Clays are essentially composed of crystalline particles of one or more members of a small group of minerals. The ability of clays to intercalate certain organic substances has been known for a very long time. There is a scope in these clay structures for isomorphous replacement, that is, for substitution of Na+ by cations of similar size but usually of lower valency. This research aims at identifying suitable additives for pretreatment of clay and determining the effect of different classes of compounds (intercalants) on the d-spacing expansion of clay layers. This paper addresses a different approach to ion exchange for treatment of sodium montmorillonite, with different functional groups: aldehyde, ether, alcohol, glycol, and stearates. The results were compared with commercially available clays, Cloisite 25A and Cloisite 30B (Southern Clay Products), which are montmorillonite (MMT) clays intercalated with quaternary ammonium salts. The d-spacing increment in this research was consistent with the d-spacing achieved in commercially available clays. Future research will be to utilize the treated clay to produce polymer composites.