Complex formation of montmorillonite clay with polymers. Part 2: The use of montmorillonite clay-vinyl monomer complex as a comonomer in the copolymerization reaction of styrene-acrylonitrile monomers

The bulk copolymerization of styrene-acrylonitrile monomers using styrene-N⁺-montmorillonite complex as a comonomer in the polymerization was studied. The X-ray diffraction (XRD) analysis showed that part of the styrene-N⁺-montmorillonite complex remained non-dispersed (immiscible) and the copolymer was excluded from the interlayer of the immiscible part of the clay. The successive chemical extraction process revealed that a reasonable amount of the styrene-acrylonitrile copolymer was directly attached to the styrene-N⁺-montmorillonite complex and enveloped the clay. Highly exfoliated clay lamella and nanospheres (3-5nm) were observed by transmission electron microscopy (TEM). The montmorillonite clay assume two different morphologies, immiscible and exfoliated, on the basis of the XRD and TEM data. A simple method of calculation of the ratio of the exfoliated/immiscible amounts of the clay indicated that the amount of the styrene-N⁺-montmorillonite complex exfoliated into separate lamella was 40% (w/w) of the amount of the clay samples containing 2% of the (styrene-N⁺-montmorillonite complex) clay. This amount of exfoliated clay decreases with the increase of the concentration of the clay. The presence of the styrene-N⁺-montmorillonite clay in the copolymerization reaction had a minor effect on both the copolymer composition and the molecular weight. Modification of the clay with the derivatized styrene monomer can achieve a nanocomposite using a percentage no more than 4% (w/w) of complex in the copolymer.