NEMATIC COLLOIDAL SUSPENSIONS OF V2O5 IN WATER - OR ZOCHER PHASES REVISITED

Vanadium pentoxide gels and sols, V2O5, nH2O, exhibit a ribbon-like st ructure. They form colloidal suspensions (also called Zocher phases or 'tactophases') which are clearly shown here to present a homogeneous lyotropic nematic phase for concentrations larger than almost-equal-to 0.12 mol l-1. Classical threaded textures were observed in polarized light and small angle X-ray scattering patterns of oriented samples di splayed a diffuse spot quite comparable to that of the Tobacco Mosaic Virus. For a sample of volume fraction phi almost-equal-to 5 per cent, the V2O5 ribbons are separated by about 160 angstrom, so that the cro ss sectional area of the ribbons is about 1300 angstrom2, in agreement with previous estimations by electron microscopy.