PREDICTION OF INTERFACIAL-TENSION OF IMMISCIBLE POLYMER PAIRS USING ASQUARE GRADIENT THEORY COMBINED WITH THE FOV EQUATION-OF-STATE FREE-ENERGY EXPRESSION

Interfacial tension between polystyrene and polybutadiene is predicted by using a square gradient theory in conjunction with the Flory-Orvol l-Vrij equation-of-state expression for the free energy of mixing. The equation-of-state interaction parameter is determined by fitting the theory to the experimental cloud points. The square gradient coefficie nt is also calculated by the relation derived from a scattering functi on. The combined theory for interfacial tension predicts a magnitude a nd temperature dependence of interfacial tension although no adjustabl e parameter is used in calculating interfacial tension. The molecular weight dependence of interfacial tension is also predicted, and well d escribed by a relation gamma=gamma(infinity)+CMn-z where z=2/3 for low molecular weight species and z=1 for higher molecular weight species. (C) 1998 Elsevier Science Ltd. All rights reserved.