Raman spectroscopic study of organo-montmorillonites

Abstract

A Raman spectroscopic study on the organo-montmorillonites prepared at different concentrations has provided a detailed observation about the ordering conformation of HDTMA+ ions confined within the montmorillonite interlayer. The ordering conformation shows strong dependence on the concentration of the confined amine. Both wavenumber and band width of antisymmetric and symmetric stretching modes are sensitive to the ordering conformation of the inserted organic cation. Furthermore, the wavenumber of the antisymmetric stretching mode is more sensitive to the mobility of the tail of amine chain than that of symmetric stretching mode does.
At room temperature, the conformational ordering is more easily to be effected by the packing density in the lateral model than in the paraffin-type model. However, at liquid nitrogen temperature, both the positions of antisymmetric and symmetric stretching modes are independent of the amine concentration, and the band width of symmetric stretching mode is sensitive to the ordering conformation of organic. Upon heating the organo-montmorillonites, both the position of the antisymmetric and symmetric stretching bands shift to higher wavenumbers, indicating the decrease of conformational ordering.