Study on frequency-dependent complex permittivity of GNPs/polymer nanocomposites with poor dispersion phenomenon

Graphene nanoplatelets (GNPs)/polymer nanocomposites have received great interests in multi-function composite structures due to their excellent performances, such as the dielectric permittivity, the mechanical properties, etc. The non-uniform distribution configuration of GNPs within the polymer matrix, also known as the poor dispersion phenomenon, is still considered to be unavoidable and plays an important role in determining the performances of the nanocomposites. However, the available theoretical models on predicting the dielectric permittivity of the nanocomposites seldom consider the poor dispersion phenomenon of GNPs. Firstly, this study develops a non-uniformly distributed model characterizing the poor dispersion features of GNPs. Then a multi-scale theoretical model for predicting the complex dielectric permittivity of the nanocomposites is proposed by combining the frequency-dependent analysis theory and the effective-medium approximation theory. To verify the effectiveness of the presented theoretical model, the complex dielectric permittivity of GNPs/Polyvinylidene Fluoride (PVDF) nanocomposites are analyzed and good agreement is obtained between the predicted values and the available experimental results. Discussion shows that the poor dispersion phenomenon of GNPs obviously affects the complex permittivity of nanocomposites. The study provides a highly efficient theoretical method and contributes to conducting the optimization design of the frequency-dependent complex permittivity of GNPs/polymer nanocomposites.