Flexible, transparent, strong and high dielectric constant composite film based on polyionic liquid coated silver nanowire hybrid

Abstract High dielectric constant films with excellent flexibility, transparency and high strength are key materials for flexible electronic devices. Herein, a novel kind of functional hybrid (AgNW@PIL) was synthesized by forming a layer of polyionic liquid (PIL) on surfaces of silver nanowires (AgNWs), which was then added into poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) to develop a series of unique high dielectric constant films (AgNW@PIL/PVDF-HFP). Comprehensive performances of AgNW@PIL/PVDF-HFP films were studied and compared with those of AgNW/PVDF-HFP films and related composite films in literature. With the increase of AgNW@PIL content, the dielectric constant and mechanical strength significantly improve, while the light transmittance gradually decreases. At the same filler content and frequency, AgNW@PIL/PVDF-HFP has higher dielectric constant, lower dielectric loss, higher light transmittance and better mechanical properties than AgNW/PVDF-HFP. The mechanism behind these attractive results is contributed to different microstructures between AgNW/PVDF-HFP and AgNW@PIL/PVDF-HFP. Specifically, different from AgNW, AgNW@PIL has good dispersibility in PVDF-HFP, and form more micro-capacitor structure and good interface polarization effect; besides, PIL coating plays a significant role in suppressing the dielectric loss of composite films. AgNW@PIL/PVDF-HFP with only 0.4 wt% AgNW@PIL simultaneously has high tensile modulus (1152.2 MPa), high tensile strength (30.9 MPa) and large elongation at break (181.0%).