Tailorable copolysilazanes (CPSZs) with variable chemical structure and molecular weights were prepared by coammonolysis of dichloromethylsilane, dichloromethylvinylsilane, and trichloromethylsilane. The as-synthesized CPSZ was characterized by gel permeation chromatography, Fourier transformed infrared (FTIR) spectroscopy, and nuclear magnetic resonance spectroscopy. The CPSZ could be cured in an inert atmosphere at 180 degrees C for 24 h. Pyrolysis behavior and structure evolution of the cured CPSZ were studied by means of thermal gravimetric analysis and FTIR. Hydrosilylation, transamination, dehydrogenation, and demethanation reactions were involved in the polymer-to-ceramic conversion of CPSZ. The ceramization process was complete at 900 degrees C with a ceramic yield of 81-84%. Elemental analysis indicated that the compositions of final ceramics can be tailored by controlling the feed ratios of the starting chlorosilanes. Moreover, the microstructural evolution of the resultant Si-C-N ceramics was further investigated by X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 1286-1292, 2011