Preparation of Inorganic/Organic Composite by Sol-Gel Process in the Presence of Polymer-Grafted Ultrafine Inorganic Particles and Its Solvent-Sensing Properties

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We examined the preparation of a novel inorganic/organic composite by sol-gel process in the presence of polymer-grafted inorganic ultrafine particles and the solvent-sensing properties of the composite in the various solvents. When sol-gel reaction of tetraethoxysilane was carried out in the presence of poly (N-vinyl-2-pyrrolidone)-grafted, and poly (2-methyl-2-oxazoline)-grafted carbon black, a deep black silica gel/carbon black composite in which carbon black particles were uniformly incorporated was obtained. The radical graft polymerizations of vinyl monomers onto the prepared composite surface was tried by use of radical initiators in the presence of the composite. During the polymerizations, part of the resultant vinyl polymers grafted onto the composite surface by the radical scavenging reaction of carbon black particles in the composite: the percentage of grafting was in the range of 3-8%. The solvent adsorption properties of the silica gel/carbon black composite varied with the solubility of grafted polymer chains on the carbon black surface and the composite surface toward the immersion solvent. In the case of the good solvent for both the grafted polymer chains of the carbon black surface and the composite surface, the silica gel/carbon black composite selectively adsorbed the solvent. Electric resistance of the polymer-grafted silica gel/carbon black composite was also very sensitive to the good solvent of the grafted polymer chains: the electric resistance drastically decreased in good solvent of both the grafted polymer chains of the carbon black surface and the composite surface, but it sparingly changed in poor solvent of the grafted polymer chains on both surfaces.