The rheology of colloidal suspensions measured as rod-shaped particles emerge and grow

Colloidal rods can significantly alter the rheological properties of suspensions even at low volume fractions due to their anisotropic shape. Understanding the effects of rod volume fraction and anisotropy is necessary for tailoring the rheological properties of suspensions and gels. Many studies have explored the rheology of colloidal rod suspensions, but how the properties of a suspension varies with time as rods form and grow has not been explored. Here, we use bulk rheology to measure the viscoelastic properties of a suspension of polyamide colloidal rods as the rod-shaped particles emerge from a homogeneous surfactant and polyamide solution. By controlling the temperature of the system on our rheometer, we can tune the aspect ratio of the colloidal rods which form. We complement our bulk rheology measurements with microrheology performed using differential dynamic microscopy (DDM). With DDM we find the characteristic timescales of density fluctuations and can determine a confinement length scale for non-ergodic systems. Our work offers new routes for characterizing the rheological properties of colloidal rods and for probing how rods form in a model colloidal system.