Ultrahigh Electromagnetic Wave Transmitting Polyphenylene Sulfide Microcellular Foams Based on Molecular Structure Design for 5G Communication

Abstract

In the scenario of fifth-generation communication, especially millimeter wave (mmW) transmission, microelectronic material is required to have better signal stability, that is, a lower dielectric constant (Dk) and dielectric loss (Df). This work takes full advantage of the low dielectric molecular structure characteristics in polyphenylene sulfide (PPS) and the nonresidual low dielectric characteristics of supercritical CO2 (scCO2) foaming to enhance the low dielectric performance. The distinct structure of a highly stable thioether bond and highly reactive hydrogen in the benzene ring in the PPS macromolecule enables the oxo-bridging between PPS molecular chains and hence increases PPS melt strength. By further adjusting the regularity in PPS molecular chains to broaden the melting range of PPS crystals, the PPS microcellular foam of large expansion ratio (16.5-fold) with uniform cells is obtained. It has an ultralow Dk of 1.14 and Df of 0.0005 at 3 GHz. In the Ka band of 26–40 GHz, the broadband signal transmission has nearly no loss (∼99%). Furthermore, it has a low density (<0.08 g/cm3), is hydrophobic (contact angle of 123.4°), and reaches V-0 level flame retardancy. This ultrahigh mmW transmission material with excellent comprehensive performance provides an alternative for solving the problems of mmW propagation in the existing dielectric materials.