Nanoparticle-filled rubber under tensile deformation was observed in situ by transmission electron microscopy (TEM), and the spatial distributions of the local maximum and minimum principal strains (ε max and ε min ) under tensile deformation were determined experimentally for the first time. The local ε max showed that deformation behavior depends heavily on the local structures and their spatial arrangements. Additionally, greatly deformed rubbery regions were found to appear along a network consisting of silica aggregates (silica-aggregate network). The distribution of the local ε min revealed the reorganization mechanisms of the internal hierarchical structures. The finite element method (FEM) was then applied to a series of TEM images under tensile deformation to simulate the structural changes, principal strains, and von Mises stress. The simulated morphology and ε max were in excellent agreement with the experimentally obtained morphology and strain. The distribution of the simulated von Mises stress, obtainable only from the FEM based on the experimental results, revealed that large stress propagates along the silica-aggregate network parallel to the tensile direction, suggesting that the silica-aggregate network may be primarily responsible for providing mechanical strength to the nanoparticle-filled rubber under deformation. Since the stress concentrates along the silica-aggregate networks, cavities appeared along these "stress pathways." The present study would pave the way to understanding the microscopic factors determining the macroscopic mechanical properties of rubber nanocomposites mainly used for automobile tires and seismic isolation rubber.

The synthesis and characterization of novel pericyclynes comprising germanium atoms and acetylenes, germa[n]pericyclynes, are described. The prepared germa[4]-, [6]-, and [8]pericyclynes were compared by (13)C NMR spectroscopy, X-ray crystallography, cyclic voltammetry, UV-visible spectroscopy, fluorescence emission spectroscopy, Raman spectroscopy, and density functional theory calculation analyses.

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Although fracture resistance is critical for rubber materials, the fracture mechanisms are poorly understood from a microscopic perspective. In this study, a crack propagation process in rubber with silica nanoparticles, which is commonly used to enhance the mechanical properties of rubber materials, was successfully observed in situ with nanoscale resolution using transmission electron microscopy (TEM). The consecutive time-sliced TEM images clarified that the crack tip propagated along the interfaces between the rubber matrix and aggregates of silica nanoparticles (rubber-aggregate interfaces). Moreover, the path and propagation rate of the crack were significantly affected by the heterogeneous distribution of the silica aggregates, which resulted in a "stickslip" propagation behavior of the crack tip. Detailed spatial strain analysis revealed that the local maximum principal strain (ε max ) around the crack tip was nonuniform. The crack tip propagated through regions with large ε max , delaminating the rubber-aggregate interfaces. This study successfully demonstrated that the heterogeneous distribution of nanoparticles significantly affects the fracture behavior of nanoparticle-filled rubbers.