Resolving Multiscale (Dis)order in Conjugated Polymer Aggregates

X-ray scattering is widely employed to characterize diverse morphologies in organic semiconducting polymers with varying levels of crystallinity. These materials are often synthesized as thin films and characterized via grazing incidence wide-angle X-ray scattering (GIWAXS). However, the molecular packing motifs for most high-performance semiconducting polymers remain unknown because conjugated polymer thin films exhibit relatively few scattering peaks due to significant paracrystalline disorder. In this study, we demonstrate a new forward scattering simulation strategy to match experimental GIWAXS with simulated scattering from molecular dynamics outputs. Using this powerful forward simulation method, we match experimental data to a simulated structure quantifying both orientational and paracrystalline disorder. In films of PBDB-T-2F and P(NDI2OD-T2), commonly referred to as PM6 and N2200, respectively, we demonstrate the utility of this method in resolving previously unknown packing motifs. Importantly, we show that specific types of slip disorder produce distinct signatures in the experimental GIWAXS scattering profile, and we develop new analytical strategy for identifying slip disorder from polymer film GIWAXS. In addition to the internal structure, we use forward simulation to identify contributions in the small-angle X-ray scattering (SAXS) from aggregate size and shape within PBDB-T-2F solutions. Through computationally generated structures, we identify scattering features from semi-flexible fibril structures arising from large, well-ordered polymer fibrils in solution, suggesting that pre-aggregation significantly influences the final film morphology. These results are confirmed through cryogenic electron microscopy of a vitrified solution showing real-space images of isolated PBDB-T-2F aggregates. Our results establish a new framework for understanding the multiscale morphology of conjugated polymer films and solutions, offering avenues for optimizing organic electronic materials through solvent engineering and molecular design.