Synthesis and characterization of block copolymer/ceramic precursor nanocomposites based on a polysilazane

The amphiphilic block copolymer poly(isoprene‐block‐ethylene oxide) was used as a structure‐directing agent for a polysilazane preceramic polymer commercially known as Ceraset. Two block copolymers of different molecular weights and poly(ethylene oxide) weight fractions with body‐centered cubic sphere and hexagonal cylinder morphologies were used. To both polymers, 50 wt % of the silazane oligomer (Ceraset) was added. The resulting composites were cast into films and characterized by small‐angle X‐ray scattering and transmission electron microscopy. The silazane was chemically compatible with the poly(ethylene oxide) microdomains of the block copolymer, and this resulted in a swelling of those domains. After the cooperative self‐assembly of the block copolymer and Ceraset, for both systems the structure was permanently set in the lamellar morphology by the crosslinking of the silazane oligomer with a radical initiator at 120 °C. These results suggest that the use of block copolymer mesophases may provide a simple and easily controlled pathway for the preparation of various high‐temperature SiCN‐type ceramic mesostructures.