Three-dimensional imaging of sulfur chemical states in polymers with micrometer thickness using sulfur K-edge ptychographic tomography

Three-dimensional visualization of chemical bonding states in light-element materials remains challenging, particularly for micrometer-thick specimens, due to strong X-ray absorption and limited photon flux in the tender X-ray regime. Here three-dimensional chemical-state imaging of sulfur in sulfurized poly(n-butyl methacrylate) (SPBMA) samples up to ~ 3.3 µm thick is demonstrated using ptychographic X-ray computed tomography at the sulfur K-edge. A high-resolution ptychographic CT system at the NanoTerasu BL10U beamline enables quantitative mapping of electron density, sulfur concentration, and spectral metrics derived from multi-energy imaging, that serve as proxies for sulfur-sulfur and sulfur-carbon bonding states, with ~ 80 nm spatial resolution. Multi-energy volumetric analysis using four carefully chosen photon energies reveals pronounced spatial heterogeneity in sulfur bonding, distinguishing sulfur-sulfur and sulfur-carbon bonds that are inaccessible from spatially averaged spectra. This study establishes sulfur K-edge ptychographic tomography as a potential platform for three-dimensional chemical-state imaging of light-element materials, enabling new nanoscale investigations of functional polymers and energy-related materials.