Intercalation complexes have been prepared from kaolinite and ammonium propionate in a stepwise procedure, by using hydrazine displaced by ammonium acetate in order to form a 14 A complex. At this stage the interlayer bonding energy drops to a minimum. Ammonium propionate intercalation complexes showing very sharp 001 reflections can then be obtained under well-specified hydration conditions.
Starting with a single complex, during a process of dehydration a series of complexes is produced which have d spacings ranging from 12-25A depending upon the state of hydration and the arrangement and particular species of ions among the clay layers. Characterization studies by infrared suggest the path of reaction which leads from one complex to another. The data from chemical analyses coupled with experimental results obtained from differential scanning calorimetry suggest the structural role of the water.
The several models proposed indicate that spacing transitions between the various complexes result from the formation of water bridges between ammonium propionate molecules, the anchoring to the internal OH layer being achieved by hydrogen bonding with the carboxyl group. The intercalated propionate solution may be considered as forming a quasi-liquid crystal organized within the kaolinite interlamellar space.