Novel block Co-polymers as potential photonic materials.

Abstract

Photonic crystals, which are a specific type of photonic material, consist of regular, periodic structures composed of alternating high and low refractive index materials. They may exist inl-D, 2-D or 3-D forms, which are analogous to the morphologies adopted by self-assembling block-copolymers. Three series of well-defined block co-polymers in which the blocks had high-contrast refractive indices, were synthesised. The first series consisted of styrene-fluoromethacrylate block co-polymers, which were synthesised by living anionic polymerisation (LAP) of styrene and a fluoromethacrylate. Molecular weights, block molar ratios and fluoromethacrylate monomers were varied. The second series consisted of ք-bromostyrene-methacrylate block co-polymers, which were synthesised by the direct bromination of the styrene block of LAP- prepared styrene-methacrylate block co-polymers. Molecular weights and block molar ratios were varied.The third series consisted of ք -bromostyrene-fluoromethacrylate block co-polymers, which were synthesised by the direct bromination of the styrene block of LAP- prepared styrene-fluoromethacrylate block co-polymers. Molecular weights and block molar ratios were varied. All series were analysed by Size Exclusion Chromatography, proton Nuclear Magnetic Resonance spectroscopy (NMR) and, where appropriate, (^13)carbon NMR and (^19)fluorine NMR. The brominated co-polymers underwent Elemental Analysis. Refractive indices of the constituent homopolymers of both series, and where possible, the co-polymers, were determined. Evidence for the self-assembly of one particular styrene-fluoromethacrylate block co-polymer into a 1-D (lamellar) structure was achieved using Small Angle X-Ray Scattering.