Phase behavior of ternary systems involving a conformationally variable chain and a randomly coiled polymer: Effect of external orientational field

The lattice theory regarding ternary systems involving a conformationally variable polypeptide and a randomly coiled polymer presented recently is extended to the case where an external orientational field of quadrupole type is present. The mixing partition function is elaborated by inclusion of the energy term arising from the external field to the lattice scheme previously developed. The calculations carried out show that the external field exerts a marked effect on the phase behavior of the ternary systems. The isotropic-anisotropic biphasic gap is predicted to shift to lower polymer concentrations and becomes narrower when the external field exists. The entrance of the randomly coiled polymers into the anisotropic phase is promoted. Influences of the external field intensity, molecular structure parameters, and compositions have also been studied.