In this paper, we report the synthesis of networked polymers based on reductive coupling of carbodiimide by samarium(II) diiodide (SmI₂). First, reductive coupling of 1,3-di-p-tolylcarbodiimide (DTC) by SmI₂ was investigated as a model reaction. As a result, we found that DTC was reductively coupled by SmI₂ to give the corresponding oxalic amidine derivative. On the basis of the result, we synthesized carbodiimide-containg polymers by radical homopolymerization of N-(p-vinylphenyl)-N’-phenylcarbodiimide (VPPC) and its copolymerization with styrene and performed the network formation of the obtained polymers by reductive coupling of carbodiimide moieties in the side chain by SmI₂. The obtained networked polymers were found to have oxalic amidine structures in the linkage moiety by IR analysis.

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In the field of electrical equipments, unsaturated polyester resins and vinyl ester resins are widely used as adhesives and insulators. As a part of high-performing of thermosetting resins, we attempted thermostability improvement of them. In the case of thermosetting resins cured by radical polymerization, thermal decomposition occurs from vinyl groups derived from disproportionation reaction. It is known that the living radical polymerization inhibits the disproportionation reaction, thus we attempted to use living radical polymerization to improve thermostability of the resins. The thermal decomposition temperature of the resin cured by alkyl borane was higher than that cured by peroxide. Furthermore, the glass-transition temperature of the resin cured by the alkyl borane was higher than that cured by peroxide. From these results it was revealed that living radical initiator is a very effective reagent to improve thermostability of thermoset resins.

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A novel surface treatment method of ZrO₂ nanoparticles with 8 nm in a diameter and their hybridization with polymers have been studied to prepare the transparent organic－inorganic nano-hybrid materials. The surface treatment was achieved by direct transfer of ZrO₂ nanoparticles from aqueous phase to toluene phase without any coagulation. The method was successfully attained by adding small amount of carboxylic acid as the surface treatment agent, toluene, and methanol to ZrO₂ aqueous dispersion, followed by successive evaporations and solvent replacements to toluene dispersion. Transparent ZrO₂ toluene dispersion was obtained, when adding the carboxylic acids with the number of carbon atom higher than 4. The surface modified ZrO₂ particles were nano-dispersible into several organic solvents and vinyl monomers to afford transparent solutions. Methacrylate-functionalized ZrO₂ nano-particles were copolymerized with styrene or methyl methacrylate to produce optically transparent thermosetting nano-composite materials with a refractive index much higher than the original polymer. The network structures produced by copolymerization of vinyl monomer with methacrylate-functionalized ZrO₂ nano-particles as multivinyl crosslinking agent play an important role to prevent the coagulation of ZrO₂ particles.

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We have designed and synthesized a dimethacrylate containing a chalcone moiety. A novel hybrid UV curing system using photo-radical polymerization of methacrylates and photodimerization of chalcone was devised using the monomer. The mixture of the monomer, 2-ethylhexyl methacrylate as a diluent, and photoinitiators placed between two CaF₂ plates was irradiated at UV light (wavelength: 254, 365, 405 nm and 370 <λ< 400 nm) to investigate the effect of initiators or irradiation wavelength on the conversion of the methacrylate unit and the chalcone unit was investigated using UV and FT －IR spectroscopy. We have found that the conversion of the methacryl unit and the chalcone unit was controllable by the irradiation wavelength and initiators added. The effect of atmosphere in the system was slightly observed. The mixture of the monomer and 2-ethylhexyl methacrylate was photopolymerized without an initiator. The result suggests the possibility of a novel photoinitiating system using a chalcone moiety.

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For the development of adhesives for semiconductor packages, precise design of glass transition temperature of both uncured and cured resin is necessary. Glass transition is not thermo-dynamical phase transition, but a relaxation phenomenon. The general law of relaxation time is acquired from dispersion map of several organic glass-forming substances. The law is effective to estimate glass transition temperature measured by different frequency.

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In the toughening studies of cured epoxy reins, using reactive liquid rubbers as a modifier has been extensively investigated, and is commonly used in various industrial fields. We have been studying the relationship between the structure and physical properties of the polyurethane elastomers. One of the characteristics of the polyurethanes, it is possible to satisfy the required properties by any combinations of soft and hard segments in polyurethanes. In addition, polyurethanes can be prepared from soft gel to resins with a high elasticity. For preparing the polyurethane-modified epoxy resins, we have proposed a method for synthesizing by the in-situ polymerization of polyurethanes in epoxy resins. The studies of the relationship between morphology and physical properties of various modified epoxy resins prepared using this method are described.

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