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A series of polyaniline-Fuller's Earth (PANI-FE) nanocomposites were prepared by the successive intercalation of anilinium ions followed by polymerisation within the interlayer spaces of Fuller's Earth (a type of calcium montmorillonite). The first member in the series is prepared by exchanging the calcium ions in Fuller's Earth for ammonium ions and subsequently for anilinium ions and polymerising the latter using an externally introduced oxidant. The emeraldine salt form of polyaniline formed is then neutralised with ammonium hydroxide and more anilinium ions are exchanged for ammonium ions and polymerised to get the second member. In this manner, by making use the unique chemistry of clay and polyniline, four members of PANI-FE are prepared. In the last member, the negative layer charges of Fuller's Earth is completely neutralised by the positive charges of the polymer. The extent of polymer loading in each stage, the effect polymer has on the host structure and the electronic and ionic components of the conductivities of the new PANI-FE nanocomposites are investigated. The Fe(III) sites in FE are capable of spontaneously polymerising aniline within its intergalleries. The extent of spontaneous polymerisation is limited by the amount of Fe(III) present in the FE. The deliberate polymerisation of remaining anilinium ions by externally introduced oxidant results in highly conductive emeraldine salt-FE (EMS-FE) nanocomposites. The FE host accommodates higher amount of emeraldine salt and the repetitive insertions of the polymer could be done four times for complete layer charge neutralisation whereas with Bentonite the layer charge saturation takes place with three successive insertions. The new EMS-FE nanocomposites exhibit more than order of magnitude greater tuneable ionic and electronic conductivities compared to those of the same polymer incorporated in Bentonite.

The importance of a number of techniques (including1H and13C NMR, XRD and IR) in exploring the important catalytic properties of synthetic and natural clays is described. A clear distinction is observed between proven catalytically-active clays (e.g. Al-exchanged) and those which are generally less effective (e.g. Na-exchanged).13C NMR spectroscopy is used to identify directly products formed within the interlayer regions, and temperature-controlled powder XRD serves as a useful tool for identifying whether or not intercalation occurs under variously defined conditions. High-pressure XRD is used to verify the formation of different products during reaction.

Direct 57Fe-Mossbauer-spectroscopic evidence is presented for the involvement of lattice-subsituted iron(III) as an electron-accepting site, within montmorillonite, following intercalation of the clay by benzidine which results in the production of benzidine radical cations. The subsequent oxidation of the resulting iron(II), by dehydration of the benzidine blue–montmorillonite intercalate, is explained in terms of two simple equilibria which are set up at the clay surfaces. New Lewis-acid sites [involving iron (III)], created by oxidation of the original (ironII) ions in the clay, have been found to be active even under conditions where it is expected that benzidine species are present only at external surfaces of the montmorillonite.

Aniline is produced in good (ca. 45%) yield when the intercalate of montmorillonite and 4,4′-diamino-trans-stilbene is heated, in vacuo, to ca. 300 °C.

Aniline is produced in good (ca. 45%) yield when the intercalate of montmorillonite and 4,4′-diamino-trans-stilbene is heated, in vacuo, to ca. 300 °C.

Clay minerals of the montmorillonite family provide a matrix on which radical cations of a variety of amines may be formed. The origin of the different colours associated with the benzidine (bzn)–. NNN′N′-tetramethylbenzidine (tbzn)–, and trans-4.4′-diaminostilbene (dsn)-montmorillonite complexes has been further elucidated by u.v. and visible reflectance and i.r. spectroscopy. It is established that both uni- and di-positive bzn radical cations and protonated bzn moieties can exist at the internal and external clay surfaces. This is in contrast to the situation which prevails for tbzn where only the unipositive radical cation and protonated moieties appear to be formed. The interaction of montmorillonite with dsn dihydrochloride is similar to that of bzn but the nature of the product is modified by the precence of protons in cation-exchange sites.

Various types of novel reactions (relevant in bio-organic, inorganic, and prebiological contexts) which can be effected within spaces between the layers, or at the surfaces, of sheet-silicate minerals are summarized. The colour reactions displayed by nine selected nitrogen-containing small aromatic molecules when they complex with montmorillonite are also briefly reviewed, together with the results of a quantitative adsorptive study of benzidine on this particular mineral. Concurrent measurement of Na+-ion release from, and uptake of benzidine by, the mineral, and X-ray measurements of interlayer spacings, clearly reveal pre- and post-intercalation stages of the formation of the complex.