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Synthesis of silicon nitride based ceramic nanoparticles by the pyrolysis of silazane block copolymer micelles



Diblock copolymer poly(1,1,3,N,N′-pentamethyl-3-vinylcyclodisilazane)-block-polystyrene (polyVSA-b-polySt) and triblock copolymer poly(1,1,3,N,N′-pentamethyl-3-vinylcyclodisilazane)-block-polystyrene-block-poly(1,1,3,N,N′-pentamethyl-3-vinylcyclodisilazane) (polyVSA-b-polySt-b-polyVSA), consisting of silazane and nonsilazane segments, were prepared by the living anionic polymerization of 1,1,3,N,N′-pentamethyl-3-vinylcyclodisilazane and styrene. PolyVSA-b-polySt formed micelles having a poly(1,1,3,N,N′-pentamethyl-3-vinylcyclodisilazane) (polyVSA) core in N,N-dimethylformamide, whereas polyVSA-b-polySt and polyVSA-b-polySt-b-polyVSA formed micelles having a polyVSA shell in n-heptane. The micelles with a polyVSA core were core-crosslinked by UV irradiation in the presence of diethoxyacetophenone as a photosensitizer, and the micelles with a polyVSA shell were shell-crosslinked by UV irradiation in the presence of diethoxyacetophenone and 1,6-hexanedithiol. These crosslinked micelles were pyrolyzed at 600 °C in N2 to give spherical ceramic particles. The pyrolysis process was examined by thermogravimetry and thermogravimetry/mass spectrometry. The morphologies of the particles were analyzed by atomic force microscopy and transmission electron microscopy. The chemical composition of the pyrolysis products was analyzed by X-ray fluorescence spectroscopy and Raman scattering spectroscopy. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4696–4707, 2006