DEVELOPMENT AND APPLICATIONS OF HIGH-SPEED LIVING AND IMMORTAL POLYMERIZATIONS

合成分子量均匀、可控的聚合物是聚合物化学领域的重要课题之一。我们发现，一些金属卟啉是各种单体活性和不朽阴离子聚合的良好引发剂。高速活性聚合是由铝卟啉(1)作为亲核引发剂与大体积路易斯酸(2)通过配位作用作为单体激活剂来实现的。在这样一个亲核-亲核共存的体系中，这两个物种之间的降解性中和很可能导致聚合的终止。然而，这种不受欢迎的反应被引发剂中的卟啉配体和Lewis酸中的大体积酚酸配体之间的空间斥力所抑制。这就是高速活性聚合的原理。高速活性聚合可以应用于甲基丙烯酸酯类…等单体更多的是丁腈、环氧化物、内酯和环碳酸酯。通过改变单体与引发剂的摩尔比，可以很好地控制聚合物的相对分子质量，在优化的条件下可以得到相对分子质量为&10^6的窄MWD聚合物。在手性Lewis酸存在下，外消旋的α-甲基苄基甲基丙烯酸铝卟啉催化的甲基丙烯酸外消旋活性聚合是由于单体的立体选择性活化而进行的。已被理解为仅以阳离子方式聚合的氧杂环己烷，也可通过目前的二元体系聚合，提供窄MWD聚醚。通过甲基丙烯酸甲酯和氧杂环己烷的连续高速活性聚合，成功地合成了一种新型的窄分子量分布的聚乙烯-聚醚嵌段共聚物。环氧化合物在铝卟啉/醇体系中的不朽聚合也被大体积的路易斯酸加速，在合适的条件下，每个引发剂分子可以得到1000多个窄分子量分布的聚合物分子。较少

Synthesis of polymers with uniform, controlled molecular weight is one of the important subjects in the field of polymer chemistry. We have found that some metalloporphyrins serve as excellent initiators for the living and immortal anionic polymerizations of a variety of monomers.High-speed living polymerization is realized by, e.g., aluminum porphyrins (1) as nucleophiric initiators in conjunction with bulky Lewis acids (2), which function as monomer activators through coordinative interaction. In such a nucleophile-electrophile coexisting system, a degradative neutralization between these two species, leading to termination of polymerization, is very likely to occur. However, this undesired reaction is suppressed by the steric repulsion between the porphyrin ligand in the initiator and the bulky phenolate ligands in the Lewis acids. This is the principle of the high-speed living polymerization.The high-speed living polymerization can be applied to monomers such as methacrylic esters … More and nitrile, epoxides, lactones, and cyclic carbonates. By changing the monomer-to-initiator mole ratio, molecular weight of the produced polymer is nicely controlled, where a narrow MWD polymer with a molecular weight >10^6 can be obtained under optimized conditions. The high-speed living polymerization of racemic alpha-methylbenzyl methacrylate by an aluminum porphyrin in the presence of a chiral Lewis acid proceeds enantioselectively as a result of the stereoselective monomer activation. Oxetane, which has been understood to polymerize only cationically, is also polymerizable by the present binary system, affording a narrow MWD polyether. Sequential high-speed living polymerization of methyl methacrylate followed by oxetane is successful to give a novel polyvinyl-polyether block copolymer with a narrow MWD.Immortal polymerization of epoxides by aluminum porphyrin/alcohol systems is also accelerated by bulky Lewis acids, and, under suitable conditions, more than 1000 polymer molecules with narrow MWD can be obtained per one initiator molecule. Less