| AVS 66th International Symposium & Exhibition | |
| Surface Science Division | Tuesday Sessions |
| Session SS-TuP |
| Session: | Surface Science Poster Session |
| Presenter: | Roger Proksch, Oxford Instruments-Asylum Research |
| Authors: | V.V. Korolkov, Oxford Instruments-Asylum Research A. Summerfield, University of Manchester, UK A. Murphy, University of Nottingham, UK D. Amabilino, University of Nottingham, UK P.H. Beton, The University of Nottingham, UK M. Kocun, Oxford Instruments-Asylum Research R. Proksch, Oxford Instruments-Asylum Research |
| Correspondent: | Click to Email |
Polymers, both synthetic and natural, are ubiquitous materials whose properties are strongly influenced by packing, conformation, and monomer composition of individual macromolecules. The ability to acquire real-space images of the microstructure of these materials with molecular-scale resolution is required to advance the understanding and control of their local ordering, a key element in the precise engineering of polymer properties. Real-space images of polymers with sub-molecular resolution could provide valuable insights into the relationship between morphology and functionality of polymers, but their acquisition is problematic due to perceived limitations in atomic force microscopy (AFM).
Here we show that individual polymer chains and sub-molecular resolution may be achieved using AFM under ambient conditions through the low-amplitude (≤ 1 nm) excitation of higher eigenmodes1 of a cantilever on a range of commercial polymers (polythiophenes (PTs), polytetrafluoroethylene (PTFE), polyethylene(PE)). We have used this new approach to characterize both single strands of polymers adsorbed on surfaces as well as bulk semi-crystalline samples with Angstrom resolution. For example, on the surface of a spin-coated PT thin film, in which the thiophene groups are perpendicular to the interface, we resolve terminal CH3-groups in a square arrangement with a lattice constant 5.5A from which we can identify abrupt boundaries and also regions with more slowly varying disorder, which allow comparison with proposed models of PT domains. At the same time, bimodal tapping or AM-FM imaging2 enables modulus mapping on a wide range of polymer materials. Furthermore, molecular-level spatial resolution was achieved with AM-FM imaging on polymer chains in ambient conditions and revealed chain spacing and conformation predicted by theory and other experimental methods.
Our results highlight the important role for high-resolution AFM in determining the properties of polymer strands and thin films of technological relevance, and we anticipate future progress in correlating device performance with structural properties at the sub-molecular scale based on this technique.
1Korolkov et al., Nat. Comm., 2019
2Kocun et al., ACS Nano, 2017