We describe the influence of calcium copper titanate (CCTO) and montmorillonite (MMT) on the thermo-mechanical and dielectric properties of poly(methyl methacrylate) PMMA-based composites prepared by an in-situ thermally activated radical polymerization for multifunctional structural capacitor applications MMT was used for its ability to disperse and suspend the CCTO particles through the generation of viscous monomer slurries X-ray diffraction (XRD) measurements together with transmission electron microscopy (TEM) analysis revealed that the MMT platelets were present in both intercalated and exfoliated morphologies within the polymer matrix The filler addition was found to improve the thermal stability and the glass transition temperature of PMMA in the composites Furthermore the elastic stiffness and dielectric constant of the resultant composites were observed to increase monotonically with filler loading By contrast the dielectric breakdown strength of the composite samples was found to diminish with increasing filler loading (C) 2010 Elsevier Ltd All rights reserved