A molecular dynamics study of PEO between GO layers

Resumen del trabajo presentado al 7th International Discussion Meeting on Relaxations in Complex Systems: "New results, Directions and Opportunities", celebrado en Barcelona (España) del 21 al 26 de julio de 2013.The dynamic behaviour of a polymer nanocomposite material: Poly (ethylene oxide) (PEO) confined in graphite oxide (GO) layers (interlayer distance of about 7.5 angstrom) is studied in this work by means of atomistic molecular dynamics simulations performed with the COMPASS forcefield. This forcefield has previously been tested by us during recent years to produce an excellent mimic of the dynamic behaviour of this polymer both in bulk as well as in its blend (PEO 20 w%) with poly (methyl methacrylate) PMMA. This latter system could be considered as an example of confinement for PEO due to the much reduced mobility of PMMA at the studied temperatures. In the work we present here, we confine PEO in thin films sandwiched by GO and use a similar methodology as in the previous works to study its modified dynamics. However, due to the different nature of this new system with respect to bulk polymers or blends, care was taken to grant that the COMPASS forcefield (which is mainly aimed to be used within polymeric systems) can also describe faithfully the interactions between the PEO polymer and the GO film substrate. This had previously been done by comparing such interactions with others calculated by means of Density Functional Theory of different levels of accuracy. We discuss the results obtained in terms of the atomic mean-squared displacements, self van Hove correlation function, incoherent scattering function and hydrogen bonding between PEO and GO defects.Peer Reviewe