Dry grinding of polymer solids with silicananoparticles to give powdery nanocomposites: mechanochemical effect on thermotropic behaviour and solid-state dissolution of molecular crystals

Abstract

The dry beads grinding of polystyrene with surface-modified silica nanoparticles resulted in the formation of powdery nanocomposites. Molecular weights of the polymer were scarcely altered even after the grinding, indicating that the polymer exhibits resistance toward mechanochemical fission of main chains under the milling conditions. The procedure was applied to various types of polymers to give powdery nanohybrids, which are thought to be comprised of silica nanoparticles and polymer coils adhered on them. The nanopowders thus prepared gave slurries in water even in the absence of a surfactant, though the original polymeric powders were not dispersed in water at all. Particular events brought about by the milling caused the marked modification of thermotropic properties of polymer solids, implying the mechanochemically induced conformational alteration of polymer coils. As a result, pyrene crystals were able to be dissolved in polymer solids molecularly in a mechanochemical way under dry conditions, as evidenced by the generation of monomer emission.