C. Krause and B. A. Wolf

"Shear Effects on the Phase Diagrams of Solutions of highly Incompatible
Polymers in a Common Solvent 1: Equilibrium Behavior and Rheological Properties"

*Macromolecules* **1997**, *30*, 885-889.

**Abstract:** Phase diagrams (cloud points, tie lines, critical compositions)
and viscosities of homogeneous solutions were determined at temperatures ranging
from 20 to 100 degrees C for three representatives of the ternary system cyclohexanone/polystyrene/poly(n-butyl
methacrylate) [CHO/PS/PBMA] in preparation of a study on shear influences. An
only moderate increase of the two-phase region observed upon heating (LCST behavior)
witnesses little heat effects upon mixing. Tie lines which are nearly parallel
to the PS/PBMA edge of the Gibbs phase triangle indicate comparable solvent
quality of CHO for both polymers. The quantitative mathematical description
of the equilibrium behavior-required for a theoretical treatment of shear influences-was
performed on the basis of the Flory-Huggins equation by means of composition
and temperature dependent binary (integral) interaction parameters g(ij). The
present approach avoids the use of chemical potentials and minimizes the Gibbs
energy of mixing directly. Experimental data for g(CHO/PS) and g(CHO/PBMA) were
available from earlier work; g(PS/PBMA) was adjusted to reproduce the measured
phase diagram of the ternary system. Calculated and measured phase diagrams
match very well. The rheological results were used to establish a mathematical
expression describing the composition and temperature dependence of the solution
viscosities; such an equation is required for the theoretical treatment of shear
influences on the phase diagram.

preprint number: 172