Heterostructures of polymer photonic crystal films

This paper describes ways to multilayer opaline films (opaline heterostructures) composed from functional opal layers of spheres with different lattice constants. At first various monodisperse colloids-both cross-linked and un-cross-linked-were prepared from methyl methacrylate, methyl alpha-chloroacrylate, and methyl alpha-bromoacrylate. These colloids can be crystallized into large, well-oriented opaline films with the help of a "drawing apparatus" by the method of crystallization in a moving meniscus. After annealing, a second opaline film can be crystallized on top of these films and so on. Electron microscopy inspection shows a sharp borderline between the sublayers and no disorder on both sides although the lattice constants in both films can be incommensurable. Transmission and reflection measurements prove the high quality of the films. The use of a combination of thermolabile and thermostable colloids opens the possibility to prepare functional opaline heterostructures.