Synthesis, characterization and reinforcing properties of novel, reactive clay/poly(glycidyl methacrylate) nanocomposites

Clay/polymer nanocomposites, of the type montmorillonite/poly(glycidyl methacrylate) [MMT/PGMA], were synthesized via atom transfer radical polymerization (ATRP). An ATRP initiator, consisting of quaternary ammonium salt bearing a 2-bromo-2-methyl propionate moiety was intercalated into the interlayer spacings of the layered silicate. The ammonium salt-modified montmorillonite (MMT–Br) served as macroinitiator for the in situ ATRP of glycidyl methacrylate resulting in highly exfoliated MMT/PGMA nanocomposites, as judged by XRD measurements. However, TEM shows the existence of intercalated clay regions, but at a very low extent. TGA and XPS analyses indicate that the nanocomposites have PGMA-rich bulk and surface. Indeed, the mass loading of PGMA reached 61 wt.% whilst XPS spectra, particularly the high resolution C1s region, resemble those of pure PGMA. The MMT/PGMA nanocomposites were found to be soluble in chloroform with a transparent solution, fully compatible with epoxy resin without any sign of phase separation. The primary MMT/PGMA nanocomposites were mixed with DGEBA and DETA in chloroform in order to prepare moulded, ternary MMT/PGMA–epoxy–DETA nanocomposites by solvent evaporation. The dried ternary systems exhibited superior viscoelastic properties (storage modulus and tan δ) compared to the neat crosslinked epoxy–DETA adhesive prepared in the absence of any clay nanocomposite.