Flory–Huggins solution theory

A lattice-based thermodynamic model of polymer solutions that describes mixing free energy through combinatorial entropy and an interaction parameter.

Flory–Huggins free energy: The free-energy-of-mixing expression combining lattice combinatorial entropy with an enthalpic interaction term. It is the equation at the center of the theory’s predictions.
Polymer: A substance made of macromolecules whose structures consist of repeated chemical units. The theory addresses the mixing behavior of long polymer chains.
Polymer miscibility: The capacity of two polymers to form a single homogeneous phase over specified conditions. The interaction parameter provides a simple criterion for whether polymer-rich mixtures tend to separate.
Flory–Rehner theory: A theory of polymer gels combining network elasticity with the free energy of polymer–solvent mixing. It extends Flory–Huggins mixing thermodynamics to swelling of cross-linked networks.
Flory–Huggins interaction parameter: A dimensionless parameter representing the energetic preference for unlike contacts over like contacts in a lattice mixture. Its value determines whether energetic effects favor mixing or separation.
Polymer solution: A homogeneous or phase-separated mixture of polymer chains and a solvent. This is the class of mixtures the theory was built to describe.
Solvent quality: A measure of how favorably a solvent interacts with a polymer and expands or contracts its chains. The model relates polymer–solvent interactions to conditions favoring swollen coils or collapsed chains.
Flory–Krigbaum theory: A polymer-solution theory that accounts for nonuniform segment density around polymer coils. Its coil-based treatment relaxes the uniform lattice-mixture picture.
Combinatorial entropy: Entropy arising from the number of distinct ways components can be arranged. The theory counts polymer and solvent arrangements to obtain its mixing-entropy term.
Lattice model: A model that represents space as discrete sites occupied by particles or molecular units. The theory simplifies molecular packing by assigning segments and solvent molecules to lattice sites.

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