Multiple-length-scale small-angle X-ray scattering analysis on maghemite nanocomposites.

Small-angle X-ray scattering (SAXS) analysis has been performed on maghemite-poly(4-vinylpyridine) nanocomposites prepared by in situ precipitation from iron-polymer coordination compounds. According to electron microscopy observations, the nanocomposites contain isolated spherical particles with a narrow size distribution, uniformly distributed throughout the polymer matrix. The scattering intensity of nanocomposites has relevant contributions from both the polymer and the nanocomposites, showing features characteristic of multiscale structured systems, namely two power laws and a Guinier regime. The data have been analysed in terms of Beaucage’s unified approach and it is found that the maghemite particle size increases with the iron/polymer weight ratio used in the preparation of the nanocomposites. SAXS curves also feature a bump that was analysed as arising from a second particle population or from interactions. Magnetization and transmission electron microscopy results give arguments favouring the latter interpretation. It is found that the maghemite particle sizes vary linearly with the iron weight ratio used in the preparation of the nanocomposites.