the use of moderately basic and highly functional-group-tolerant initiators. The polymerization proceeds through attack of the initiator and propagating anion on the iron atom of the photoexcited monomer and, remarkably, the polymerization rate decreases with increasing temperature. Block copolymer formation is possible when the light source is alternately switched on and off in between sequential addition of different monomers, providing unprecedented, photocontrolled access to new types of functional polymers.