Superhydrophobic Electrospun PI/PTFE Membranes with Ultralow Dielectric Constants for High-Frequency...

High-frequency, high-power, and high-speed telecommunication in a complex environment promotes the development of dielectric materials toward a low dielectric constant, low dielectric loss, good thermal properties, and long-term reliability. Here, polyimide/polytetrafluoroethylene (PI/PTFE) nanofiber membranes with an inherent super hydrophobicity, excellent dielectric properties, good thermal stability, and enhanced tensile strength were prepared via a simple electrospinning strategy and an imidization reaction. The obtained PI/PTFE membranes demonstrate a superlow average dielectric constant of 1.22-1.27 and a dielectric loss of 0.032-0.048 in high frequency, together with an enhanced tensile strength, benefiting from the special nanofiber-bead structure formed in the composite membrane. The mixing of polyamic acid (PAA) and PTFE in the electrospinning solution endows the obtained PI/PTFE nanofiber membrane with a uniform distribution of PTFE and thus an inherent superhydrophobicity with a water contact angle of 156.1 and 159.2° for PI/PTFE-30% and PI/PTFE-40%, respectively. Besides, the hydrophobicity could be kept even after standing more than 10,000 water drops, and the thermal properties exhibited promising results with T_max = 587 °C and T_d5% = 423 °C, rendering these PI/PTFE membranes favorable alternatives for prospective telecommunication.