nanoporous polymers with gyroid nanochannels can be fabricated from the self - assembly of degradable block copolymer , polystyrene - b - poly , followed by the hydrolysis of plla blocks . a well - defined nanohybrid material with sio 2 gyroid nanostructure in a ps matrix can be obtained using the nanoporous ps as a template for the sol - gel reaction . after subsequent uv degradation of the ps matrix , a highly porous inorganic gyroid network remains , yielding a single - component material with an exceptionally low refractive index .