Poly(methyl methacrylate) (PMMA)/montmorillonite (MMT) nanocomposites were prepared by a new one-pot technique, where the hydrophilic Na-MMT layerswere decorated with hydrophobic 1-dodecyl-3-methylimidazolium hexafluorophosphate
(C12mimPF6) ionic liquid in situ duringmelt blending with PMMA and intercalation of polymer chains took place subsequently. The in situ modification and intercalation of Na-MMT were confirmed using X-ray diffraction and transmission electron microscopy. The combination of the compatible C12mimPF6 withPMMAand the good dispersion ofMMTlayers at the nanoscale rendered the resultant PMMA/MMT nanocomposites with improved optical transparency, thermal stability and mechanical properties.