Novel map for polymer miscibility as revealed by neutron reflectometry

During annealing, above the glass transition temperatures the interface wid th between incompatible polymers increases with time, reaching an equilibri um value (typically 2 and 15 nm), which according to mean-field theory is d etermined by the Flory-Huggins-Stavermann interaction parameter chi. The qu antity chi is a measure of polymer compatibility, although it is not well u nderstood on a molecular basis and is often used as an empirical parameter. The purpose of this work is to reveal a correlation of chemical structure and the interaction parameter chi. A novel scheme is used for a graphical r epresentation of this correlation. The interaction parameters are calculate d consistently from interfacial width values and from the compositions of c oexisting phases, accessible by neutron reflectometry. This is an important fact because interfaces might be enlarged due to capillary waves and would result in wrong values for the interaction parameter. A useful differentia l equation is presented connecting compositions of coexisting phases and in terfacial profile. (C) 2000 Elsevier Science B.V. All rights reserved.