Direct visualization of bottlebrush polymers in the solid state with super-resolution microscopy

Although the behavior of single chains informs our understanding of polymer physics, a clear image of single chains that depicts their behavior within a bulk, solid state has eluded the polymers community for decades. We use super-resolution optical microscopy to capture clear and convincing images of individual chains within a bulk material using a model system of densely grafted chains called bottlebrush polymers. In this work, we directly visualize individual bottlebrush polymers by mixing dilute quantities of fluorescently-labeled bottlebrush chains with unlabeled linear polymers in films prepared by spin coating. We use these images to directly study chain conformation and orientation. We have found chains in this system are more rigid that previously reported in dilute solutions, and we explain these discrepancies by examining backbone conformation and its dependence on side chain length, grafting density, and molecular weight of the surrounding matrix. We have also found that chains orient in the direction parallel to centripetal force during spin coating. We investigate this phenomenon further by studying the dependence of chain orientation on location relative to center of the sample, solvent used for spin coating, and spin speed.