Abstract: An object of the invention is to provide a substance enabling uniformly dispersing an ionic liquid or a phosphonium salt in various solvents, resin materials, and the like. A powdery silica composite particle obtained by a surface treatment step comprising providing a reaction solution by mixing a silica sol containing a core silica particle having an average particle size of 5 to 200 nm, an alkoxysilane, and an ionic liquid and hydrolyzing the alkoxysilane by addition of an acid or an alkali to the reaction solution to surface-treat the core silica particle.

Abstract: A material enabling uniformly dispersing an ionic liquid or a phosphonium salt in various solvents or resin materials is provided. The material is powdery particles of a three-dimensionally crosslinked clathrate obtained by a process including a first-order polymerization step in which a fluoroalkanoyl peroxide compound, a monofunctional monomer, and a polyfunctional monomer having an olefinic double bond and an isocyanate group are reacted to one another to obtain a fluoroalkyl-containing cooligomer and a crosslinking step including the substeps of mixing the fluoroalkyl-containing cooligomer and an ionic liquid or a phosphonium salt and causing the cooligomer to react with itself at the isocyanate groups thereof in the presence of the ionic liquid or the phosphonium salt to obtain powdery three-dimensionally crosslinked clathrate particles.