Development of low dielectric loss poly(phenylene ether sulfone) by incorporation of 4-cyclohexylphenoxy side groups

Reducing dielectric losses in insulating materials is crucial for the development of next-generation high-frequency communication systems operating in GHz and THz ranges. This study successfully reduced dielectric constant (D_k) and dielectric loss tangent (D_f) of poly (phenylene ether sulfone) (PPES) by incorporating a newly synthesized bisphenol monomer bearing 4-cyclohexylphenoxy groups. Compared to a standard PPES without side chains (D_k = 2.92, D_f = 0.0167 at 10 GHz), the polymer modified with 4-cyclohexylphenoxy groups exhibited a reduced dielectric constant (D_k = 2.69) and dielectric loss tangent (D_f = 0.0043) at the same frequency. Wide-angle X-ray diffraction (WAXD) analysis suggested the formation of a higher-order structure due to the introduction of bulky substituents. Moreover, the modified polymer exhibited thermal stability exceeding 400 °C. In addition, the introduction of this side chain improved the hydrophobicity of the surface. These results indicate that selective incorporation of appropriate side chains effectively reduces dielectric losses, providing insights for developing advanced insulating materials suitable for high-frequency applications.