Well-Ordered Nanostructure SiC Ceramic Derived from Self-Assembly of Polycarbosilane-Block-Poly(methyl methacrylate) Diblock Copolymer

Abstract

The fabrication of SiC ceramic materials with an ordered nanostructure through the direct pyrolysis of a self-assembled inorganic-organic block copolymer has generally been unsuccessful even though the versatile processibility has been demonstrated with organic-organic block copolymers. Here we report the synthesis of a novel polycarbosilane-block-poly(methyl methacrylate) diblock copolymer through ring-opening living anionic polymerization in a THF and n-hexane solvent system at -48 degrees C. The resulting block copolymer exhibited phase-separation behavior on the nanoscale to form a self-assembled nanostructure that was converted to a mesoporous ceramic after heating at 800 degrees C. The characterization of diblock copolymer is simultaneously investigated by GPC, and NMR analyses. The self-assembly of diblock copolymer is characterized by small-angle X-ray scattering (SAXS), atomic force microscopy (AFM), and scanning electron microscopy (SEM). In particular, the preparation of high-temperature-stable nanostructured silicon carbide and mesoporous silicon carbide ceramic directed from cross-linked polycarbosilane blocks with a high ceramic yield are described, which exhibits well-oriented nanostructures with the size in a range of 4-10 nm. These exciting results have a great potential to open a new field for the generation of nanostructured non-oxide ceramic or metal-ceramic materials for a broad class of applications.