Manipulating the mechanical properties of cis-polyisoprene nanocomposites via molecular dynamics simulation

Attributed to the reinforcing effect of the NPs, filled natural rubber (NR) exhibits more excellent mechanical properties compared to pure natural rubber and has been attracting considerable scientific and technological attention. However, only a few studies have shown a systematical understanding of the structure-mechanics relation of filled natural rubber. Herein, a common strategy used to study the effects of the critical structural factors on strain-induced crystallization (SIC) and mechanical properties at the molecular level is to adopt molecular dynamic simulation (MD). Increasing the cross-linkage of the polymer matrix improves the entanglement degree, and the mechanical properties are reinforced by the high orientation of the polymer chains due to the high entanglement degree and the dissipation of energy due to the unentangling. Surprisingly, we find that the stress-strain behaviour of filled natural rubber is significantly manipulated by nanoparticle (NP) content, size and strength of interfacial interaction, evidenced by the increase of the chain orientation, SIC, and energy dissipated by NPs and polymer matrix, compared with the case of pure natural rubber. The underlying mechanism is the adsorption of the polymer by NPs, which leads to the orientation and crystallization of the polymer chains induced by NPs during the deformation process and energy dissipation through the slip of NPs and polymer chains. In general, this work demonstrates a detailed molecular-level structure-mechanics relation of filled natural rubber and provides some rational guidelines for experimentally designing and fabricating high-performance elastomer nanocomposites.