Nanoscale C–H/C–D mapping of organic materials using electron spectroscopy

Abstract

Distinguishing hydrogen from deuterium using atomic-scale imaging and spectroscopy is crucial for identifying microscopic structures and the origins of the properties of organic materials. However, conventional structural analysis techniques for materials containing both isotopes, such as neutron scattering, provide only averaged information across the beam area. Here we utilize vibrational spectroscopy using a monochromated transmission electron microscope to discretely image hydrogen and deuterium in organic polymers at single-nanometre resolution. This technique allowed carbon–hydrogen and carbon–deuterium stretches to be mapped, which uncovered the surface segregation of the deuterated polystyrene component within a block copolymer film composed of deuterated polystyrene and poly(2-vinylpyridine). Moreover, it enabled clear visualization of the spatial distribution of hydrogenated and deuterated polystyrene on a molecular scale in a bulk block copolymer specimen containing both components. This method, integrated with coarse-grained molecular dynamics simulations, revealed a localized feature of polymer chains corresponding to the reptation tube, which could not be identified using conventional scattering techniques.