Phase behavior and rheology of sticky rod-like particles

TL;DR

This study investigates the phase behavior and rheological properties of sticky, rod-like colloidal particles made from fd virus and temperature-sensitive polymers, revealing temperature-induced gelation and universal viscoelastic scaling.

Contribution

It introduces a system of semi-flexible, sticky rods with tunable phase behavior and demonstrates universal viscoelastic scaling laws across different conditions.

Findings

Phase diagram becomes independent of ionic strength at high salt and low temperature.

Network undergoes sol-gel transition with increasing temperature.

Viscoelastic moduli scale onto universal master curves.

Abstract

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.