Re-entrant dynamics in polymer-linked colloidal networks

Linked colloidal gels composed of functionalized building blocks and complementary linker molecules can form an equilibrium gel phase at low volume fractions. Here, we use computer simulations of a coarse-grained model to establish that polymer-linked colloidal networks show dynamic hallmarks of equilibrium colloidal gels with re-entrant behavior as a function of the linker-to-colloid ratio. The simulations reveal the link between colloidal structural relaxation and the decorrelation time of linker-mediated colloid-colloid bonds. The latter relates to the number of effective bonds per colloid, which varies nonmonotonically with linker concentration in a way that can be predicted from a thermodynamic perturbation theory which accounts for linker looping and redundant bonding motifs. Our results provide a basis for controlling macroscopic properties of the gel by tuning the linker-to-colloid ratio.