AN ORGANIC-INORGANIC SINGLE-PHASE COMPOSITE

A composite of essentially equal volumes of poly(ethyloxazoline) and silica was prepared by hydrolyzing the silica precursor tetraethyl orthosilicate in a solution of the polymer in an organic solvent. Characterization by several instrumental and chemical techniques indicated that the composite consisted of only one phase. From this evidence we conclude that it was a molecular semi-interpenetrating network. In composites made with other ratios of these components, some characteristics changed abruptly as silica content was increased from <15 to >25 volume %. We postulate this concentration range to be the silica percolation threshold. A sharp increase in surface area above similar to 85 volume % silica is interpreted to reflect the presence of insufficient polymer to fill the voids normally found in silica made by the sol-gel technique.