INFLUENCE OF CONFORMATIONAL ASYMMETRY ON THE SURFACE ENRICHMENT OF POLYMER BLENDS .2.

We reexamine the influence of statistical segment length asymmetry on the surface segregation of homopolymer blends in a mean field thread model of polymer melts. By developing numerical self-consistent field solutions of the Edwards-Helfand equations, we demonstrate that the component with the smaller value of the parameter beta(2) = alpha(2)/(6v) (a is the statistical segment length and v is the segment volume) is enriched at a neutral, impenetrable surface. Qualitatively, this finding is in agreement with our earlier analytical work and with experiment. However, in contrast to our earlier work, we find that the absolute magnitude of the segregation is a sensitive function of the chain lengths of the two species and of the compressibility of the system. (C) 1995 John Wiley and Sons, Inc.