Determination of the Mechanical Properties of a Poly(methyl methacrylate) Nanocomposite with Functionalized Graphene Sheets through Detailed Atomistic Simulations

Abstract

Recent experimental studies have demonstrated that the introduction of oxygen-containing functional groups in graphene sheets can greatly enhance the mechanical properties of their nanocomposites with polar polymers even at extremely low loadings. Motivated by these reports, we determine here the elastic constants of syndiotactic poly(methyl methacrylate) (sPMMA) at small wt % loadings of graphene sheets through atomistic modeling. To carry out a comparative study of the effect of graphene functionalization on the degree of mechanical reinforcement, we address both pure (i.e., unfunctionalized) and functionalized graphene sheets bearing epoxy and hydroxyl groups randomly bound on both sides of their surface in the host sPMMA matrix. The calculation of elastic constants (which involves no adjustable parameters) follows the methodology originally proposed by Theodorou and Suter [Macromolecules198619139], and has been based on the use of the Dreiding all-atom force-field. Our predictions for the elastic constants (which for the pure sPMMA matrix are within the error bars of experimentally computed values) suggest a substantial increase in the elastic constants, especially in the case of functionalized graphene sheets. For example, at just 5.67 wt % loading of the host matrix in functionalized graphene sheets, they indicate an improvement in Young’s modulus E by ∼74%, in the bulk modulus B by ∼19%, and in the shear modulus G by 83%. Our results fully corroborate recent experimental measurements about the unique opportunities that functionalized graphene sheets offer for the design of new, very strong multifunctional materials at low nanofiller content.

Structural and Dynamical Properties of Polyethylene/Graphene Nanocomposites through Molecular Dynamics Simulations

“…Many simulation and experimental studies [1,[6][7][8][9][10][11][12][13][14][15][16][17][18][19] explore the influence of the chemical functionalization of graphene on the various properties of the nanocomposites. For example, Konatham et al [14] presented results based on atomistic Molecular Dynamics simulations combined with coarse grained Monte Carlo simulations, focused on graphene sheets dispersed in n-octane.…”

“…They also mention the effect of the size of the graphene sheets, though their atomistic simulations are limited to rather small sheets. More recently Skoutzos et al [15] presented results for syndiotactic poly(methyl methacrylate)/graphene nanocompostites, based on atomistic Molecular Dynamics simulations. They found that the introduction of oxygen-containing functional groups in graphene sheets leads to a great enhancement of the mechanical properties of the hybrid system, even at extremely low loading.…”

Heterogeneities in Polymer Structural and Dynamic Properties in Graphene and Graphene Oxide Nanocomposites: Molecular Dynamics Simulations

“…The maximum density appears somewhere between 0.4 and 0.5 nm from the nanofiller that is a common observation for polymer/G systems. This is mainly due to the adsorption of polymer by the nanofiller . Note that since polymer chains embedded the nanofiller in all directions ( x , y , and z ) in such a way that the box lateral dimension is slightly larger than the nanofiller surface, the density does not reach 0 at z = 0, for better imagination see Figure .…”

Atomistic modeling of graphene/hexagonal boron nitride polymer nanocomposites: a review

“…Recently, Skountzos et al predicted the mechanical properties of syndiotactic PMMA (sPMMA) with varying weight fraction of pristine and functionalized graphene sheets (FGS). Their simulations showed a tremendous increase in the elastic constants (Young's modulus by ~74%, bulk modulus by ~19%, and shear modulus by ~83%), with the FGS.…”