SELF-CONSISTENT MEAN-FIELD CALCULATION OF SURFACE SEGREGATION IN A BINARY POLYMER BLEND

In this Brief Report we use a self-consistent mean-field (SCF) method to predict the surface excess (z(*)) and surface volume fraction (phi(1)) of the surface active component in a binary polymer blend. The SCF results are in excellent agreement with the measured z(*) and phi(1) values of deuterated polystyrene (dPS) in a blend of dPS and PS. However, the approach proposed by Schmidt and Binder (SB) [J. Phys. (Paris) 46, 1631 (1985)] fails to predict simultaneously z(*) and phi(1) for the same value of the excess surface free energy. A comparison of the dPS volume fraction profiles calculated by the SCF and SB models iilustrates the limitations of the SB theory as applied to the dPS-PS experiments. Using the SCF model, the excess surface free energy is shown to have a complex dependence on phi(1), in contrast to the linear behavior proposed by SB.