Synthesis of borosilazane as UV-curable borazine-type single source precursor for SiBCN ceramic materials

Two UV-curable single source precursors of borazine derivatives [B{CH2(SiR3)}NH]3 (a-TSMB) and [B{CH(CH3)(SiR3)}NH]3 (a-TSEB) (R=acrylate group) were synthesised from chloromethyltrichlorosilane and trichlorovinylsilane as starting materials, respectively. a-TSMB and a-TSEB were characterised via Fourier transform infrared, 1H NMR, 11B NMR and 29Si NMR spectroscopy. B and N existed in the form of a six-membered borazine ring, and the UV-curable acrylate groups were successfully introduced in both a-TSMB and a-TSEB. a-TSMB incorporated three UV-curable acrylate groups, whereas a-TSEB incorporated five or six acrylate groups. a-TSEB was used as a model to study these novel single source precursors with a borazine ring and acrylate function group because a-TSEB incorporated more UV-curable groups and its synthesis route was more accessible. The UV-activated polymerisation process of a-TSEB was studied via photo-differential scanning calorimetry. The results indicated that a-TSEB showed a near 84% conversion under UV radiation within 1 min, and it has excellent photoreactivity and could be UV-cured rapidly. The results of scanning electron microscopy and powder X-ray diffraction showed that an amorphous Si/B/N/C ceramic was produced by subjecting the pre-ceramic derived from a-TSEB to pyrolysis below 1400 °C.