We present here part of an ongoing study on structure−processing−property relationships in cubic silsesquioxane (cube) nanocomposites. Here, we focus on imide nanocomposites prepared from octaaminophenylsilsesquioxane (OAPS) as a model nanobuilding block for rigid, high-temperature hybrid nanocomposite materials. OAPS units are linked NH2 vertex to NH2 vertex by reaction with various dianhydrides to form three-dimensional nanocomposites. The architecture of the organic tethers between vertices can be manipulated to optimize processability, rigidity, and thermomechanical properties. Studies were initiated using an extreme tether structure with zero flexibility prepared by solvent casting and then curing mixtures of OAPS with pyromellitic dianhydride (PMDA) at 330 °C. The resulting materials are extremely brittle, making thermomechanical property measurements quite difficult. Tether rigidity, length, and cross-link densities were then modified using reactions of OAPS with oxydiphthalic anhydride (ODPA) and ...