Self-assembled benzoxazine-bridged polysilsesquioxanes exhibiting ultralow-dielectric constants and yellow-light photoluminescent emission

A benzoxazine-bridged bis(triethoxysilane) compound (Bz-BES) has been prepared using bisphenol-A, paraformaldehyde, and 3-aminopropyltriethoxysilane as precursors. Characterization of Bz-BES has been conducted with Fourier transform infrared, nuclear magnetic resonance, molecular mass, and elemental analysis. Thermally cured polybenzoxazine-bridged polysilsesquioxane (PBz-BPSSQ) was obtained via the sol-gel and thermal treatment process of Bz-BES. PBz-BPSSQ shows a layer-by-layer lamellar structure composed of polybenzoxazine-rich and polysilsesquioxane-rich layers in the thickness of about 80-100 nm, resulting in its ultra-low dielectric constant of about 1.57 at 1 MHz. PBz-BPSSQ also displays a high glass transition temperature of about 295 degrees C and a Young's modulus of about 3.1 GPa, both are attributed to its highly cross-linked structure. Moreover, PBz-BPSSQ exhibits yellow-light photoluminescent emission at about 540 nm under excitation at 365 nm.