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Abstract Nanoparticle reinforcement is a general approach toward the strengthening of elastomer nanocomposite in large‐scale applications. Extensive studies and efforts have been contributed to demonstrating the property reinforcement of polymer nanocomposites in relation to matrix‐filler and filler‐filler interaction. Here, a facile synthetic method is creatively reported to synthesize SiO_2,15/120‐g‐polyisoprene (SiO₂‐g‐PI) particle brushes using atom transfer radical polymerization (ATRP). The dispersion and microstructures of the nanoparticles in the nanocomposites are investigated by morphological characterizations, whereas the reinforcing mechanism is studied through mechanical measurements as well as computational simulation. Remarkably, compared with the cured bulk elastomers and matrix(M)/SiO₂blends, M/particle brushes (PB) exhibit significant improvement in mechanical properties, including tensile strength, elongation at break, modules, and rolling resistance. This elastomer nanocomposites afford a novel prospect for the practical application of next‐generation automobile tires with enhanced performance. 

Abstract Brillouin light scattering and elastodynamic theory are concurrently used to determine and interpret the hypersonic phonon dispersion relations in brush particle solids as a function of the grafting density with perspectives in optomechanics, heat management, and materials metrology. In the limit of sparse grafting density, the phonon dispersion relations bear similarity to polymer‐embedded colloidal assembly structures in which phonon dispersion can be rationalized on the basis of perfect boundary conditions, i.e., isotropic stiffness transitions across the particle interface. In contrast, for dense brush assemblies, more complex dispersion characteristics are observed that imply anisotropic stiffness transition across the particle/polymer interface. This provides direct experimental validation of phonon propagation changes associated with chain conformational transitions in dense particle brush materials. A scaling relation between interface tangential stiffness and crowding of polymer tethers is derived that provides a guideline for chemists to design brush particle materials with tailored phononic dispersion characteristics. The results emphasize the role of interfaces in composite materials systems. Given the fundamental relevance of phonon dispersion to material properties such as thermal transport or mechanical properties, it is also envisioned that the results will spur the development of novel functional hybrid materials. 

Abstract Liquid‐metal embedded elastomers (LMEEs) have been demonstrated to show a variety of excellent properties, including high toughness, dielectric constant, and thermal conductivity, with applications across soft electronics and robotics. However, within this scope of use cases, operation in extreme environments – such as high‐temperature conditions – may lead to material degradation. While prior works highlight the functionality of LMEEs, there is limited insight on the thermal stability of these soft materials and how the effects of liquid metal (LM) inclusions depend on temperature. Here, the effects on thermal stability, including mechanical and electrical properties, of LMEEs are introduced. Effects are characterized for both fluoroelastomer and other elastomer‐based composites at temperature exposures up to 325 °C, where it is shown that embedding LM can offer improvements in thermo‐mechanical stability. Compared to elastomer like silicone rubber that has been previously used for LMEEs, a fluoroelastomer matrix offers a higher dielectric constant and significant improvement in thermo‐mechanical stability without sacrificing room temperature properties, such as thermal conductivity and modulus. Fluoroelastomer‐LM composites offer a promising soft, multi‐functional material for high‐temperature applications, which is demonstrated here with a printed, soft heat sink and an endoscopic sensor capable of wireless sensing of high temperatures. 

Unlike inorganic nanoparticles, organic nanoparticles (oNPs) offer the advantage of “interior tailorability,” thereby enabling the controlled variation of physicochemical characteristics and functionalities, for example, by incorporation of diverse functional small molecules. In this study, a unique inimer-based microemulsion approach is presented to realize oNPs with enhanced control of chemical and mechanical properties by deliberate variation of the degree of hyperbranching or cross-linking. The use of anionic cosurfactants led to oNPs with superior uniformity. Benefitting from the high initiator concentration from inimer and preserved chain-end functionality during atom transfer radical polymerization (ATRP), the capability of oNPs as a multifunctional macroinitiator for the subsequent surface-initiated ATRP was demonstrated. This facilitated the synthesis of densely tethered poly(methyl methacrylate) brush oNPs. Detailed analysis revealed that exceptionally high grafting densities (~1 nm⁻²) were attributable to multilayer surface grafting from oNPs due to the hyperbranched macromolecular architecture. The ability to control functional attributes along with elastic properties renders this “bottom-up” synthetic strategy of macroinitiator-type oNPs a unique platform for realizing functional materials with a broad spectrum of applications.