Real-space mapping of deuterated polymers using dark-field EELS

Gatan instruments used

Low voltage Gatan imaging filter (GIF) and STEMPack™

Background

Isotopic labeling using hydrogen and deuterium is widely applied in polymer and soft-matter science to probe structure and dynamics. Small-angle neutron scattering (SANS) can distinguish H and D, but provides only averaged structural information in reciprocal space. Conventional electron microscopy lacks isotope sensitivity, and bright-field vibrational electron energy loss spectroscopy (EELS) suffers from severe signal delocalization. This study addresses these limitations by applying dark-field vibrational EELS (DF-EELS) to achieve localized, isotope-sensitive spectroscopy in real space. In this work, Senga et al. demonstrate how DF-EELS in a monochromated scanning transmission electron microscope (STEM) is used to map the real-space distribution of carbon–hydrogen (C–H) and carbon– deuterium (C–D) bonds in a block copolymer of deuterated polystyrene (dPS) and poly(2-vinylpyridine) (P2VP) [1]. The approach achieves single-nanometer spatial resolution, while maintaining sufficient energy resolution to clearly distinguish isotopic vibrational modes. Unlike neutron scattering techniques, which provide ensemble-averaged information, DF-EELS enables direct visualization of local molecular-scale structures in polymers.