Interlayer exchanged ion

Two fimdamental aspects of the organoclay determine the formation of epoxy nanocomposites from in-situ polymerization the abUity of the interlayer exchanged ion to act as a compatibUizer and render the layered silicate epoxyphilic , and the catalyzing effect of the exchanged ion on the polymerization reaction in the galleries [31]. 

The CEC of clay minerals is partly the result of adsorption in the interlayer space between repeating layer units. This effect is greatest in the three-layer clays. In the case of montmorillonite, the interlayer space can expand to accommodate a variety of cations and water. This causes montmorillonite to have a very high CEC and to swell when wetted. This process is reversible the removal of the water molecules causes these clays to contract. In illite, some exchangeable potassium is present in the interlayer space. Because the interlayer potassium ions are rather tightly held, the CEC of this illite is similar to that of kaolinite, which has no interlayer space. Chlorite s CEC is similar to that of kaolinite and illite because the brucite layer restricts adsorption between the three-layer sandwiches. 

Experiments by Mackenzie (1963) indicate that at temperatures above 300°C, 1 atmosphere, some expandable structures selectively retain certain ionic species which become non-exchangeable. Further it is known that aluminum hydroxides can fill interlayer sites as non-exchangeable ions (Coulter, 1969). Fixing of non-exchangeable ions is not part of the normal montmorillonite "behavior" and we will exclude such material from this mineral category. 

Ca and Mg is inversed for vermiculite and montmorillonite (Levy and Shainberg, 1972). Further, the natural mica-beidellite interlayered minerals (rectorite) are sodi-calcic while the mica-montmorillonite minerals (allevardite) are sodi-potassic. Quite possibly, the site of charge imbalance changes the selectivity coefficients for exchangeable ions. The montmorillonite series of interlayering will produce illite and the beidel-litic series could lead to a paragonitic or possibly calcic mica. 

M"+-TSM). The basal spacing of M" -TSM has been determined to be 9.6 A regardless of the interlayer metal ion M"". The metal ion-exchanged forms of the other layer lattice silicates were prepared in the same manner. 

The difference in chemical composition between kaolinite and illite is to be seen in the relatively greater degree of isomorphous replacement for illite. Furthermore, the positive charge deficiency is balanced by interlayer K+ ions. These ions are not available for ion exchange, while those exposed on the surface can be exchanged for other ions [13]. 

The method for preparing an alumina-pillared clay is shown in Figure 3.3. Interlayer Na+ ions in the original clay are exchanged with aluminium hydroxy cluster cations. When this material is calcined at between 300 and 500 °C, the cations become oxide pillars and release protons into the structure. An acidic and porous clay with a surface area of 200-500 m2 g-1 is thus formed. 

Fig. 3 Unmodified layered silicate left) and layered silicate with interlayer-exchanged alkyl amine ions (right) [151]...

Montmorillonite (MMT) is natural candidate for formation of nanocomposite due to special lamellar structure. In particular, the absorbed cation in interlayer provides ions exchange ability for intercalation of positive charged aniline monomer in the acid solution. Several approaches have been proposed to attempt to obtain ER active material based on PANI-intercalated MMT (PANI-MMT) nanocomposite [94-96]. Kim et al. [94] have introduced for the first time a kind of PANI-MMT (PANI-Na -MMT) nanocomposites as ER material. PANI-Na -MMT nanocomposite particles have been synthesized via emulsion polymerization. In the preparation, Dodecylbenzenesulfonic acid (DBSA) is used to disperse aniline monomer in xylene and then the clay colloid is added to form emulsion. 

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