Dynamical simulation of structured colloidal particles
Hagy, Matthew Canby
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In this thesis, computer simulations are used to study the properties of new colloidal systems with structured interactions. These are pair interactions that include both attraction and repulsion. Structured colloids differ from conventional colloids in which the interactions between particles are either strictly attractive or strictly repulsive. It is anticipated that these novel interactions will give rise to new microscopic structure and dynamics and therefore new material properties. Three classes of structured interactions are considered: radially structured interactions with an energetic barrier to pair association, Janus surface patterns with two hemispheres of different surface charge, and striped surface patterns. New models are developed to capture the structured interactions of these novel colloid systems. Dynamical computer simulations of these models are performed to quantify the effects of structured interactions on colloid properties. The results show that structured interactions can lead to unexpected particle ordering and novel dynamics. For Janus and striped particles, the particle order can be captured with simpler isotropic coarse-grained models. This relates the static properties of these new colloids to conventional isotropically attractive colloids (e.g. depletion attracting colloids). In contrast, Janus and striped particles are found to have substantially slower dynamics than isotropically attractive colloids. This is explained by the observation of longer-duration reversible bonds between pairs of structured particles. Dynamical mapping methods are explored to relates the dynamics of these structured colloids to isotropically attractive colloids. These methods could also facilitate future nonequilibrium simulation of structured colloids with computationally efficient coarse-grained models.