Layered Ceramics

Mica-type layered silicates can bear a natural negative charge because of the isomorphous substitution of silicon in octahedral sheets by aluminum or magnesium. The charge is generally balanced by potassium cations that reside in the galleries between layers. The intercalation of organic polymers between sheets of layered ceramics provides access to novel polymer-ceramic nanocomposites. These nanocomposites exhibit unique physical and mechanical properties attributable to the synergism of the individual components. The build-up of the multilayers in a stepwise manner rather than in the bulk "all-at-once" manner is of special interest. Kleinfeld and Ferguson [52] were first to apply the electrostatic layer-by-layer adsorption to produce multilayers of anionic synthetic silicate—hectorite and cationic PDDA. We used the polyion assembly to build up multilayers with alternating 1-nm-thick montmorillonite sheets and cationic PEI or PDDA [64-65]. The film thickness increase for the montmorillonite adsorption cycle was 1.1 nm and for PEI 2 nm. After 20 cycles, the resultant film had a permanent thickness of 63 nm.

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