Macromolecules, Vol.35, No.16, 6446-6454, 2002
Interface between a liquid crystalline polymer and a flexible polymer
The properties of the interfacial region between melt phases of a liquid crystalline polymer and a flexible polymer were studied using the three-dimensional bond fluctuation model. The far-field orientation has a strong effect on the magnitude of the interfacial tension and the structure of the "interphase". The interfacial tension is an increasing function of the nematic order parameter S for a parallel far field, while it is a decreasing function for a homeotropic (orthogonal) far field, with the difference in the magnitude of the interfacial tension growing exponentially in S. The interfacial tension for both far-field orientations is insensitive to liquid crystalline polymer chain length. Chain ends penetrate the adjacent phase with a homeotropic orientation, resulting in a more diffuse interphase. There is, nevertheless, a substantial orientation parallel to the interface even with a homeotropic far field, and order parallel to the interface is induced in the flexible polymer phase with both parallel and homeotropic far fields. The computed parameters for the continuum theory of nematic/isotropic interfaces lead to an "easy axis" that is orthogonal to the interface. The interfacial tension for a parallel far field scales linearly with (epsilon/k(B)T)S-1/2(2), where epsilon is the magnitude of the repulsive interaction between unlike chain segments; similar scaling is not obtained for an orthogonal far field.