MOLECULAR-WEIGHT AND POLYDISPERSITY EFFECTS AT POLYMER POLYMER INTERFACES

We study the interfacial properties of immiscible polymers, going beyond the usual approximation of infinite molecular weight, complete immiscibility. For finite molecular weights, the interfaces are broader and the interfacial tensions smaller than predicted by this approximation. These corrections are entropic effects and are significant for typical experimental situations: they are in fact inversely proportional to the incompatibility Xab, where xAB *s Flry interaction parameter between unlike (A and B) monomers and N the number of monomers per chain. In polydisperse systems, small chains accumulate slightly at the interface, lowering the interfacial tension. Our analysis seems consistent with recent interfacial tension measurements. © 1990, American Chemical Society. All rights reserved.