Hierarchical multiscale modeling of polymer-solid interfaces: Atomistic to coarse-grained description and structural and conformational properties of polystyrene-gold systems

摘要

A hierarchical simulation approach was developed in order to study polystyrene films sandwiched between two parallel Au(111) surfaces. The coarse-grained potentials describing the interaction of polystyrene with the gold surface were developed systematically using constrained all-atom molecular simulations of a styrene trimer on the Au(111) surface. The model was validated by studying a 5 nm film of short (10-mer) atactic polystyrene chains using all-atom and coarse-grained molecular dynamics simulations. The density, structure, and conformational properties of coarse-grained films were found to be in excellent agreement with all-atom ones. The coarse-grained model was then used to study the structural and conformational properties of roughly 10 and 20 nm thick films with 10-, 50-, 100-, and 200-mer chains. The width of the interphase region of the polymer films is property specific. The density profiles reached the bulk value around 1.5 nm from the interface, for all chain lengths. An estimate of the width of the interphase region based on the conformation tensor profile indicates that the interphase width is around 2-3 times the radius of gyration, which is proportional to the square root of the chain length (number of monomers), and for 200-mer chains is approximately 6-10 nm.