Superhydrophobic ZIF-8/PEN films with ultralow dielectric constant and outstanding mechanical properties

Polymer dielectrics with stable ultralow dielectric constant (k) and outstanding flexibility are expected to be used in the field of high-speed communications system. Herein, in order to reduce dielectric constant, enhance hydrophobic properties and increase flexibility of dielectric material, ZIF-8/polyarylene ether nitrile (PEN) films are reasonably designed and successfully fabricated via delayed phase inversion approach. It is intriguingly found that with the increase of the amount of ZIF-8, the honeycomb microporous structure, dielectric properties, water resistance and mechanical properties of ZIF-8/PEN films can be finely tuned. The results show that ZIF-8 grows uniformly on the honeycomb pore walls of ZIF-8/PEN films, and the size of honeycomb pores increases from 1.6 μm to 5.8 μm with the increase in the amount of ZIF-8. The dielectric constant of ZIF-8/PEN films is significantly reduced from 1.83 to 1.41. The ZIF-8/PEN films can maintain k values under 1.5 when exposing to a relative humidity of 80% for 7 days. More laudably, the ZIF-8/PEN films reveal superior elongation at break higher than 112% and outstanding flexibility which can be folded repeatedly without rupture. The approach of regulating the pore size by generating ZIF-8 in situ to adjust the dielectric and mechanical properties of composites opens up a novel way for the design of flexible ultra-low dielectric materials.