Structure and Formation of a Gel of Colloidal Disks

We have performed static scattering experiments on the gel state of a suspension of disk-shaped charged colloidal particles. The combination of static light scattering and small-angle x-ray scattering experiments probes more than three orders of magnitude in the scattering vector q. We observe that, after application of shear, the form factor develops nematic-Iike order. This order decays to random orientation in the gel state. This suggests that local reorientation of the disks leads to the gel state, as opposed to aggregation.