title: Dynamics and Structure of Monolayer Polymer Crystallites on Graphene.
abstract: Graphene-based nanostructured systems and van der Waals heterostructures comprise a material class of growing technological and scientific importance. Joining materials with vastly different properties, polymer/graphene heterosystems promise diverse applications in surface and nanotechnology, including photovoltaics or nanotribology. Fundamentally, molecular adsorbates are prototypical systems to study confinement-induced phase transitions exhibiting intricate dynamics, which require a comprehensive understanding of the dynamical and static properties on molecular time and length scales. Here, we investigate the dynamics and the structure of a single polyethylene chain on free-standing graphene by means of molecular dynamics simulations. In equilibrium, the adsorbed polymer is orientationally linked to the graphene as two-dimensional folded-chain crystallite or at elevated temperatures as a floating solid. The associated superstructure can be reversibly melted on a picosecond time scale upon quasi-instantaneous substrate heating, involving ultrafast heterogeneous melting via a transient floating phase. Our findings elucidate time-resolved molecular-scale ordering and disordering phenomena in individual polymers interacting with solids, yielding complementary information to collective friction and viscosity, and linking to recent experimental observables from ultrafast electron diffraction. We anticipate that the approach will help in resolving nonequilibrium phenomena of hybrid polymeric systems over a broad range of time and length scales.
authors: 4th Physical Institute - Solids and Nanostructures, University of Göttingen , 37077, Göttingen, Germany.
authors: Max
authors: M
authors: Gulde
authors: Institute of Applied and Computational Mathematics, Foundation for Research and Technology Hellas , 71110 Heraklion, Crete, Greece.
authors: Anastassia N
authors: AN
authors: Rissanou
authors: Institute of Applied and Computational Mathematics, Foundation for Research and Technology Hellas , 71110 Heraklion, Crete, Greece.|Department of Mathematics and Applied Mathematics, University of Crete , 71409, Heraklion, Crete, Greece.
authors: Vagelis
authors: V
authors: Harmandaris
authors: Institute for Theoretical Physics, University of Göttingen , 37077, Göttingen, Germany.
authors: Marcus
authors: M
authors: Müller
authors: 4th Physical Institute - Solids and Nanostructures, University of Göttingen , 37077, Göttingen, Germany.
authors: Sascha
authors: S
authors: Schäfer
authors: 4th Physical Institute - Solids and Nanostructures, University of Göttingen , 37077, Göttingen, Germany.
authors: Claus
authors: C
authors: Ropers
keywords: Polymer; crystallite; dynamics; floating solid; graphene; two-dimensional phase