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research papers
Small-angle X-ray scattering was used to study structural modifications in tetraethoxysilane-derived poly(vinyl alcohol) (PVA)/silica hybrids. The basic structure of the wet gels can be described as a mass-fractal structure with fractal dimension D equal to 2 and characteristic length ξ, which increases with addition of PVA. Wet gels with high PVA content exhibit a positive deviation from the mass-fractal power-law scattering at low q; this deviation is associated with additional scattering due to a second large correlation distance ζ, reinforced by the addition of PVA. The fraction of both contributions to the total correlation function was estimated; this is the first time that such a study has been carried out for mass-fractal structures.