Open-cage silsesquioxanes (IC-POSS, incompletely condensed polyhedral oligomeric silsesquioxane) were herein employed for construction of network polymers by utilizing the open moieties as reactive sites. The obtained polymers were soluble in organic solvents despite the high molecular weights. High thermal stability and transparency were attained thanks to the inorganic components, and the refractive indices were tuned by the organic substituents.