| Budget Amount *help |
¥31,600,000 (Direct Cost: ¥31,600,000)
Fiscal Year 1989: ¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1988: ¥7,300,000 (Direct Cost: ¥7,300,000)
Fiscal Year 1987: ¥22,300,000 (Direct Cost: ¥22,300,000)
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| Research Abstract |
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
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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
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