Polymer-clay nanocomposites: Free-radical grafting of polystyrene on to organophilic montmorillonite interlayers

Abstract

Vinyl monomer-montmorillonite intercalates, which are able to swell and disperse in organic solvents, have been prepared by a cation exchange process by the interaction between the Na⁺ or Ca²⁺ cations of montmorillonite and vinylbenzyltrimethylammonium chloride. The resulting vinyl monomer-montmorillonite materials have been identified by X-ray diffraction (XRD), elemental analysis and infrared absorption spectra. Free-radical solution polymerizations of the penetrated styrene between the interlayers of 5, 10, 25 and 50 wt% vinyl monomer-montmorillonite have resulted in grafted polystyrenemontmorillonite materials. The effect of montmorillonite amounts on the formed polystyrene was determined by extraction with organic solvents, which showed an increase in the grafted polymer formed (0.84–2.94 g/g MMT), and a decrease in the external polystyrene with increasing amounts of montmorillonite. The molecular weight of the external polystyrenes was found to be in the range of 22000. The vinyl monomer-montmorillonite and polymer-montmorillonite intercalates have been identified by XRD, elemental analysis and infrared spectroscopy. Examination of the polystyrene-montmorillonite materials by SEM, TEM and XRD showed spherical particles of nanosize about 150–400 nm, and basal spacings of 1.72–2.45 nm.