Structure and dynamics of poly(methyl methacrylate)/graphene systems through atomistic molecular dynamics simulations

Abstract

The main goal of the present work is to examine the effect of graphene layers on the structural and dynamical properties of polymer systems. We study hybrid poly(methyl methacrylate) (PMMA)/graphene interfacial systems, through detailed atomistic molecular dynamics (MD) simulations. In order to characterize the interface, various properties related to density, structure and dynamics of polymer chains are calculated, as a function of the distance from the substrate. A series of different hybrid systems, with width ranging between [2. 60 -13.35] nm, are being modeled. In addition, we compare the properties of the macromolecular chains to the properties of the corresponding bulk system at the same temperature. We observe a strong effect of graphene layers on both structure and dynamics of the PMMA chains. Furthermore the PMMA/graphene interface is characterized by different length scales, depending on the actual property we probe:Density of PMMA polymer chains is larger than the bulk value, for polymer chains close

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

“…The preference of the chain ends to stay close to the surface, compared to the rest of the monomers, has been reported in previous studies of polymer/surface interfaces and it is primary of entropic origin [17]. We have also observed this behavior in our previous studies at the polymer/graphene interface of polymer thin films confined between two "infinite" (periodic) graphene sheets, as well as at polymer/vacuum interface [20,21,26]. A similar analysis has been performed in our current systems for both the end and the inner monomers.…”

“…However, the same would be the case if someone has used slabs (instead of spheres) as in the case of the analysis of polymer/solid interfaces with periodic-infinite solid surfaces. Only for the later system the parallel to the surface slabs is a natural way to calculate local properties due to the periodicity [18,20,21]. Below, for the infinite graphene sheet we compare polymer chain density profile through both ways of analysis.…”

“…In our previous works, we have extensively studied the properties of various polymer/graphene interfaces through atomistic simulations in which infinite (periodic) graphene sheets were assumed [18,20,21]. The current work is focused on the properties of polyethylene/graphene nanocomposites with graphene sheets of various sizes.…”

Development of an Ultrafast Low-Energy Electron Diffraction Setup

“…In particular, whereas the polymer, atactic PMMA, usually does not exist in crystalline form, graphene is a highly-ordered system. Moreover, while individual PMMA chains with molecular weights of close to 10 6 g/mol are expected to react rather slowly on environmental changes [221], graphene's relaxation dynamics have been shown to happen on very short time scales [203,222].…”

“…Qualitatively, it can be reasoned that the strong template properties of the graphene only result in superstructure formation on the PMMA layer in direct contact with it [221].…”