An approximate method for the determination of polymer–polymer interaction parameters of incompatible polymers in solution

A method is developed, based on Scott's equations for ternary systems of two polymers and a mutual solvent, for the calculation of values of the polymer–polymer interaction parameter, χ23, for systems in which both polymer–solvent interaction parameters χ12 and χ13 are not known a priori. Equilibrium phase studies were carried out on ternary systems of polystyrene, polybutadiene, and tetrahydrofuran or toluene at 23°C and 1 atm. Typical interaction parameter values (χ23) calculated by this new method were compared with the values of χ23 determined earlier using standard equations and known χ12 values for these systems, and were found to agree very well. It is concluded that the technique presented in this article can be used for mixed polymer systems in good mutual solvents where neither polymer–solvent interaction parameter is known, for determining an approximate value of the χ23 parameter alone.