Flexible h-BN/fluorinated poly (arylene ether nitrile) fibrous composite film with low dielectric constant and high thermal conductivity fabricated via coaxial electrospinning hot-pressing technique

The rapid development of electronics puts forward higher requirements on the low dielectric materials. Especially, the polymer-based dielectric film with low dielectric constant, high thermal conductivity, and heatresistance is essential to the flexible electronics. However, the balance of these intended performance is still a big challenge. In this work, we reported the flexible poly (arylene ether nitrile) (PEN) fibrous composite film with low dielectric constant and high thermal conductivity by coaxial electrospinning hot-pressing technique. Interestingly, such bi-functional fibrous composite film was rationally designed by using hexagonal boron nitride (hBN)/fluorinated PEN (PEN-F) as shell layer and polyvinylpyrrolidone (PVP) as the core layer of fibers, which could further form the porous, hollow, and balsam pear-shaped structure after the hot-pressing and dissolution process. Owing to introduction of the h-BN nanosheets, intrinsic fluorine groups of PEN-F, and hollow nanofiber structure, the dielectric constant and dielectric loss of fibrous composite film could be as low as 1.74 and 0.0092 at 1 kHz, respectively. Furthermore, the in-plane thermal conductivity of fibrous composite film could reach 0.811 W m-1 K- 1 by incorporation of 7 wt% h-BN. In addition, the fibrous composite film exhibited high thermal stability (T5 % = 498 degrees C and Tg = 182 degrees C) and mechanical strength (Tensile strength = 39.2 MPa and tensile modulus = 250.9 MPa). Therefore, this work opens up an alternative method to prepare high-performance