Modeling of polymer-metal hybrid materials

Hybrid materials, where multiple substances are combined, belong to an interesting new class of materials. These materials can be optimized for specific applications and can provide a more appropriate balance between cost, weight, strength, or some other properties. Particularly interesting materials from a practical as well as a scientific perspective are the materials that combine a polymer with a metal. To understand these materials we must understand how the various substances interact with each other. In this thesis I have studied the interaction between a polymer and a metal surface at the microscopic level. I have used density-functional theory (DFT) and coarse-grained molecular dynamics to study the binding between the polymer and the metal surface. In order to provide a more realistic description for the binding of these substances I have taken into account van der Waals (vdW) interactions within DFT. My results suggest that the polymer-metal binding can be strongly affected by small amounts of doping at the interface, thus providing one way to tune the polymer-metal interface properties. Also, the vdW interaction plays a major role, and it is thus essential to include these effects when studying large molecules on surfaces. I have used the DFT results to parametrize interaction potentials for coarse-grained molecular-dynamics simulations, which I have used to study the hybrid material interface on a larger length and time scale. A hybrid simulation method which combines molecular dynamics and continuum dynamics in the same system, allows the study of even larger systems. The hybrid simulation method can also be used to equilibrate the polymer system faster than with traditional methods. Computer simulations offer the possibility to efficiently test the properties of various material combinations before committing to produce physical manifestations of these materials. These simulations can be used for providing e.g. effective boundary conditions such as friction coefficients that can be used for continuum simulations, or for simulating nanostructured composites where the interface effects dominate the bulk properties of the material.