B2O3/SiO2/Phenolic Resin Hybrid Materials Produced by Simultaneous Twin Polymerization of Spiromonomers

A synthetic procedure for boron oxide/silica/carbon polymer hybrid materials is presented, which does not need water as a reagent. For this purpose, the combined polymerization of the two twin monomers 2,2′‐spirobi[4H‐1,3,2‐benzodioxasiline] 1 and spiroboronate tetra‐n‐butylammonium bis(ortho‐hydroxymethylphenolato)borate 2 is successful to produce homogeneous hybrid materials by thermal treatment in the melt at 180 °C. The achieved hybrid material shows a ternary composition. It consists of silica, polyborate‐tetra(n‐butyl)ammonium, and phenolic resin. The tetra(n‐butyl)ammonium cation within the hybrid material, originating from monomer 2, can be easily sacrificed by Hofmann degradation at 300 °C. Thereby, it serves as the proton source for the BOH moiety. This thermal treatment finally results in the formation of the boron oxide network. The reaction between both inorganic networks under the formation of SiOB bonds occurs at 450 °C in air atmosphere, which is proven with infrared spectroscopy. Oxidation and carbonization of the hybrid materials provide composite materials with a similar composition of C/B2O3/SiO2. Their use as effective flame retardant materials is demonstrated. A ternary organic–inorganic hybrid material consisting of silica, polyborate‐tetra(n‐butyl)ammonium, and phenolic resin is prepared via simultaneous twin polymerization of the two twin monomers 2,2′‐spirobi[4H‐1,3,2‐benzodioxasiline] and spiroboronate tetra‐n‐butylammonium bis(ortho‐hydroxymethylphenolato)borate. The tetra(n‐butyl)ammonium cation within the material can be sacrificed by Hofmann degradation at 300 °C to produce a boron oxide/silica/carbon polymer hybrid material.