2, Institute for Functional Imaging of Materials, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
3, Kimberly-Clark Corporation, Irving, Texas, United States
Recently, bottlebrush polymers have attracted significant interest due to their potential applications in drug delivery and electronics. The tunability of their properties, stemming from the diversity of sidechains and their spatial arrangement, have emphasized their industrial potential as compared to the linear macromolecules. In this context, the structural information and organization of these systems play a major role in the rational design of functional bottlebrush polymers. Specifically, direct observation of the molecular organization can reveal inter-chain interaction phenomena and explain the fundamental physical properties of these systems. Here, we report a new method to analyze bulk macromolecular chain arrangement of bottlebrush polymers based on Helium Ion Microscopy (HIM). By using the HIM we were able to quantify structural nematic-type ordering in an amorphous polymer bottlebrush system. High-resolution imaging coupled with data analytics has proven to highlight the location and distribution of the polymer backbones, after oxygen plasma-generated height contrast; as well as map changes in the backbone spatial arrangement as a function of thermal annealing. Our experimental findings are corroborated by the coarse-grained molecular dynamics simulations. Overall, this approach can generate clear insights on the internal structure of amorphous materials and provides a complimentary information channel to scattering techniques and theoretical modelling.
This work was performed at the Center for Nanophase Materials Sciences, a US Department of Energy Office of Science User Facility. This research used resources of the Oak Ridge Leadership Computing Facility, which is a DOE Office of Science User Facility supported under Contract DE-AC05-00OR22725. The authors acknowledge Scott Retterer at the Center for Nanophase Materials Science at Oak Ridge National Laboratory for helpful input and discussion