Development of New Synthetic Methodology for Polymers with Controlled Molecular Weight Using Metalloporphyrins as Initiators

本研究以金属卟啉为引发剂，开发了一种新的、具有广泛适用性的分子量可控聚合物的合成方法。铝卟啉是具有代表性的引发剂，能有效地引发环氧化物、内酯、丙交酯等杂环单体和甲基丙烯酸、丙烯酸酯、甲基丙烯酸乙酯等乙烯基单体的活性聚合，得到分子量可控、分子量分布窄的聚合物。环氧化物与二氧化碳或环酸酐的活性交替共聚也可以使用铝卟啉作为引发剂，并与季铵盐偶联。机理研究表明，所有这些聚合都是在中心铝上进行的。引发剂的原子轴向配位键。值得注意的是，一些上述聚合反应被卟啉lig…的光激发极大地加速更多的是用可见光。N-取代卟啉的锌配合物对环氧化物和环硫醚(三元环硫醚)的活性聚合也是有效的，前者为可见光诱导活性聚合提供了一个新的例子。通过利用金属卟啉作为活性聚合引发剂的广泛适用性，合成了各种嵌段长度均匀、可控的嵌段共聚物。更值得注意的是发现了永生聚合这一新概念，它优于活性聚合，因为永生聚合能够合成具有窄分子量分布的聚合物，其聚合物分子的数量多于引发剂分子的数量。不朽聚合是设计分子量均匀的末端官能化(末端反应性、末端可聚合性、遥距螺旋和星形)聚合物和低聚物的有效方法。除了铝和锌的卟啉外，锰卟啉也是环氧化物不朽聚合的有效引发剂。较少

The present research project has developed a novel, widely applicable synthetic methodology for polymers with controlled molecular weight by using metalloporphyrins as initiators. Aluminum porphyrins are the representative initiator, which bring about effectively the living polymerizations of heterocyclic monomers such as epoxides, lactones and lactide, and vinyl monomers such as methacrylic and acrylic esters and methacrylonitdle, affording the polymers of controlled molecular weight with narrow molecular weight distribution. Living, alternating copolymerizadon of epoxides with carbon dioxide or cyclic anhydride is also possible using aluminum porphyrin as initiator coupled with quaternary onium salts. Mechanistic studies have demonstrated that all these polymerizations proceed at the central aluminum. atom axial ligand bond of the initiator. It should be of interest to note that some of the above polymerizations are dramatically accelerated by the photoexcitation of the porphyrin lig … More and with visible light. Zinc complexes of N-subsdtuted porphyrins are found also effective for the living polymerizations of epoxides and episulfides (three-membered cyclic thioethers), where the former case has provided a novel example of visible light-induced living polymerization. By taking advantage of the wide applicability of metalloporphyrins as initiators for living polymerizations, a variety of block copolymers with uniform, controlled block lengths have been synthesized. Of further interest to note is a discovery of the new concept, immortal polymerization, which is superior to living polymerization in the sense that immortal polymerization enables the synthesis of polymers with narrow molecular weight distribution with the number of the polymer molecules more than that of the initiator molecules. Immortal polymerization is very effective for molecular design of terminally functional (end-reactive, end-polymerizable, telechelic, and star-shaped) polymers and oligomers with uniform molecular weights. In addition to aluminum and zinc porphyrins, manganese porphyrins are also effective as initiators for the immortal polymerization of epoxides. Less