Deuterium nuclear magnetic resonance study of the nematic phase of vanadium pentoxide aqueous suspensions

This article describes deuterium NMR experiments on nematic single domains of vanadium pentoxide suspensions in D2O. Despite V2O5 volume fractions as low as 0.7%, the spectra are well-resolved quadrupolar doublets, characteri stic of a uniaxial symmetry. We show that a simple model for the behavior o f water in these suspensions accounts for the value of the splitting and fo r its concentration dependence. In this way, we obtain information on the i nteraction between water molecules and V2O5 colloidal ribbons. Then, the so lvent (D2O) is used as a probe to study the reorientation time of the nemat ic phase. We show that this technique is sensitive enough to distinguish be tween reorientation through a transient instability or through a homogeneou s rotation. In this latter case, we measure the characteristic time of reor ientation tau in a magnetic field, as a function of volume fraction and tem perature. We show a very strong temperature dependence of tau, which contra sts with the athermal phase diagram of this system.