UV-Curable Polyborosilazane Precursors for SiBCN Coatings under Harsh Environments

UV irradiation is a well-established and effective process for polymer curing. However, it has been largely ignored in the field of polymer-derived ceramics (PDCs) due to its intricate mechanism and strict requirements for the precursor molecular structure. The current work designs and synthesizes a series of UV-curable polyborosilazanes containing various vinyl groups, simultaneously examines the effect of UV curing, and investigates the mechanism of curing. Cyclization mechanisms involving vinyl-free radicals and silyl-free radicals are postulated based on the molecular structure of the precursor before and after curing. The ceramic yield of UV-cured precursors is increased by up to 9.0 wt %. Moreover, SiBCN ceramics, pyrolyzed from UV-cured precursors, exhibit excellent thermal stability and remain amorphous at temperatures of up to 1600 °C. The mechanistic interpretation of UV curing opens horizons for the design and application of UV-curable ceramic precursors.