Yulong Chen

United-atom molecular dynamics simulations were performed to investigate the structure, dynamics, and mechanical-viscoelastic properties of natural rubber (NR)/Eucommia ulmoides gum (EUG) blends. The systems were modeled as fully amorphous matrices to isolate the intrinsic behavior of the disordered phase. Results reveal that incorporating rigid EUG chains into flexible NR induces a counterintuitive acceleration of segmental dynamics─manifested as a decreased glass transition temperature and enhanced chain diffusion─driven by local segmental ordering that facilitates chain sliding. Under uniaxial deformation, tensile strength exhibits a nonmonotonic composition dependence, with optimal reinforcement at 20% EUG content, arising from a balance between the orientational reinforcement of rigid segments and the delayed onset of cavitation. Linear viscoelastic analysis shows that enhanced dynamics shift the α-relaxation peak to higher frequencies and slightly increase energy dissipation. This contrasts with the reduced hysteresis reported for real materials, a discrepancy that stems from the absence of crystalline constraints and chemical cross-links in our amorphous models. By delineating the intrinsic role of amorphous-phase dynamics, this work provides molecular-level insights into the structure–property relationships of biobased elastomers.

Overcoming the trade-off between electromagnetic interference (EMI) shielding and mechanical flexibility remains a critical challenge for advanced electronics. Herein, we design flexible ethylene propylene diene monomer (EPDM) nanocomposites incorporating one-dimensional copper nanowires (CuNWs) and two-dimensional pyrrole-modified MXene (PPy-MXene). The PPy modification significantly improves the dispersion and interfacial compatibility of MXene within the rubber matrix, while the high-aspect-ratio CuNWs synergistically construct an efficient 1D/2D interpenetrating conductive network with PPy-MXene at an ultralow total filler loading of only 6 wt%. Benefiting from this structural synergy, the composite achieves an outstanding balance of EMI shielding, conductivity, and mechanical robustness. Specifically, the composite filled with 1 wt% PPy-MXene and 5 wt% CuNWs exhibits a practical EMI shielding effectiveness of 28.35 dB in the X-band, satisfying the commercial requirement (>20 dB) and outperforming single-filler systems at the same total loading. Remarkably, the composite retains exceptional elastomeric characteristics with a tensile strength of ∼14 MPa and an elongation at break exceeding 600%. This work provides an effective strategy to circumvent the typical electrical-mechanical trade-off in elastomers, paving the way for flexible EMI shielding applications.

Carbon black (CB) is the most important and commonly used reinforcing filler in the rubber industry. However, it is easy to agglomerate to form filler networks, restricting the improvement of the mechanical properties of the rubber composites. Here, we developed a method to modify the surface of CB via hydroxylation and silane coupling, which promotes dispersion and consequently improves the mechanical performance of rubber composites. The static and dynamic mechanical properties of the composites were evaluated using uniaxial tensile testing, dynamic thermomechanical analysis (DTMA), and dynamic compression fatigue testing. Our results showed that under an adequate hydroxylation condition, the mechanical strength of the composites could be increased by about 40% without sacrificing the fracture toughness, and the abrasion resistance could be improved by about 18%. Meanwhile, an appropriate modification of CB would also increase the dynamics hysteresis at 0°C and decrease that at 60°C synchronously. As the dynamics hysteresis at high temperature decreased, the dynamic heat build‐up was reduced (by about 14%) without significantly affecting the dynamic permanent set. These findings highlight the potential of surface‐modified CB in enhancing the performance of rubber composites, providing valuable insights for the development of high‐performance rubber materials.

The inclusion of sacrificial hydrogen bonds is crucial for advancing high-performance rubber materials. However, the molecular mechanisms governing the impact of these bonds on material properties remain unclear, hindering progress in advanced rubber material research. This study employed all-atom molecular dynamics simulations to thoroughly investigate how hydrogen bonds affect the structure, dynamics, mechanics, and linear viscoelasticity of rubber materials. As the modified repeating unit ratio (β) increased, both interchain and intrachain hydrogen bond content rose, with interchain bonds playing a predominant role. This physical cross-linking network formed through interchain hydrogen bonds restricts molecular chain movement and relaxation and raises the glass transition temperature of rubber. Within a certain content of hydrogen bonds, the mechanical strength increases with increasing β. However, further increasing β leads to a subsequent decrease in the mechanical performance. Optimal mechanical properties were observed at β = 6%. On the other hand, a higher β value yields an elevated stress relaxation modulus and an extended stress relaxation plateau, signifying a more complex hydrogen-bond cross-linking network. Additionally, higher β increases the storage modulus, loss modulus, and complex viscosity while reducing the loss factor. In summary, this study successfully established the relationship between the structure and properties of natural rubber containing hydrogen bonds, providing a scientific foundation for the design of high-performance rubber materials.