Vinyl-methyl oligosiloxane resin was synthesized by a hydrolytic sol-gel reaction of vinyltriethoxysilane and dimethyldiethoxysilane. Hydrochloric acid was added as a catalyst to promote the hydrolysis of silane monomers to form a highly condensed siloxane resin (Condensation degree = 95 %). The vinyl-methyl oligosiloxane and hydrogen-methyl oligosiloxane resin was then cured by a thermal hydrosilylation reaction with a minimal platinum catalyst content (3 ppm). The increased cross-linking density improved the thermal decomposition temperature and lowered the weight loss at a high temperature. The fabricated methyl-siloxane hybrid material (hybrimer) shows superior thermal stability (decomposition temperature >530 A degrees C), good long-term thermal resistance (300 A degrees C, 20 h) and transparency (92 % at 450 nm, 83 % at 350 nm) in the visible and ultraviolet ranges. Based on these characteristics, the methyl-siloxane hybrimer can be applied to various applications, including thermally stable optical materials. [GRAPHICS] .