Direct Observation of the Relationship between Molecular Topology and Bulk Morphology for a π‑Conjugated Material

High-performance organic semiconducting materials are reliant upon subtle changes in structure across different length scales. These morphological features control relevant physical properties and ultimately device performance. By combining in situ NMR spectroscopy and theoretical calculations, the conjugated small molecule TT is shown to exhibit distinct temperature-dependent local structural features that are related to macroscopic properties. Specifically, lamellar and melt states are shown to exhibit different molecular topologies associated with planar and twisted conformations of TT, respectively. This topological transformation offers a novel avenue for molecular design and control of solid-state organization.