Coarse-grained molecular dynamics simulation of cis-1,4-polyisoprene with silica nanoparticles under extreme uniaxial tension

Abstract

Coarse-grained (CG) cis-1,4-polyisoprene (PI) models with multiple silica nanoparticles (NPs) are built to study the effect of NPs and crosslinks in the uniaxial tensile simulation. The potential functions of the CG models are obtained mainly via the iterative Boltzmann inversion method. The tensile simulation results show that the grafted silica NPs and the crosslinked structure play reinforcing roles while the smooth silica NPs do the opposite, which have the similar trends with the experiment results. The differences of mechanical properties for these models are studied from different microscopic aspects, such as the network of NPs, the bond lengths, the free molecular chains, the entanglements, the stress and strain distribution and the microvoid evolution. As a result, the main reasons for the weakening of PI models with smooth silica NPs come from the weak interfacial interaction, the inhomogeneity of structural deformation and the reduction of the number of entanglements. However, if there are graft chains, the interfacial interaction can be enhanced by entangling with the matrix molecular chains. The graft chains can make it possible for the aggregated NPs to separate and can hinder the growth of microvoids at the interface. In addition, the inconsistency of the stress and strain distributions at the microscopic level is verified and the nucleation mechanism of microvoids is believed to be caused by the local violent movement of molecular chains.

Approaches and Perspective of Coarse-Grained Modeling and Simulation for Polymer–Nanoparticle Hybrid Systems

“…The CG model of a silica nanoparticle-impregnated cis -1,4-polyisoprene polymer was built to study the effect of nanoparticles and cross-links in the uniaxial tensile simulation. 121 The results of this study showed that the polymer-grafted silica nanoparticles and the cross-linked structure play reinforcing roles, while the smooth nanoparticles do the opposite, which was in line with the experiment results. Further, the same group investigated the effects of silica/carbon black hybrid nanoparticles on the viscoelastic properties of uncross-linked cis -1,4-polyisoprene rubber.…”

“…More recently, the IBI approach has been used to generate the CG models of silica nanoparticles in a polymer matrix. The CG model of a silica nanoparticle-impregnated cis -1,4-polyisoprene polymer was built to study the effect of nanoparticles and cross-links in the uniaxial tensile simulation . The results of this study showed that the polymer-grafted silica nanoparticles and the cross-linked structure play reinforcing roles, while the smooth nanoparticles do the opposite, which was in line with the experiment results.…”

Ionic Polymer Nanocomposites Subjected to Uniaxial Extension: A Nonequilibrium Molecular Dynamics Study

“…The NP volume fraction had an effect on the stress-strain behavior of the nanocomposite due to the network formed between polymers and nanofillers; in particular, the stress increased with NP volume fraction in the linear elastic regime (at 10% strain), and the higher surfaceto-volume ratio of the NPs was attributed to contribute to the mechanical improvement of the nanocomposite [27]. Moreover, the grafting of NPs with polymers was reported to also reinforce the nanocomposite and increase the elastic constants [28][29][30]. It was also found that strain hardening was only weakly affected by grafting density or NP size [31].…”

Fracture in Silica/Butadiene Rubber: A Molecular Dynamics View of Design–Property Relationships

“…Molecular simulations of PNCs have increased significantly in recent years, as their complexity can now be approached thanks to advances in high-performance computing. − Molecular dynamics (MD) and other particle-based mesoscale methods − are well suited to explore the behavior of these materials, revealing details that are not readily accessible to experiments. Today, most MD simulation of rubbery PNCs are still carried out with generic coarse-grained models, which aim at simplicity and a general understanding, rather than quantitative, predictive modeling. − Despite their greater complexity, in recent years there have been some notable atomistic (i.e., chemically detailed) simulations of silica-filled rubber networks, − which in principle may be used to address system-specific questions.…”

“…Today, most MD simulation of rubbery PNCs are still carried out with generic coarse-grained models, which aim at simplicity and a general understanding, rather than quantitative, predictive modeling. 33 − 39 Despite their greater complexity, in recent years there have been some notable atomistic (i.e., chemically detailed) simulations of silica-filled rubber networks, 40 − 42 which in principle may be used to address system-specific questions.…”