Chemically derivatized graphene/poly(vinyl alcohol) (PVA) nanocomposites were successfully fabricated by combination of solution processing and compression molding. SEM imaging combined with XRD measurements revealed that graphene platelets were fully incorporated into the polymer matrix after their chemical modification through adsorption of amphiphilic copolymer. The chemical functionalities onto the graphitic surface prevented particle aggregation and provided compatibility with the polymer matrix. Thermogravimetric analysis demonstrated enhanced thermal stability for the composites containing modified graphenes at loading above 1 wt%. Differential scanning calorimetry thermograms showed that graphene nanoplatelets induced the crystallization of matrix with optimum loading at 2 wt%. Dielectric spectroscopy measurements showed enhanced electrical permittivity for the graphene oxide/PVA system, compared to the one of graphene/copolymer/PVA. This could be attributed to the formation of an insulating coating between graphite inclusions and PVA because of the presence of the copolymer

Polymer matrix-TiO2 composites were prepared in three different filler concentrations. The electrical relaxation dynamics as well as the electrical conductivity of all samples were examined by means of Broadband Dielectric Spectroscopy (BDS) over a wide frequency and temperature range. The recorded relaxation response includes contributions from both the polymer matrix and the reinforcing phase. Two relaxation modes (β and γ) are observed in the low temperature region, which are attributed to the re-orientation of polar side groups of the matrix and rearrangement of small parts of the polymeric chain respectively. The α-relaxation and the Maxwell-Wagner-Sillars effect (MWS), attributed to the glassrubber transition of the polymeric matrix and to interfacial polarization phenomena respectively, are observed in the high temperature region. These two mechanisms are superimposed, thus a computer simulation procedure was followed in order to distinguish them. MWS effect becomes more pronounced with increasing concentration of the filler following an Arrhenius behaviour. The relaxation frequencies corresponding to α-mode follow the Vogel-Tamann-Fulcher (VTF) equation. An additional relaxation mode is recorded at relatively high temperatures and high frequencies. Its occurrence and dynamics are related to the presence and the concentration of the filler. Finally, the Direct Current (DC) conductivity follows the VTF equation