(540e) Elucidating the Molecular Origins of Reinforcement in Filled Elastomers Via Spatial- and Species-Resolved Stresses from Molecular Dynamics Simulations

Despite the use of nanoparticles as mechanical reinforcing agents in elastomers for approximately a century, the precise mechanism of reinforcement in elastomeric nanocomposites under nonlinear deformation remains unresolved. Evidence over several decades has suggested that the Payne effect, which marks the onset of a profoundly nonlinear regime of elastomeric mechanical response on the order of 10% strain, emerges from breakdown of a percolated filler network at lower strains. Beyond this point, the mechanical response of elastomeric nanocomposites reflects a pronounced dissipative character. However, the exact origins of the filler percolation and of the post-Payne dissipative response – for example, whether dominated by filler friction, ‘glassy bridge’ effects, or bridging chain reflects – is not settled and remains subject to debate. A better understanding of the molecular mechanisms controlling reinforcement in elastomeric nanocomposites could inform design of new tough elastomeric materials with better tunable properties.

Here we describe the results of large-scale molecular dynamics simulations probing nonlinear mechanical response of elastomeric nanocomposites under extensional deformation. We particularly probe reinforcement effects in elastomers filled with structured nanoparticles prone to yielding high deformation effects. We report on calculation of local mechanical response properties within the composite, providing information on the precise spatiotemporal origins of nonlinear reinforcement. These data shed light on the relative roles of the mechanisms discussed above and extend the understanding of nanofiller percolation effects beyond the linear deformation regime. Given that elastomeric nanocomposite are an archetypal material for a much broader class of soft ‘dual solids’ comprised of co-percolating rigid and soft domains, these results may have broader implications for the understanding of mechanical response in these materials.

This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Award Number DE-SC0022329.