Tuning the visco-elasticity of elastomeric polymer materials via flexible nanoparticles: insights from molecular dynamics simulation

摘要

Tuning the viscoelasticity of polymeric materials by incorporating nanoparticles (NPs) has received considerable scientific and technological interests. Contrary to increasing the energy dissipation for damping materials, here we direct our attention to study how to decrease the energy dissipation of elastomer nanocomposites (ENCs) under periodic dynamic loading-unloading cycles. Through molecular dynamics simulation, we firstly simulate the pure cis-polybutadiene (cis-PB) system, by calculating the mean-squared end-to-end distance and the radius of gyration as a function of the chain length, the diffusion coefficient of polymer chains as a function of the temperature, the glass transition temperature, the stress-strain curves at different strain rates and temperatures, the tension-recovery and compression-recovery curves at various cross-linking densities. These results validate the accuracy of the united atom model and force-field of cis-PB. Then we show that the incorporation of flexible nanoparticles (NPs) such as graphene nanoribbons and carbon nanotubes can effectively decrease the dynamic hysteresis loss, by taking advantage of the reversible mechanical deformation of the anisotropic NPs. This effect can be further strengthened by the stronger interfacial interaction, higher loading and larger size of this kind of NPs. The underlying reason stems from the synergistic motion between the NPs and their surrounding polymer chains, leading to much smaller internal friction. This work may open up potential opportunities to fabricate high-performance polymer nanocomposites, such as energysaving ENCs tailored for tire tread.