Polymer-based coatings are widely applied in modern industry and technology. While volatile organic solvents were used conventionally for the formation of polymer coatings, the world-wide environmental concerns they could bring about have been calling for replacement with water-based charge-stabilized colloidal suspension. In colloid-based coatings, during the drying process of the solvent, the colloidal particles fuse together and eventually form the coating, the mechanical and corrosion

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... ance properties of which sensitively depend on the internal morphology. However, the understanding on the pathway of the formation of a dense coating with specific morphology from individual colloids, which is critical to the final morphology, is largely missing, especially at the single-particle level. The colloidal suspension composed of polymeric colloids and multiple ionic groups can go through complex processes during sintering and coating formation. On one hand, the interplay among particle diffusion, particle interactions, interfacial tensions, and solvent evaporation introduce different categories of processes and stages in the sintering [1] [2] [3] . On the other hand, the corresponding concentrations and the environmental conditions of the components undergoing changes that can potentially make a difference in the final properties of coating [4] . Scanning electron microscopy, cryo electron microscopy, and optical microscopy have been used to study the microstructure of coatings as well as the dynamics of the colloids [5] [6] [7] , less has been done on the connection of chain interpenetration, crystallinity with particle deformation, or on how chain the ionic groups reorganize at various stages of film formation. In comparison, liquid-phase transmission electron microscope (TEM) can provide direct information of the sintering process at proper electron dose rate [8] [9] , especially the dynamics at the nanoscale such as particle deformation and fusion.