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

Abstract 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[4 H ‐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/B 2 O 3 /SiO 2 . Their use as effective flame retardant materials is demonstrated.