Fabrication and origin of asymmetric polyvinylidene fluoride-carbon nanotube/cyanate ester materials with high dielectric constant and low dielectric loss through building double-layered structure

High dielectric loss has been the biggest sticky problem for high-k conductor/polymer composites. Herein, a new asymmetric material consisting of one layer of β-phase poly(vinylidene fluoride) (PVDF) and another layer of carboxylated carbon nanotube (eCNT)/cyanate ester (CE) composite was fabricated, coded as PVDFx–eCNTq/CE, where x is the thickness of PVDF layer ranging from 3 to 70 μm, q is the loading of eCNTs (f), taking values of 1.2 and 1.7 wt%. The influences of f and x values on dielectric properties and breakdown strengths of PVDF–eCNT/CE materials were systematically studied. When f is smaller than the percolation threshold (fc) of eCNT/CE (fc = 1.6 wt%), the corresponding PVDF–eCNT1.2/CE materials have similar conductive and dielectric properties as eCNT1.2/CE composite. When f > fc, all PVDF–eCNT1.7/CE materials have much lower dielectric loss than eCNT1.7/CE, while with suitable thickness of PVDF layer (