Deformation Behavior\nof Microparticle-Based Polymer\nFilms Visualized by AFM Equipped with a Stretching Device

Understanding the structural changes and property alterations\nat\nthe nanoscale and microscopic levels is critical to clarifying the\ndeformation behavior and mechanical properties of polymer materials.\nEspecially, in latex films composed of polymer nanoparticles, it is\nwidely accepted that the remaining interfaces between microparticles\nin the film affect their brittleness. However, detailed information\non nanoscale changes of latex films during deformation remains unclear\ndue to technical difficulties in analyzing the microstructures under\nmechanical stress. In this study, we employed atomic force microscopy\nequipped with a uniaxial stretching device to visualize the surface\nstructures of films composed of slightly cross-linked microparticles\nunder elongation strain. The observations revealed that the latex\nfilm deforms in a nonaffine manner, which is attributed to the concurrent\ndeformation of individual microparticles and the pull-out of interpenetration\nbetween them. Furthermore, by introducing a load–strain measurement\nmechanism to the stretching device, we compared the relationships\nbetween nanostructural changes, local property changes, and macroscopic\ndeformation of microparticle-based films. The results suggest that\nloads are dominated by the deformation of microparticles and dissipate\nas the interpenetration of surface polymer chains between microparticles\nis pulled out.