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A mineral liquid crystal orients under magnetic field : prospects of applications

Patrick Davidson (July 1998)

While thousands examples of organic liquid crystals may today be found, far fewer examples exist of liquid crystals of mineral origin. Physicists and chemists of the CNRS and of the University Paris 6 have shown that aqueous solutions (fluids or gels) of vanadium oxide V2O5) ribbons, though discovered more than a century ago, constitute one of the very rare examples of mineral liquid crystals. This common compound is already used, in the form of thin films, as anti-static layer in the photography industry, as electrochrome film for display devices, or as cathode for lithium batteries. Its synthesis can be obtained using a recent soft chemistry technique, that is to say with a low cost manner : polymerising in water and at ambient temperature. Exploiting the particular characteristics of these liquid crystal suspensions (anisotropy and fluidity), the researchers were able to align the V2O5 ribbons thanks to a moderate magnetic field. The quality of thin films deposited from these suspensions should thus be improved by maintaining the magnetic field during the film drying, opening by this way the road to the fabrication of new materials with novel properties. Applications may be envisioned, with low cost, in the field of molecular electronics, optical communications, composite materials and display.

Texture of a V2O5 ribbons nematic suspension, observed by optical microscopy in polarised light. The latter provides information about the local ribbons orientation within the suspension. The arrows indicate defects perturbing the ribbons orientation.

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