Synthesis of Low Dielectric Poly(ester imide)s Incorporating Double-Decker Silsesquioxane Units

This study aims to synthesize poly(ester imide)s (PEIs) incorporating double-decker silsesquioxane (DDSQ) units to achieve low dielectric constants (Dks) for high-frequency applications. The incorporation of bulky DDSQ structures hindered the stacking of polymer chains, effectively reducing Dk compared to conventional PEIs. The rigid structure of DDSQ suppressed segmental motion, thereby preventing increases in the dissipation factor (Df). The synthesized DDSQ-containing PEI exhibited a Dk of 2.81 and a Df of 0.0028 at 10 GHz, and an average refractive index (nav) of 1.564, demonstrating its potential as a low-dielectric material. Furthermore, since the DDSQ-containing PEI achieved a reduction in Dk while maintaining a low Df, this study provides a valuable design strategy for further reducing the dielectric properties of PEIs.