Interfacial Properties and Adsorption of Polymer−Solvent Binary Mixtures

Abstract

The phase behavior and interfacial properties of mixtures of chain molecules built of 2, 4, and 10 segments with monomeric species are studied using density functional theory. The chain molecules are modeled as fully flexible chains of tangentially bonded spherical segments. The chain segments and the solvent molecules interact via the truncated Lennard-Jones potential. Within density functional theory, we investigate the structure of the fluid−fluid interface and interfacial tension. In general we find an accumulation of the solvent particles at the interface. For mixtures with longer chains, we find the complete wetting transition at the gas−liquid interface upon approaching the triple point. We also report mean field density functional theory results for adsorption of tetramer−monomer mixtures in slit-like pores. We present density profiles, adsorption isotherms, and phase diagrams and discuss the effects of the model parameters on the capillary condensation. The main effect is that confinement gives rise to a substantial enrichment of tetramers, relative to bulk phases. However, the global phase diagrams for confined mixtures belong to the same class of phase behavior as those for bulk phases.