Tuning the AC electric responses of decorated PDA@MWCNT/PVDF nanocomposites

While the extraordinary electric behaviors of low-dimensional nanocomposites are widely known, the tunable effects induced by the decorated coating process still remains a challenging issue. In this research, a hierarchical model is established to quantitatively evaluate the tunable AC electric responses of decoration-coated CNTs in PDA@MWCNT/PVDF nanocomposites. First, a multi-scale geometric configuration is set up for the PDA@MWCNT/PVDF nanocomposites to clarify the coating microstructure of hollow CNTs with decorative interphase. Next, various functionalized interface effects between the constituents are revealed by the decoration-dependent tunneling distance, electron hopping time, and relaxation time of dielectrics. Then, the effective AC conductivity, permittivity, and dielectric loss of decorated PDA@MWCNT/PVDF nanocomposites are calculated through a combined effective-medium approximation and Mori-Tanaka method. The established theory is calibrated with the experiments in PDA@MWCNT/PVDF nanocomposites within a wide range of decoration thickness and frequency spectrum. The decoration thickness is found to increase nonlinearly with respect to the manufactured decoration/CNT mass ratio. It is demonstrated that the decorated interphase can significantly reduce the dielectric loss of the decorated nanocomposites while ensuring a relatively high dielectric constant by suppressing the leakage current at the interface.