Preparation of Inorganic/Organic Nano Composite Sensor by Sol-Gel Process in the Presence of Both Recycled Polymers and Polymer-Grafted Carbon Nanotube

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We examined the preparation of a novel inorganic/organic nano composite by sol-gel process in the presence of both recycled polymers and polymer-grafted inorganic nano-particles, such as carbon black, carbon nanotube, and carbon microcoil. The surface grafting of polystyrene and polyester was achieved by use of hydroxyl groups on the nano-particle surface as initiating sites. When sol-gel reaction of phenyl-triethoxysilane was carried out in the coexistence of the polymer-grafted carbon black and carbon nanotube, and recycled polystyrene and poly(ethylene terephthalate), thin films of silica gel/inorganic nano-particle composite in which both the inorganic nano-particles and recycled polymers were uniformly incorporated were obtained. We examined also the vapor-sensing properties of the composites in the various solvents in order to apply these composites to a novel vapor sensor. The vapor adsorption properties of the silica gel/carbon black composite varied with the solubility of grafted polymer chains on the carbon black surface and the recycled polymer chains toward the applied solvent. In the case of the good solvent for both the grafted polymer chains of the carbon black surface and the recycled polymer chains, the silica gel/carbon black composite selectively adsorbed the solvent vapor. Electric resistance of the composite was also very sensitive to the vapor of the good solvent for the grafted and recycled polymer chains: the electric resistance drastically decreased in vapor of good solvent for both the grafted polymer chains of the carbon nanotube surface and the recycled polymer chains, but it sparingly changed in vapor of poor solvent for both of them.