Methods for dispersing of the thermally expanded graphite (TEG) in a dilute alcohol medium and for modifying the surface of a TEG with an ultradisperse dielectric - silicon dioxide (SiO2) are proposed. The new polymer nanocomposites (PNC) obtained based on polychlortrifluoroethylene (PCTFE) with a low content of dispersed TEG and a modified filler TEG/SiO2 are characterized by high rates of electrophysical properties. Using electron microscopy and X-ray photoelectron spectroscopy, the features of the electronic structure of the surface of composites are investigated. Using the two-contact method in the kilohertz frequency range, the features of change in the electrophysical properties of composites depending on the content of fillers and temperature have been established. Based on research and comparative analysis of thermophysical properties (specific heat capacity cp, temperature coefficient of linear expansion α) of the systems, the influence of the structural-morphological state of the components and their concentration, the level of interfacial interaction on the physical properties of nanocomposites was investigated. The fact of the appearance of interfacial polarization in the PCTFE-TEG/SiO2 interfacial layers due to the appearance of the TEG/SiO2 and PCTFE-SiO2 interphase layers is established, which, while preserving the complex of properties inherent to the polymer materials, increases the overall electrical conductivity of the composites. It was also established that the modified nanofiller exhibits greater activity in relation to the polymer matrix than the unmodified one. It is shown that the composites exhibit a dual effect of the modified nanofiller on the matrix structure, which manifests in the formation of a powerful crystalline structure in the zones of influence of the nanofiller and amorphization of the polymer matrix in the peripheral zones. It was found that the result of amorphization of the matrix is a decrease in the area of the peaks of temperature reflexes on the temperature dependences of the specific heat capacity and an increase in the absolute value of the temperature coefficient of linear expansion with an increase in the concentration of modified TEG.