Photonic Crystals of Oblate Spheroids by Blown Film Extrusion of Prefabricated Colloidal Crystals
Ding, Tao × Liu, Zhan-Fang Song, Kai Clays, Koen Tung, Chen-Ho #
Amer chemical soc
Langmuir vol:25 issue:17 pages:10218-10222
Three-dimensional photonic crystals (or photonic band gap materials) have been fabricated With oblate spheroids as the photonic building block. The nonspherical shape was realized by the blown film extrusion process of a prefabricated colloidal photonic crystal of spherical polystyrene particles. With its voids infiltrated by polyvinyl alcohol. The extrusion wits applied on the composite film at a temperature above the glass transition temperature of both polymers. The uniformly applied two-dimensional stretching retains the positional order in the prefabricated colloidal crystal; transforms the spheres into oblate spheroids; and results in orientational order between the spheroids. The morphology of the particles can be predictably changed from a sphere into an oblate spheroid with a specified aspect ratio by the extent of the blown film extrusion. Therefore, the concomitant photonic band gap properties can be tuned in a convenient way.