Montmorillonite-Polyalcohol Complexes

Abstract
Some montmorillonites may be differentiated by complexing them with polyalcohols having a CH2 group that is not connected to an oxygen atom. Montmorillonites with a low layer charge and high valence interlayer cations have larger basal spacings for their complexes than do those with a high layer charge and low valence interlayer cations. The basal spacings of these complexes are relatively larger if the clay has a large initial water content. The spacings for some complexes which are initially equilibrated at very low humidities are small, indicative of little penetration by polyalcohol molecules. Polyalcohol molecules may have difficulty replacing water molecules that are associated with the interlayer cations. The spacings of complexes with ethylene glycol and glycerol do not depend upon the initial interlayer water content. Water molecules may be an essential component of mont-morillonite-polyalcohol complexes.The polyalcohol molecules probably are associated with the clay surface through weak C-H···O interactions although virtually no shortening of this bond distance occurs. The C-H···O interaction is enhanced by the presence of higher valence interlayer cations. OH groups increase the thermal stability of complexes probably by interacting with the exchangeable cations. Longer chain molecules are held more tightly between the silicate sheets. One layer of polyalcohol molecules between silicate sheets is more stable than two layers. One layer of organic molecules is more stable with higher valence interlayer cations. Small molecules such as those of ethylene glycol may pack down somewhat into the “hexagonal holes” in the silicate surface.