Soluble\nand Meltable Hyperbranched Polyborosilazanes toward High-Temperature\nStable SiBCN Ceramics

Abstract

High-temperature\nstable siliconborocarbonitride (SiBCN) ceramics\nproduced from single-source preceramic polymers have received increased\nattention in the last two decades. In this contribution, soluble and\nmeltable polyborosilazanes with hyperbranched topology (hb-PBSZ) were\nsynthesized via a convenient solvent-free, catalyst-free and one-pot\nA₂ + B₆ strategy, an aminolysis reaction of\nthe A₂ monomer of dichloromethylsilane and the B₆ monomer of tris­(dichloromethylsilylethyl)­borane in the presence\nof hexamethyldisilazane. The amine transition reaction between the\nintermediates of dichlorotetramethyldisilazane and tri­(trimethylsilylmethylchlorosilylethyl)­borane\nled to the formation of dendritic units of aminedialkylborons rather\nthan trialkylborons. The cross-linked hb-PBSZ precursors exhibited\na ceramic yield higher 80%. The resultant SiBCN ceramics with a boron\natomic composition of 6.0–8.5% and a representative formula\nof Si₁B_0.19C_1.21N_0.39O_0.08 showed high-temperature stability and retained their amorphous\nstructure up to 1600 °C. These hyperbranched polyborosilazanes\nwith soluble and meltable characteristics provide a new perspective\nfor the design of preceramic polymers possessing advantages for high-temperature\nstable polymer-derived ceramics with complex structures/shapes.