Variety of composite materials has been developed so far, but in many cases trade-off of the functions are of important issues: fabrication becomes difficult due to the significant increase of viscosity, and transparency of the polymer is sacrificed. To over come the trade off, controll of the nano-interface is the key, but nanoparticles are easily aggregated in polymer matrix because of the higher surface energy of NPs, and thus it has been considered a difficult task. Organic functionalization of inorganic nanoparticles is required to have higher affinity between NPs and polymers. The organic modification, NPs should be dispersed in an organic solvent with high concentration, which is difficult. For fabricating multi-functional materials, we proposed a new method to synthesize organic modified nanoparticles (NPs) in supercritical water. Since the organic molecules and metal salt aqueous solutions are miscible under the supercritical state, and water molecule works as an acid/base catalyst for the reactions, organic-inorganic conjugate nanoparticles can be synthesized under the condition. The hybrid NPs show high affinity with the organic solvent or the polymer matrix, which leads to fabricate the organic inorganic hybrid nanomaterials with the compatible (trade-off) functions.
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