Site-specific molecular design of low-dielectric benzocyclobutene (BCB)-sub-nanometer inorganic nanocomposites

Abstract A facile synthetic strategy for generating polymer-inorganic nanocomposites with highly dispersed nanodomains, such as silsesquioxane, covalently bonded within a benzocyclobutene (BCB)-functionalized polycarbosiloxane matrix is reported. This approach leverages click coupling and thermally induced cycloaddition reactions to embed oligomeric silsesquioxane, achieving a unique molecular structure with promising low-dielectric applications. The synthesis involves a platinum-catalyzed hydrosilylation to prepare the silsesquioxane component, followed by hydrolytic polycondensation and thiol-ene click reactions that integrate polyhedral oligomeric silsesquioxane ladder/cage-like or network structures into the polymer matrix. A subsequent Diels-Alder reaction with BCB ensures a fully cured material. The distinct molecular structure bestows the materials with an ultra-low dielectric constant (Dk) of 1.78 and a dissipation factor (Df) of 2.73×10-3 at 1.15 kHz, positioning these values among the top reported for low-dielectric (low-k) materials. This discovery introduces a pioneering design paradigm for polymer-inorganic nanocomposites with well-dispersed sub-nanometer inorganic structure, paving the way for the future investigation of BCB−inorganic nanocomposites with ultra-low Dk.