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 s urrounding polymer melt, which contains a volume fraction of end-functional ized polymers. The functionalized polymers contain two reactive "stickers", one at each end of the chain, that are highly attracted to the surfaces. T he surfaces model clay crystallites, or sheets. Through the calculations, w e determine the free energy profiles as the surfaces are pried apart and th e polymer fills the gap. The free energy vs distance plots reveal a distinc tive minimum, even at very small volume fractions of the end-functionalized chains. Thus, the presence of these telechelic polymers promotes the forma tion of thermodynamically stable intercalated composites, where the polymer s enhance the separation between the silicate sheets. However, the telechel ic chains prohibit the creation of the more desirable exfoliated structures , where the sheets are uniformly dispersed throughout the polymer matrix. T he results provide guidelines for significantly enhancing the separation be tween the sheets, thus possibly making properties of the intercalated compo sites more like the exfoliated material.