Tailoring electronic delocalization via fluorinated hyperbranched polysiloxane for colorless, transparent, and degradable cyanate ester resin

Exceptional dielectric properties position cyanate ester (CE) resins as premier candidates for co-packaged optics. However, low transparency and high cost critically hinder their application, challenges entirely overlooked in prior research. Herein, we propose a pioneering strategy to achieve colorless, transparent, and degradable CE resins through modulating electron delocalization via fluorinated hyperbranched polysiloxane (FHPSi). Trifluoromethyl groups in FHPSi exert a strong electron-withdrawing inductive effect, disrupting the adjacent phenyl-oxygen energy-level matching to suppress oxygen lone-pair electron delocalization. Consequently, restricted electron delocalization not only minimizes visible-light absorption, yielding the colorless material with 100% transmittance, but also triggers high-energy oxygen states to facilitate siloxane cleavage, enabling complete material degradation in acidic tetrahydrofuran within three days without grinding. Notably, the resulting material also exhibits an ultralow dielectric loss of 0.0031 at 10 GHz (90.0% lower than pure CE), alongside concurrent enhancement in strength and toughness. This work establishes a new paradigm for advanced CE-based electronic packaging materials.