Organo-Clay Complexes

Abstract

IT has been shown by X-ray analysis that certain organic compounds are taken up between the basal surfaces of montmorillonite and halloysite to form interlamellar complexes. The space occupied by the organic molecules is determined by subtracting the van der Waals thickness of individual clay sheets from the observed (001) spacing, and is normally less than that calculated by assuming that the molecules lie as flat as possible and also make van der Waals contact with the surface atoms of the clay. The apparent reduction in thickness has been ascribed to CH … O bonds^1–3 between the oxygen atoms of the clay surface, which have an induced negative charge arising from the isomorphous replacement charge, and the organic molecules. Polyvinyl alcohol, the crysta structure of which has been determined, appears to form a two-layer complex with montmorillonite in which there is van der Waals contact between the —CH₂ groups and the surface oxygen atoms, and the plane of the carbon chains is perpendicular to the (001) planes (unpublished work). This suggested that the orientation of the simple alcohols might be such that the plane of the carbon chain is perpendicular to the (001) plane, and not parallel as originally assumed^1,2,4. The most recent evidence is also against the latter assumption⁵.