Dynamical simulation of electrostatic striped colloidal particles

MC Hagy and R Hernandez, JOURNAL OF CHEMICAL PHYSICS, 140, 034701 (2014).

DOI: 10.1063/1.4859855

The static and dynamic properties of striped colloidal particles are obtained using molecular dynamics computer simulations. Striped particles with n = 2 to n = 7 stripes of alternating electric charge are modeled at a high level of detail through a pointwise (PW) representation of the particle surface. We also consider the extent to which striped particles are similar to comparable isotropically attractive particles-such as depletion attracting colloids-by modeling striped particles with an isotropic pair interaction computed by coarse- graining (CG) over orientations at a pair level. Surprisingly, the CG models reproduce the static structure of the PW models for a range of volume fractions and interaction strengths consistent with the fluid region of the phase diagram for all n. As a corollary, different n-striped particle systems with comparable pair affinities (e.g., dimer equilibrium constant) have similar static structure. Stronger pair interactions lead to a collapsed structure in simulation as consistent with a glass-like phase. Different n-striped particle systems are found to have different phase boundaries and for certain n's no glass-like state is observed in any of our simulations. The CG model is found to have accelerated dynamics relative to the PW model for the same range of fluid conditions for which the models have identical static structure. This suggests striped electrostatic particles have slower dynamics than comparable isotropically attractive colloids. The slower dynamics result from a larger number of long-duration reversible bonds between pairs of striped particles than seen in isotropically attractive systems. We also found that higher n-striped particles systems generally have slower dynamics than lower n-striped systems with comparable pair affinities. (C) 2014 AIP Publishing LLC.

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