Poly (vinylidene fluoride)-based microcellular dielectrics filled with polydopamine coated carbon nanotubes for achieving high permittivity and ultralow dielectric loss

Abstract

Poly (vinylidene fluoride) (PVDF)-based microcellular dielectrics with polydopamine (PDA) coated carbon nanotubes (CNTs) were fabricated through scCO2 foaming technologies. Compared with pristine CNT/PVDF foam composites, the dielectric permittivity and loss factor of coated composites were much lower due to the significantly reduced polarizability within particle/polymer interfaces. Besides, these two parameters were also reduced with increasing expansion ratio, which was ascribed to the disaggregation of conductive particles and the increased air in the cells. Furthermore, it was demonstrated that more nucleation points initiated by the enlarged saturation pressure yielded the increased number of cells and the space restriction led to a mild growth of the cell size, which benefited for minimizing the increase of inter-particle spacing and the disentanglement between particles. Accordingly, the PDA@CNT/PVDF composites foamed to a high ER achieved a relatively large permittivity and an ultralow dielectric loss, which paved a new way to fabricate microcellular dielectrics.