Since the first commercial production of silazanes in the 1980s, prices have fallen remarkably. Meanwhile, these precursors are commercially available on a ton scale at a reasonable price from Merck KGaA (Germany), but the variety of different silazanes is strongly limited, which prevents further distribution as for many applications a tailored precursor is required. However, the most common silazanes (Durazane 2250, Durazane 1800 and 1033) are liquids but possess reactive groups like Si-H, Si-vinyl, N-H, and Si-N bonds suitable for precursor modifications.This presentation gives an insight in our activities to tailor the commercial oligosilazanes for special polymer and ceramic applications. The use of tetra-n-butylammoniumfluoride (TBAF) as catalyst leads to selective cross-linking via N-H and Si-H groups resulting in a meltable polysilazane suitable for processing of ceramic SiCN fibers. Using the same catalyst, the reaction of the oligosilazanes with trifluoroethanol leads to F-modified polysilazanes for coating applications. Furthermore, a carbon rich C/Si3N4 fiber with extraordinary oxidation stability was developed using an acrylonitrile/oligosilazane hybrid polymer. Finally, the reaction of various metal-aminopyridinato complexes with silazanes led after pyrolysis to catalytically active M@SiCN ceramics for different applications.These examples demonstrate that based on only a few basic silazanes many applications can be realized, due to a smart chemical tailoring of the precursors.

Chemical tailoring of commercial oligosilazane precursors for various applications

ACS Spring Meeting 2021

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