One-pot synthesis of novel polyborosilazane to SiBNC fibres

A processable N-methylpolyborosilazane was synthesised by an original method by using boron trichloride (BTC), trichlorosilane (TCS) and heptamethyldisilazane (HpMDZ) as the starting materials. The reaction mainly involves the condensation between B–Cl, Si–Cl and –SiMe3 with ClSiMe3 evaporation. The steric N–CH3 in the HpMDZ plays an important role in improving the processing properties of the polymer. The obtained polymer has a relatively high softening point and can easily be melt-spun into polymer fibres and then be converted into high performances SiBNC fibres. This route is suitable for the continuous preparation of the preceramic polymer for SiBNC fibres under mild conditions.