Design, Development and Industrial Applications of Latent Polymerization and Curing Catalysts

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Previous research on the latent polymerization catalysts focused on the design and synthesis of various onium salts such as phosphonium, pyridinium and sufonium salts as well as evaluation of their activity as latent catalysts. This is simply because of the facility of their preparation and in the control of the activity by modifying their substituents. However, low solubility of onium salts in organic solvents or monomers and inorganic residue in polymers or resigns often cause serious problems in the practical usage. Additionally, the monomers which can be polymerized by the previously reported catalysts are limited to cationically polymerizable monomers such as epoxides and vinyl ethers.The motivations of this research include the development of 1) non-salt type latent polymerization catalysts with high solubility ans latency, and 2) novel latent catalysts which are active for anionic polymerization of electrophilic monomers. As results, several carboxylates and sulfonates were found to serve as non-salts-type latent catalysts for the polymerization of substituted epoxides and vinyl ethers. Anionic polymerization of epoxides was also possible by using aminimides as a latent polymerization catalyst. The aminimides exhibited typical behavior as latent polymerization catalysts, no activity was observed below 80ﾟC whereas they works as initiator by heating above 100ﾟC.The initiation mechanism of the aminimide-induced polymerization involves the thermal decomposition of the catalyst into isocyanates along with the formation of tertiary amines which serves as a initiation species. We also succeeded in the preparation of aminimide with hydroxyl group which serves as a novel "latent monomer" by heating, leading to the formation of polyurethanes or pplyureas.