Attraction between Surfaces in a Polymer Melt Containing Telechelic Chains: Guidelines for Controlling the Surface Separation in Intercalated Polymer−Clay Composites

Using numerical and analytical self-consistent field (SCF) calculations, we investigate the interactions between two closely spaced surfaces and the surrounding polymer melt, which contains a volume fraction of end-functionalized polymers. The functionalized polymers contain two reactive “stickers”, one at each end of the chain, that are highly attracted to the surfaces. The surfaces model clay crystallites, or sheets. Through the calculations, we determine the free energy profiles as the surfaces are pried apart and the polymer fills the gap. The free energy vs distance plots reveal a distinctive minimum, even at very small volume fractions of the end-functionalized chains. Thus, the presence of these telechelic polymers promotes the formation of thermodynamically stable intercalated composites, where the polymers enhance the separation between the silicate sheets. However, the telechelic chains prohibit the creation of the more desirable exfoliated structures, where the sheets are uniformly dispersed throughout the polymer matrix. The results provide guidelines for significantly enhancing the separation between the sheets, thus possibly making properties of the intercalated composites more like the exfoliated material.