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Through coarse-grained molecular dynamics simulation, we have successfully designed the chemically cross-linked (fixed junction) and the slide-ring (SR) systems. Firstly, we examine the dynamic properties such as the mean-square displacement, the bond, and the end-to-end autocorrelation functions as a function of the cross-linking density, consistently pointing out that the SR system exhibits much lower mobility compared with the fixed junction one at the same cross-linking density. This is further validated by a relatively higher glass transition temperature for the SR system compared with that of the fixed junction one. Then, we calculated the effect of the cross-linking density on the stretch-recovery behavior for the SR and fixed junction systems. Although the chain orientation of the SR system is higher than that of the fixed-junction system, the tensile stress is smaller than the latter. We infer that much greater chain sliding can occur during the stretch, because the movable ring structure homogeneously sustains the external force of the SR system, which, therefore, leads to much larger permanent set and higher hysteresis during the recovery process compared with the fixed-junction one. Based on the stretch-recovery behavior for various cross-linking densities, we obtain the change of the hysteresis loss, which is larger for the SR system than that of the fixed junction system. Lastly, we note that the relatively bigger compressive stress for the SR system results from the aggregation of the rigid rings compared with the fixed junction system. In general, compared with the traditionally cross-linked system, a deep molecular-level insight into the slide-ring polymer network is offered and thus is believed to provide some guidance to the design and preparation of the slide-ring polymer network with both good mechanical and damping properties.

The structure-property relationship of polymer nanocomposites (PNCs) has been extensively investigated, but less effort has been devoted to studying the effect of chain architectures. Herein, through coarse-grained molecular dynamics simulation, we build six different chain architectures namely linear, branch-2 (with two side chains), branch-4 (with four side chains), branch-10 (with ten side chains), star-4 (with four arms) and star-6 (with six arms), by fixing the molecular weight per chain. First, we examine the effect of the interfacial interaction between the polymer and nanoparticles (NPs) ε on the dispersion of NPs, by calculating the radial distribution function between NPs, the second virial coefficient and the average number of neighbor fillers. We observe a non-monotonic change of the NP dispersion as a function of ε for all PNCs with different chain architectures, indicating the optimal dispersion of NPs at moderate ε. Meanwhile, we find that the star-6, branch-4 and linear chains promote the best dispersion of NPs at moderate ε, compared to the other chain architectures. Then we investigate the strain hardening behavior and chain orientation of these PNCs under uniaxial tension. We find that the star-6 chains demonstrate relatively the most remarkable reinforced mechanical behavior of PNCs. Furthermore, we probe the effect of end-functionalization of polymer chains with different architectures on the dispersion of NPs, by comparing them to the case without any functionalization. We find that the introduction of the end-functionalization benefits mostly the high degree of chain branching for promoting the dispersion of NPs. Meanwhile, we observe that when the tensile strain is small, the branch-4 structure shows relatively improved mechanical properties, however, when the tensile strain is large, the star-6 and branch-10 structures display the best mechanical properties, and the end-functionalization evidently improves the mechanical properties of the PNCs. Our simulation results provide guidelines to tailor the dispersion of NPs and the mechanical properties of PNCs, by taking advantage of the chain architecture and its end-functionalization strategy.