Electron tomography as a structural bridge: Linking interfacial engineering to macroscopic viscoelasticity in silica/rubber nanocomposites

Abstract

The interface engineering and dispersion research of nanocomposites have universal applications in flexible electronic materials, intelligent damping materials, and green tire materials. The green tire necessitates rubber composites with low rolling resistance and environmental compatibility, wherein the three-dimensional dispersion and interfacial design of nanofillers play a pivotal role. By integrating electron tomography-based 3D quantification-capable of resolving nanoscale agglomerate compactness, branching, and connectivity-the limitations of conventional 2D microscopy are overcome, revealing a dual-phase dispersion transition modulated by grafting degrees of 3-mercaptopropyl-ethoxy-bis (tridecyl-pentaethoxy-siloxane (Si747), a low-VOC silane coupling agent with shielded alkoxy groups and physical adsorption dual interfacial interactions. At low grafting degrees (0 %–5 %), silica (SiO₂) agglomerates exhibited reduced compactness (26 % decrease in V_silica/V_effect) but increased branching (N_BN/N_TN from 0.643 to 2.17) and connectivity (L_seg doubled), where energy loss is dominated by cyclic breakdown/reformation of filler networks leading to enhanced Payne effect and elevated tan δ at 60 °C. At higher modification level (grafting degrees 5 %–15 %), ET visualized the disassembly of agglomerates, with a 67 % surge in isolated primary nanoparticles, accompanied by weakened connectivity. Consequently, energy dissipation shifts from filler network breakdown to viscoelastic deformation within the interfacial layer, thereby minimizing overall energy loss. This work challenges conventional paradigms of silica modification and reveals the two-stage mechanism of interfacial modification on dispersion and viscoelasticity from the perspective of 3D dispersion of fillers.