Saponite structural formulas

Chemical analyses and structural formulas of some saponites... 

Saponite is the trioctahedral equivalent of beidellite. Its structural formula is... 

These experiments do not prove, but suggest the existence of a qualitative boundary separating saponites from vermiculites. This boundary cannot be found in the structural formula. If it exists, it can only be found in the distribution (ordered and disordered) of isomorphous replacements. The exact structure of saponites is still poorly known. Vermiculites are most often derived from biotite and phlogopite and could inherit the structure of the tetrahedral layers of micas. The A1 atoms in the tetrahedral layers of micas form unidimensional, ordered ensembles (linear chains of substitution Gatineau [1964] and Gatineau and Merino [1966]). 

Montmorillonite, hectorite, and saponite are the most widely investigated clays. Their structure and formula are shown in Figure 9.1 and Table 9.1, respectively. Montmorillonite is a very popular choice for nanocomposites because of its small particle size (<2 pm) and hence the easy diffusion of polymer into the clay particles. They also have high aspect ratios (10-2000) and high swelling capacity, which are essential for efficient intercalation of the polymer. The physical mixture of a polymer and a clay may not form a nanocomposite. This situation is analogous to that in a polymer blend, and separation into discrete phases takes place in most cases. Pristine clay usually contains hydrated Na+ or K+ ions. Obviously,... 

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