Thermodynamics of Polymer−Clay Nanocomposites Revisited: Compressible Self-Consistent Field Theory Modeling of Melt-Intercalated Organoclays

We formulate a “compressible” version of lattice self-consistent field theory (SCFT) to describe thermodynamic behavior of organically modified clays in polymer melt. The melt consists of the homopolymer matrix and a fraction of end-functionalized “active” chains, each chain having a single “sticker” end-group with strong affinity to the clay surface. We calculate the phase map for this system as a function of the melt composition and the strength of the “sticker” adhesion to the clay. It is shown that within the compressible SCFT model intercalated morphologies are favored in a significantly broader parameter range than was expected based on the incompressible SCFT analysis. We provide a qualitative analysis of this result and discuss implications for the physics of nanocomposites in general.