Linker-mediated interactions can provide statistical control of valence in colloidal networks; restricted average valence at low linker-to-colloid ratios produces phase behavior reminiscent of patchy particles and conducive to forming “equilibrium” gels [1]. Wertheim theory provides a framework that predicts phase behavior and bonding motifs of such linker-colloid mixtures [1,2]. However, it was recently demonstrated [3] that the most commonly used approximation, thermodynamic perturbation theory (TPT), overestimates the region of parameter space where phase separation spontaneously occurs. This overestimation is attributed to TPT’s neglect of one-colloid loops (self-links) and two-colloid loops (redundant links) that do not help extend the network. Here, we investigate a recently introduced modification of the theory (TPT+), which can account for these bonding motifs [4]. Specifically, we use the theory to explore how experimentally controllable parameters in a simple, coarse-grained linker-colloid model can be modified to produce phase behavior with accessible paths to “equilibrium” gel states. We test those predictions with computer simulations.

Wertheim theory predictions for phase behavior and bonding motifs of linker-mediated colloidal gel formers

ACS Spring 2022

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