STRUCTURE AND MORPHOLOGY OF SOL-GEL PREPARED POLYMER-CERAMIC COMPOSITE THIN-FILMS

Poly(p-phenylene vinylene) (PPV)-silica composite thin films were prep ared via the sol-gel process incorporating a water-soluble PPV precurs or. After solvent evaporation, the spin-coated or quiescently cast fil ms were cured and the PPV precursor and the silica sol were completely converted into the PPV-silica composites. Quiescently cast films show an improved wave-guiding behaviour with a chi3 value only slightly sm aller than pure PPV films. Their structure consists of a nanophase-sep arated morphology composed of amorphous silica and paracrystalline PPV . Small-angle X-ray scattering and bright field transmission electron microscopy images indicate a random arrangement of the nanoscale domai ns with average domain size of approximately 4 nm. In contrast, spin-c oated films show clusters and cluster-cluster aggregates approximately 100 nm in diameter. The clusters consist of particulate silica and po res, each about 3 nm in size, with the PPV contained in the pores and between the clusters. The observed morphologies are related to film pr eparation conditions in terms of sol-gel processing, taking the presen ce of the polymer into account.