Nematic colloidal suspensions of V₂O₅ in water—or Zocher phases revisited

Abstract

Vanadium pentoxide gels and sols, V₂O₅, nH₂O, exhibit a ribbon-like structure. 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 ≈0·12mol 1⁻¹. Classical threaded textures were observed in polarized light and small angle X-ray scattering patterns of oriented samples displayed a diffuse spot quite comparable to that of the Tobacco Mosaic Virus. For a sample of volume fraction φ ≈ 5 per cent, the V₂O₅ ribbons are separated by about 160 Å, so that the cross sectional area of the ribbons is about 1300 Ų, in agreement with previous estimations by electron microscopy.