Transition from transparent aerogels to hierarchically porous monoliths in polymethylsilsesquioxane sol-gel system

► Monolithic porous polymethylsilsesquioxane gels are prepared by sol-gel. ► Macropores and mesopores are controlled by an addition of nonionic surfactant. ► Transparent aerogels are formed with high concentration of surfactant. ► Hierarchically porous gels are formed with low concentration of surfactant.