## 2 Results and Discussion
### Nonlinear Rheological Behavior
It could be seen that when \(\gamma\) = 0.05%, the \(G^{\prime}\)/\(G^{\prime}_{0}\) of the SBR and NR + SBR physical blends and the NR/SBR (50/50), (25/75) blends keep almost constant, and that the \(G^{\prime}\)/\(G^{\prime}_{0}\) of the NR and NR/SBR (75/25) blend increases slightly, where \(G^{\prime}_{0}\) is the initial  
Figure 7: (a) \(G^{\prime}/G^{\prime}_{0}\) and (b) \(G^{\prime\prime}/G^{\prime\prime}_{0}\) as a function of \(\gamma\) for NR/SBR blends (symbols) and NR + SBR physical blends (dashed lines) during a loading–unloading cycle at 100 \({}^{\circ}\)C and 1 rad/s. The solid lines are predicted by numerical addition results of neat NR and SBR. Here, N is also the vertically shifting factor for the normalized moduli. The arrows indicate the loading and unloading processes. modulus. When the strain is switched to 50%, the \(G^{\prime}\)/\(G^{\prime}\)\({}_{0}\) of all the samples decays rapidly, corresponding to the transition from the solid-like to liquid-like characteristics [46]. The attenuation amplitude of NR/SBR blends decreases with increasing SBR content, and is weaker than that of NR + SBR physical blends, meaning that it is consistent with the loading-unloading experimental results shown in Figures 6 and 7. After being sheared back to \(\gamma\) = 0.05%, all the samples exhibit a gradual modulus recovery, while the NR/SBR blends show a more rapid recovery process than the NR + SBR physical blends (as shown in Figure 8c), revealing that the heterogeneous structure in NR/SBR blends may improve the reversibility of the Payne effect. In the LAOS test, the \(G^{\prime}\)\({}_{0}\) and \(G^{\prime\prime}\)\({}_{0}\) of NR are obviously higher than those of SBR, and the \(\gamma\)\({}_{\rm c}\) of NR is much smaller than that of SBR. Hence, the heterogeneous structure of NR/SBR blends may result in the heterogeneity of microscopic deformation for the NR and SBR domains. Such a phenomenon is similar with the strain amplified effect of filled rubber [47]. However, the modulus of rigid particles is far greater in that of the filled rubber and the particles are not deformed, resulting in the occurrence of stain amplification in matrix rubber. Here, the modulus difference between NR and SBR is obviously smaller than that between rigid particles and rubber. Namely, the microscopic deformation of SBR domain is larger than the macroscopic deformation of the NR/SBR blends, while the microscopic deformation of the NR domain is smaller. Hence, the modulus decay and hysteresis of the NR/SBR blend during loading is remarkably smaller than that of the numerical addition and the NR + SBR physical blend. Furthermore, the domain deformation from the equilibrium morphology of a gel-like structure to an elongated morphology under large \(\gamma\) may result in the increase in interfacial energy and then the additional contribution of  
Figure 8: \(G^{\prime}\)/\(G^{\prime}\)\({}_{0}\) as a function of lasting time for (**a**) pure NR and SBR, (**b**) NR/SBR blends and NR + SBR physical blends being sheared stepwise to \(\gamma\) = 0.05%, 50% and 0.05 at \(\omega\) = 1 rad/s. (**c**) is extracted from (**a**,**b**) for clearly showing the normalized modulus recovery process for NR, SBR, NR/SBR blends and NR + SBR physical blends at \(\omega\) = 1 rad/s from large to small strain steps (\(\gamma\) = 50% shear to \(\gamma\) = 0.05%). storage term [48; 49]. Hence, the co-continuous NR/SBR (50/50) blend with large interfacial area has the smaller modulus decay and hysteresis during the loading-unloading process.