Silica gels with various macropore structure due to phase separation were prepared by hydrolyzing alkoxysilane in the presence of nonionic surfactant, polyoxyethylene nonylphenyl ether. The gel phase was mainly composed of silica and the surfactant, whereas the fluid phase was mostly solvent. The pore volume of resultant gels increased with an increase of solvent fraction On the other hand, the domain size exhibited a maximum against the surfactant/silica ratio. These results were comparable to those obtained with polyethylene oxide) having the polymerization degree of a few hundreds, which suggests the postulation that decreased affinity of silica oligomer to the aqueous solvent due to the adsorption of oxyethylene units causes the phase separation.
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