A compound having the formula. Each R is methyl or phenyl; R2 comprises one or more of silane, siloxane, and aromatic groups; n is a nonnegative integer; and m is 1 or 2. The dashed bond is a single bond and the double dashed bond is a double bond, or the dashed bond is a double bond and the double dashed bond is a triple bond. A polymer made by a hydrosilation reaction of a polyhedral oligomeric silsesquioxane having pendant siloxane groups with an acetylene- and silicon-containing compound having at least two vinyl or ethynyl groups, and a crosslinked polymer thereof. The reaction occurs between the pendant siloxane groups and the vinyl or ethynyl groups.