Multimodal correlative microscopy for isotopically resolved sub-15 nm chemical imaging of phase-separated polymer blends

The distribution of two-phase polymer blends depends on the interactions and chemical structure of the polymer components, their compatibility with the substrate, and the processing conditions. In this study, we report a multimodal correlative workflow combining AFM, ToF-SIMS, Electron Microscopy, and high-resolution Helium Ion Microscopy–SIMS (HIM-SIMS), with the latter enabling chemically resolved imaging of phase-separated PS/PMMA thin films at sub-15nm lateral resolutions. Spin-coated blends annealed exhibit surface reorganization into micron-scale droplets on a continuous matrix, as revealed by AFM. ToF-SIMS confirms the presence of both polymers at the outermost surface but cannot resolve sub-100 nm domains. HIM-SIMS overcomes this limitation by providing simultaneous secondary-electron imaging and nanoscale chemical maps. By employing deuterated PS as an isotopic label, PS-rich domains can be unambiguously distinguished from PMMA, overcoming the inherent ambiguity arising from overlapping molecular fragments in non-deuterated polymer systems. This correlative methodology offers a powerful platform for probing surface segregation, chemical heterogeneity, and interfacial organization in ultrathin polymer films, with relevance for coatings, electronics, and soft-matter interfaces. .