Materials combining the best properties of plastics and ceramics, i.e., that are as heat and combustion resistant as ceramics and as moldable and light as plastics, would find many applications. As a step in this direction, the preparation and properties of a silicon-based organic polymer, MSP, which includes the Si(H)-C unit, and related polymers are described. MSP's extremely high temperature of 5% weight loss (860 degrees C) indicates that further investigation of polymers containing the Si(H)-C unit could be fruitful.