Surface Segregation in Binary Polymer Mixtures: A Lattice Model

Abstract

In this work, the influence of energetic effects on the structure and properties of a binary polymer-melt/surface interface has been investigated. Our interest is in the modeling of the behavior of binary, isotopic polymer blends near surfaces from a fundamental viewpoint, and to this end polymer-surface and polymer-polymer interaction energies were taken into account in the development of the model. The results of the calculations show that the component with the lower surface energy segregates to the surface, and the driving force for this partitioning was shown to arise even from very small differences in energetic effects. Detailed investigations of the predicted concentration profiles show that the segregation can be high enough to cause complete wetting of the surface by one of the components. In general, the extent of this segregation was found to depend strongly on the molecular weights, the energetic interactions with the surface, and the bulk volume fractions of the components in the melt. In addition, the inter facial tension was calculated in order to highlight some of the consequences of the segregation. Finally, calculations were performed to provide insight into the orientation of the chain segments and the behavior of chain ends in the interface. © 1991, American Chemical Society. All rights reserved.