Modulating Sulfur Composition toward Ultralow Dielectric Loss Polymers: A Miscible Blending Strategy with Poly(phenylene oxide)/Poly(phenylene sulfide) Alternating Copolymers

In recent high-speed communications (i.e., 5G and 6G), insulating polymers exhibiting both a minimized dielectric constant (Dk) and dissipation factor (Df) have been extensively used to reduce dielectric loss, although the empirical Dk–Df trade-off relationship has prevented further reductions in these values. Here, we describe a rational approach for the simultaneous reduction of both Dk and Df through simple polymer blending, wherein a low-Dk ether polymer is hybridized with a low-Df sulfide polymer. Specifically, upon mixing poly(2,6-dimethyl-1,4-phenylene sulfide) (PMPS) or poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) with their alternating copolymer, differential scanning calorimetry (DSC) thermograms of the resulting polymer blends revealed their miscibility, as verified by shifting of glass-transition temperatures, allowing for the successful film preparation and the tuning of their dielectric properties without compromising other material properties (e.g., thermostability). In particular, the observed enhancement in free fractional volume for the polymer blends suggests a reduction in Dk, finally minimizing dielectric loss (Dk = 2.43, Df = 0.00081 at 10 GHz). Specifically, those dielectric losses are significantly lower than the empirical limits defined for single-component polymers. Overall, this study describes a rational strategy for the preparation of diverse insulating polymers with extremely low dielectric losses.