| Budget Amount *help |
¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1996: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Research Abstract |
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
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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
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