A small-angle X-ray scattering study of the isotropic and nematic phases of V2O5 suspensions

We report. small-angle X-ray; scattering experiments performed in both the isotropic and nematic phases of aqueous V2O5 suspensions. We show that the scattering in the isotropic phase can be well described in the whole access ible q-range by only considering the form factor of non-interacting ribbons . We investigate the influence of concentration and pH on the dimensions of V2O5 ribbons and show that these parameters do not have any significant ef fect, as long as the system stays well within the chemical stability domain of the ribbons. We then show that nematic single domains display an anisot ropic small-angle scattering pattern, even at scattering vectors small comp ared to that at which a characteristic correlation peak is observed. This f eature is expected for a nematic phase, but. was rarely observed. We finall y try to describe this scattering within the framework of theories develope d fur the structure factor of a nematic polymer, and we reach the conclusio n that chain ends are certainly important to understand this pattern.