Flory-Huggins Model for Gibbs Free Energy of Mixing in Polymer Solutions

temperature (K)

350

Flory-Huggins parameter (χ)

0

polymer length

2

number of polymers

2

The Flory–Huggins theory for polymer solutions is based on a statistical approach, in which polymer and solvent molecules occupy a regular lattice. This Demonstration shows the change in the Gibbs free energy of mixing for a polymer solution, using the equation [1]:

ΔG=RT(N

φ

1

φ

2

χ+

x

1

ln

φ

1

+

x

2

ln

φ

2

),

where

N

is the total number of lattice sites;

χ

, the Flory–Huggins parameter;

x

1

,

x

2

, the polymer mole fractions and

φ

1

,

φ

2

, the site fractions.

Use the controls to observe the dependence of the Gibbs free energy on temperature, polymer size, number of polymers and the Flory–Huggins parameter. The graph plots

ΔG

versus

φ

2

. The beaker pictures the separation of the polymer and solvent as the solution becomes immiscible. The lower diagram represents the proportion of polymers in the solution, showing the lattice in which the yellow disks represent polymer molecules and the blue disks represent solvent sites.