Structure of inhomogeneous polymer solutions: a density functional approach

Area of Science:

• Physical Chemistry
• Polymer Science
• Statistical Mechanics

Background:

• Understanding polymer solution behavior in confined spaces is crucial for materials science and nanotechnology.
• Existing models often simplify polymer chain connectivity and interactions.
• Accurate theoretical predictions are needed to complement experimental and simulation data.

Purpose of the Study:

• To develop and validate a density functional theory for polymer solutions confined between surfaces.
• To model polymer molecules as chains of hard spheres and solvents as hard spheres.
• To investigate the density profiles of polymers and solvents under confinement.

Main Methods:

• Utilized density functional theory (DFT) with a "pearl necklace" model for polymers and hard spheres for solvent.
• Employed the universality of free energy density functional to derive the direct correlation function.
• Calculated uniform bulk fluid direct correlation function using reference interaction site model (RISM) integral equations with Percus-Yevick closure.
• Incorporated Verlet-modified bridge functions.

Main Results:

• The theoretical model successfully predicted density profiles for both polymer and solvent.
• Calculated density profiles demonstrated good agreement with established computer simulation results.
• The approach provides a robust method for analyzing confined polymer systems.

Conclusions:

• The developed density functional theory offers a reliable framework for studying confined polymer solutions.
• The "pearl necklace" model combined with DFT effectively captures key structural aspects.
• This work validates the theoretical approach against simulations, paving the way for further applications.