Synthesis of in Situ Microphase-Separated Organic-Inorganic Block Polymer Precursors to 3D-Continuous Mesoporous SiC-based Ceramic Monoliths

Mesoporous nonoxide ceramics are attractive for applications such as catalytic supporters and separations with exceptional thermochemical stability. Here we report on the onestep preparation of microphase-separated bicontinuous organic- inorganic polymer precursors for forming 3D continuous polymer-derived ceramic monoliths without an external block copolymer template and annealing steps. We combined polymerization-induced phase separation with in situ hybrid block polymer formation from a mixture of a preceramic monomer, a cross-linker, and a thermally decomposable organic segment containing a terminal chain transfer agent. The resultant cross-linked polymeric monoliths, moldable to any desired shape, were converted to 3D-continuous mesoporous silicon carbonitride ceramics with a pore size in the 3-11 nm range and a surface area of 107-410 m(2) g(-1) by varying the molar mass of the sacrificial organic block and the pyrolytic temperature. The 3D-disordered pore structure is beneficial for retaining the monolithic shape via isotropic shrinkage during ceramization. The distinctive characteristics of this synthetic approach, which are the absence of a solvent, a structure-directing block copolymer, and an annealing process, are affordable for the large production of nanoporous ceramic monoliths for various high-temperature applications and should be applicable for additive manufacturing with direct polymerizability for the fabrication of hierarchically porous materials in complex shapes with dimensional scalability.