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.

This paper presents the synthesis and characterization of (TMS-ethynyl)-substituted germa [4]pericyclyne composed of acetylene moieties and germanium atoms. Characterization was performed by X-ray crystallography, UVvis absorption, and photoluminescence spectroscopy. DFT calculations suggested interactions between the side chain alkynes and the ringforming acetylenes through germanium vertex atoms. Keywords: Element-blocks | Germanium | PericyclynesResearch on polyacetylene materials has attracted increasing attention with the growing importance of "element-blocks" (functional nano building blocks composed of heteroatoms) for advanced electronic and optical materials.1,2 Skipped polyynes ([R 2 XC¸C] n ) have received particular interest as a versatile "element-block" due to their easy modification and tunability of their characteristics by choosing appropriate linker atoms (X). Specifically, recent reports reveal that by using group 14 heteroatoms like silicon, with smaller ionization energies than those of carbon, one can achieve electron delocalization (although usually, the conjugation is interrupted at the alkyne units), resulting in effective enhancement of electric and optical properties.4 Therefore, skipped polyynes are potential candidates for preparing functional materials such as semiconductors, ceramic precursors, and hole-transporting materials. 5We have studied the synthesis and properties of both acyclic and cyclic germylene-ethynylene materials containing germanium (Scheme 1).6 Having a smaller ionization energy than silicon, germanium also forms stronger bonds to sp-carbon compared to tin. Additionally, cyclic skipped Ge-polyynes, called germa [N]pericyclynes, display characteristic emission properties compared to acyclic molecules, due to the fixed conformations and through-bond/through-space interactions. Therefore, element-block polymers composed of germapericyclynes, which are expected to impart functionality superior to that provided by monomeric pericyclyne units, are a promising platform for the fabrication of unique optical materials. Polymeric pericyclyne materials with linear, branched, dendric, and spirocyclic forms can be designed, with each pericyclyne unit connected via alkyne bridges. Thus, to enable electronic delocalization across the alkyne units, it is necessary for the vertex atoms to mediate conjugation between the alkyne spacers. The existence of alkynealkyne interactions through Ge atoms in pericyclyne ring systems has been suggested in our previous investigations.6 Thus, exo-ethynylated pericyclynes could be expected to show exoendo and exoexo alkynes interactions, and would be suitable candidate monomer units for polypericyclynes. However, their optical properties along with their molecular orbitals have not been studied yet. To explore the unique character of germa[N]pericyclynes as polymer precursors, we herein disclose the synthesis of an ethynylated germa[4]pericyclyne for preliminary research on poly(germapericyclynes), and provide a discussion of its properties.Star...

We herein describe the syntheses and characterization of extended germa[N]pericyclynes, which are macrocycles composed of germanium-butadiyne units. The obtained novel extended germa[4]-[8]pericyclynes were characterized by X-ray crystallography, UV-Vis spectroscopy, fluorescence and phosphorescence emission spectroscopy, and cyclic voltammetry, and exhibited characteristic absorptions and emissions. Density functional theory (DFT) calculations suggested smaller HOMO-LUMO gap energy compared to that of general germapericyclynes.

Synthesis and optical properties of skipped polyynes comprising germanium-acetylene units are presented. The prepared germanium polymers were investigated by UV-vis, fluorescence, and phosphorescence spectroscopy and DFT calculations. The optical properties were compared to those of cyclic compounds, germa [N]pericyclynes. The unique fluorescence and phosphorescence behaviours of acyclic polymers were observed.