QUANTITATIVE THEORY OF THE GLOBULE-TO-COIL TRANSITION .3. GLOBULE GLOBULE INTERACTION AND POLYMER-SOLUTION BINODAL AND SPINODAL CURVES IN THE GLOBULAR RANGE

In this series of papers new results and a brief review of the current state of mean-field theories of the condensed globular state and of the globule-to-coil transition in the THETA-region for a linear, homogeneous, noncharged macromolecule are presented. As a basis of our consideration, we use both Lifshitz's theory and interpolation Flory-type theory. Complete quantitative theoretical results are obtained and compared with experimental data. In this paper (the third in this series) we analyze quantitatively interactions between chains in a poor solvent. At first we calculate density distributions and the interaction free energy for two globules equilibrated at an arbitrary distance zeta from each other; a special method has been used for this calculation based on the introduction of two auxiliary uniform fields which do not perturb the globules' inner structures but fix the value of zeta. Then we calculate the corresponding pair virial coefficient and the coexistence binodal curve on the T-c plane in the second virial approximation. We estimate also the spinodal T-c curve.