Molecular dynamics simulations of amorphous polymer surfaces : Modeling vs experiments

Molecular dynamics simulations have been carried out on fully atomistic models of amorphous polymers. Both bulk structures and thin films were simulated for a wide range of thermoplastics such as PS, PMMA, poly(phenylene-ether) (PPE), poly(etherimide) (PEI), and polyethersulfone (PES). The influence of molecular weight and of the presence of functional end-groups was investigated. PVT (Pressure- Volume-Temperature) measurements have been conducted, as another method to compute physical properties of amorphous polymers. From such measurements, cohesive energy densities, interaction parameters, and then interfacial properties, were obtained for the various thermoplastics and the corresponding incompatible pairs. These data were compared with those obtained by the pendant drop method, which allows for direct measurements of surface and interfacial tensions of polymers in the molten state.