Resonant Tender X-ray Diffraction for Disclosing the Molecular Packing of Paracrystalline Conjugated Polymer Films

The performance of optoelectronic devices based on conjugated polymers is critically dependent upon molecular packing; however the paracrystalline nature of these materials limits the amount of information that can be extracted from conventional X-ray diffraction. In this presentation it will be shown that resonant diffraction (also known as anomalous diffraction) is able to provide new molecular packing information about conjugated polymer films. Resonant diffraction effects will be demonstrated for several common sulfur-containing polymers whereby rapid changes in diffraction intensity are observed as the X-ray energy is varied across the sulfur K-edge. These changes – combined with theoretical calculations – make it possible to discriminate between different packing geometries, which opens up a new way to unlock important microstructural information about conjugated polymer thin films for which only a handful of diffraction peaks are typically available.