Advanced Materials 12, (16), 1176 (2000)

Publisher: Wiley, 2000.

Recently colloidal assembly has been used to make 3D photonic crystals from a variety of materials. A typical approach is to induce sub-micron silica spheres to organize on an fcc lattice. This template, which is periodic on an optical length scale, then serves as a three-dimensional scaffolding into which another material may be infiltrated. Subsequent removal of the template by selective etching then yields a 3D photonic crystal, also called an inverted opal. In general, these structures are interesting since they have been predicted to exhibit an omnidirectional photonic band gap and enhanced optical nonlinearities. Here we show how to use colloidal self-organization to prepare photonic crystals made from a conjugated polymer, PPV. Previous attempts to fully infiltrate such templates with high molecular-weight polymers were unsuccessful, due to the large size of the molecules, which would block the pores of the opal. In contrast, we have introduced the PPV into the pores as a low molecular-weight sulphonium salt monomer. Polymerization is then induced by an in-situ base-catalyzed reaction, followed by heat treatment. The opal template may then be removed by selective etching, yielding a luminescent polymer that is three-dimensionally patterned on an optical length scale. Such active photonic crystals hold promise for exhibiting a variety of novel optical effects, such as lasing and enhanced third-order nonlinearities.