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

Abstract

Mesoporous nonoxide ceramics are attractive for applications such as catalytic supporters and separations with exceptional thermochemical stability. Here we report on the one-step 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 m2 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.

Polymerization Induced Microphase Separation for the Fabrication of Nanostructured Materials

“… Chemical processing techniques compatible with the PIMS process. a) Thermal curing to form macro‐scale monoliths (photographs, bottom left) [10,53] and micro‐scale PIMS needles (SEM image, bottom right) thermally produced from a microfabricated mold [13] (scale bar=200 μm for SEM image, bottom right); b) PIMS in microfluidic processing utilizing a double emulsion to create microcapsules [12a] (scale bar=100 μm for SEM image, bottom left); c) light mediated 3D printing; [54] d) thin films via photopolymerization [45] (as shown) or thermal polymerization; [12b,44] e) tunable microspheres via PIMS in suspension polymerization (scale bars=200 μm); [16b] f) PIMS within high internal phase emulsions to form hierarchically macro‐ meso‐ and micro‐ porous materials [51] …”

Customized Nanostructured Ceramics via Microphase Separation 3D Printing

“…Conventional synthetic approaches for controlled fabrication of nanostructured preceramics rely on i) soft/hard templating, [ 4 ] ii) self‐assembly of organic–inorganic block copolymers [ 5 ] or co‐assembly of inorganic precursors with organic block copolymers, [ 6 ] or iii) organic–inorganic hybrid polymerization‐induced microphase separation (PIMS). [ 7 ] In the first approach, a preceramic precursor co‐assembles with soft organic materials or is filled into a preordered hard template followed by ceramization and selective template removal. The second and third approaches involve the generation of microphase separated structures of silicon‐containing block copolymers or inorganic precursors with organic block copolymers, which are then pyrolyzed to convert them into nanostructured ceramics.…”

Synthesis of tubular silica fiber via all‐aqueous microfluidics for geopolymer regulation

“…Thus, the preceramic template can be prepared with fine controllability and flexibility. The commonly used methods to synthesize preceramic templates include sol–gel, 14–17 gel casting, 18,19 replica, 20–22 3D printing, 23–26 microfluidics, 27,28 and so forth. Liang et al 29 .…”

“…Thus, the preceramic template can be prepared with fine controllability and flexibility. The commonly used methods to synthesize preceramic templates include sol-gel, [14][15][16][17] gel casting, 18,19 replica, [20][21][22] 3D printing, [23][24][25][26] microfluidics, 27,28 and so forth. Liang et al 29 introduced a phase reunion assisted sol-gel method to prepare hollow ZrO 2 microparticles, which improved the efficiency by reducing the equilibrium time needed for the sol-gel system.…”