Enhanced dielectric performance in flexible MWCNTs/poly(vinylidene fluoride-co-hexafluoropropene)-based nanocomposites by the design of tri-layered structure

Polymer composites with high permittivity are promising applications in advanced electronics. However, it remains a challenge to achieve high permittivity, low dielectric loss, and high flexibility in the single layer nanocomposites, simultaneously. In this work, a series of ternary tri-layered structure films is presented via a facile solution-casting process. Two outer layers of poly(vinylidene fluoride-co-hexafluoropropene) (P(VDF-HFP)) ferroelectric copolymer matrix are filled with acid-treated multi-walled carbon nanotubes (MWCNT) to enhance permittivity, while the inter layer of P(VDF-HFP) blended with poly(methyl methacrylate) (PMMA) can effectively suppress the dielectric losses. The acid-treated MWCNT filler, organic-organic blend, and tri-layered structure contribute to the increase of permittivity, decrease of dielectric loss, and favorable mechanical reliability. As a result, the maximized permittivity of 21 and low dielectric loss of 0.05 have been endowed in the tri-layered composites with an optimized MWCNT content of 9 wt.% at a test frequency of 1kHz. Specifically, excellent capacitive stability is demonstrated in this trilayered film over straight bending cycles (i.e. 20,000 cycles) and winding (i.e. 120 hours) tests. These attractive features of the designed tri-layered structure composites manifest that the facile approach proposed herein is scalable that can be extended to develop flexible composites with high permittivity and low dielectric loss for dielectric applications.