Thermally activated tunneling in carbon nanotube carbon black hybrid nanofiller polymer nanocomposites: Influence of electronic subbands on thermoresistivity

The thermoresistive behavior of conductive polymer nanocomposites is critical for applications such as temperature sensors, thermistors, and self-regulating heaters. However, understanding how temperature influences charge transport in hybrid nanofiller systems remains challenging due to the complex interplay between matrix thermal expansion, filler geometry, and quantum tunneling. This study develops a simulation-based percolation model to investigate thermoresistivity in polymer nanocomposites containing carbon black (CB) and carbon nanotube (CNT) hybrid nanofiller. The aim is to quantitatively elucidate how temperature affects electrical resistivity by incorporating the key physical mechanisms governing thermally activated charge transport, including the temperature coefficient of resistance of conductive fillers, the thermal expansion coefficient of the polymer matrix, and temperature-dependent electron tunneling through electronic subbands. A major challenge addressed is the accurate representation of tunneling resistance as a function of temperature-dependent inter-filler distances, while accounting for confinement-induced electronic subbands in CB nanoparticles and CNTs. The model predicts that thermoresistivity increases with random nanofiller orientation and low CNT aspect ratios. Validation against experimental data reported in the literature demonstrates good agreement across a range of filler concentrations, and temperatures. The results further show that thermoresistivity can be systematically tailored by adjusting the CNT and CB properties, enabling the design of either temperature-stable conductive composites or highly sensitive thermoresistive materials.