Percolation Behavior of Electrical Conductivity of Polylactic Acid-Based Nanocomposites

This study investigates the electrical conductivity characteristics of polymer nanocomposites based on a polylactic acid matrix with the addition of carbon nanotubes (CNTs) were investigated using the impedance spectroscopy method. This approach allowed us to analyse the frequency dependences of electrical conductivity and identify the features of the percolation behavior of the studied systems. The results revealed that the electrical conductivity of the composites demonstrates a typical alternating current character: maintaining a constant value at low frequencies with a subsequent increase when reaching a critical frequency, which indicates a change in the charge transfer mechanism. A study of the influence of the CNT concentration on the electrical characteristics of the composites showed the presence of a clearly pronounced percolation threshold, which corresponds to the formation of a continuous network of conductive particles inside the polymer matrix. The data enabled a quantitative description of this transition using models of the critical percolation theory. It was found that even at low concentrations of CNTs (~ 0.5 %) there is a sharp increase in conductivity, which indicates the efficiency of nanotube dispersion in the polymer. Special attention was paid to modelling the frequency dependence of conductivity using Jonscher's law, which allowed us to establish a change in the nature of the interaction between charge carriers and the medium as the concentration of CNTs increases. Analysis of the parameter n demonstrated the presence of anomalous values that are not explained by classical conductivity models and indicate complex charge transfer processes associated with the formation of fractal-like topology or manifestations of anomalous diffusion. The results obtained are consistent with modern theoretical concepts of electrical conductivity in complex disordered systems. The study contributes to a deeper understanding of the mechanisms of electrical conductivity in polymer-CNT nanocomposites, which is of great importance for the further development of composite materials with controllable electrophysical properties optimized for specific functional applications.