Thermosets and ceramic chars were characterized for three polymeric materials consisting of diacetylene-siloxane repeat units, DaS, diacetylene-siloxane-carborane-siloxane repeat units, DaSCS, and a 90/10 copolymerization. The goal was to incorporate the known thermo-oxidative stability of the siloxane-carborane elastomers into high performance thermosets and ceramic chars. The DaSCS thermoset has excellent thermo-oxidative stability as determined by a low weight loss and tough residue after annealing 100 hours in air at 316°C, however the glass transition is a low 94°C. DaS and 90/10 thermosets do not undergo glass transitions below 350°C and have low weight losses on thermo-oxidative aging, however the residue was quite brittle. The much higher carborane content in DaSCS also seems to help in ceramic char formation. All polymers had similar char yields to 800°C, whereas DaSCS solidified to a 15% denser ceramic.