Smectic montmorillonite clay was modified via cation exchange with ammonium salts of poly(oxypropylene)-polyamines (400, 3000, and 5000 M-w). Unusually wide silicate basal spacing (up to 80 Angstrom) and high organic contents (up to 75 wt %) were observed when a 5000 M-w amine was used as the intercalating agent. Moreover, intercalation of the amines not only contributes to the widening of the silicate interlayer but also alters its organophilic nature. After intercalation of appropriate amine, the modified clays were highly dispersible in organic solvents and capable of lowering the interfacial surface tension of a toluene/water mixture. These properties were correlated to the amine conformational changes within the silicate gallery.