Phase behavior and rheology of sticky rod-like particles

We construct colloidal ``sticky'' rods from the semi-flexible filamentous fd virus and temperature-sensitive polymers poly(N-isopropylacrylamide) (PNIPAM). The phase diagram of fd-PNIPAM system becomes independent of ionic strength at high salt concentration and low temperature, i.e. the rods are sterically stabilized by the polymer. However, the network of sticky rods undergoes a sol-gel transition as the temperature is raised. The viscoelastic moduli of fd and fd-PNIPAM suspensions are compared as a function of temperature, and the effect of ionic strength on the gelling behavior of fd-PNIPAM solution is measured. For all fluidlike and solidlike samples, the frequency-dependant linear viscoelastic moduli can be scaled onto universal master curves.