X-ray and Raman scattering studies of the MSE (p-dimethylaminobenzenesulfonate) solid-state transformation

Groupe Matière Condensée et Matériaux, UMR CNRS 6626, Université de Rennes 1 Bât. 11A, Campus de Beaulieu, 35042 Rennes cedex, France

Received: 27 September 1999
Accepted: 20 September 2000

Abstract

A methyl p-dimethylaminobenzenesulfonate (MSE) single crystal is converted to the zwitterionic product p-trimethylammoniumbenzenesulfonate (ZWT) by an intermolecular methyl transfer reaction. We investigate the evolution of this thermally induced transformation in the solid state and the lattice instability which takes place at about 60% conversion by X-ray diffraction with the precession method and Raman scattering. For times before the structural change measurements give evidence of growth of long ZWT chains in a monoclinic matrix which progressively but weakly distorts. After the lattice instability at which ZWT molecules rearrange to an orthorhombic antiferroelectric array, one observes coexistence of monoclinic and orthorhombic domains in the mixed MSE-ZWT crystal. Both MSE and ZWT molecules are present in monoclinic and orthorhombic domains.