Monomer concentration fluctuations in high molecular weight polymer blends are investigated. The fluctuations reduce the value of the χ interaction term in the Flory-Huggins free energy by a factor of (1 - 6/π2) and add a concentration and molecular weight contribution which decreases phase stability for off-critical compositions. Except at the critical point, the spinodal values are smaller than those predicted from a Flory-Huggins-type free energy. For an incompressible blend with components of equal size N, the corrections to the spinodal were found to vary as |1 - 2φ0| 4/3N-1/3, where φ0 is the mean concentration.
ASJC Scopus subject areas
- General Physics and Astronomy
- Physical and Theoretical Chemistry