Abstract
Organic-inorganic hybrid network polymers have been synthesized by addition reaction of a thiol-functionalized random type silsesquioxane (SQ109) and alkyl diacrylate or diisocyanate compounds. Thiol-ene reaction of SQ109 and 1,4-butanediol diacrylate (BDA) successfully yield porous polymer in toluene initiated by azobis(isobutyronitrile) (AIBN) at 60°C. Morphology of the porous polymers was composed by connected globules, and the diameter of the globules decreased with increasing in the monomer concentration of the reaction system. By contrast, the reaction with 1,6-hexanediol diacrylate or 1,5-hexadiene yielded homogeneous clear gels. Thermal analyses of SQ109-BDA porous polymers indicated that thermal degradation of ester groups of BDA in the polymer network occurred at around 300°C. The porous polymer was also obtained by the reaction using a photo-initiator (Irugacure184) at room temperature, and showed higher Young’s modulus than the corresponding porous polymer obtained with the reaction with AIBN due to the small size of the globules. Young’s modulus of SQ109-BDA porous polymer increased with increasing in the monomer concentration of the reaction systems. Thiolisocyanate addition reactions between SQ109 and hexamethylene diisocyanate (HDI) or methylenediphenyl 4,4’-diisocyanate (MDI) were investigated to obtain network polymers. The reactions in toluene yielded the corresponding homogeneous clear gels. By contrast the reactions in a mixed solvent of toluene (50 vol.%) and N,N-dimethylformamide (50 vol.%) produced porous polymers. The morphology of the porous polymers was composed by connected globules or aggregated particles. The size of globules and particles in the SQ109-HDI porous polymers was larger than those in the SQ109-MDI porous polymers. Thermal degradation of SQ109-HDI and SQ109-MDI porous polymers started at round 260°C and showed endothermic peak at around 350°C derived from degradation of thio-urethane bond.
Highlights
Silsesquioxane is general term for materials, which are formed by Si-O back bone with (RSiO1.5)n composition
Figures 2(A)-(D) show Scanning electron microscopy (SEM) images of the dried SQ109-butanediol diacrylate (BDA) network polymers obtained from the reaction systems with different monomer concentrations
Organic-inorganic hybrid network polymers were synthesized by thiol-ene reaction or thiol-isocyanate reaction of a thiol-functionalized random type silsesquioxane, SQ109, and diacrylate, diolefin, or diisocynate
Summary
Silsesquioxane is general term for materials, which are formed by Si-O back bone with (RSiO1.5)n composition. Silsesquioxane is one of the most useful building blocks to obtain organic-inorganic hybrid polymers. There are some types of silsesquioxanes, such as cage (perfect, imperfect), random, and ladder, as shown in Scheme 1. The cage type silsesquioxanes have been widely used for synthesis of the hybrid polymers with network structure. We reported synthesis of gels by a hydrosliylation reaction of a perfect cage type silsesquioxanes, as a joint monomer, and α, ω-diolefin, as a linker monomer, using Pt catalysts in toluene, [1] [2] [3]. Addition reactions with multifunctional silsesquioxane and α, ω-bifunctional monomer, so called joint and liker concept, makes it possible to form network in the organic-inorganic hybrid gels with homogeneous structure, controlled mesh size, and designed molecular geometry
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