Classical Density Functional Theory of Polymer Fluids.

We introduce a classical density functional (DFT) description of polymer solutions, initially focusing on systems containing flexible and monodisperse chains. The theory is used to describe excluded volume effects by utilizing the so-called “Generalized Flory-Dimer” (GFD) equation of state. We also describe efficient computational approaches to numerical solutions. We then extend our treatment to describe semiflexible polymers and polydispersity. Here, the polydispersity, in combination with the well-known Schultz-Flory-Zimm molecular weight distribution, allows a different formulation for the free energy minimization. An interesting, and perhaps counterintuitive, result is that the resulting computational effort depends on the width of the molecular weight distribution, but not the average chain length. Finally, we show how the DFT can be adapted to charged oligomeric fluids displaying more complex molecular architecture. In particular, we show that the essential non-uniform structures of a model room temperature ionic liquid are accurately captured in a DFT that accounts for non-trivial bond connectivity and strongly coupled steric and electrostatic correlations.