Interfacial colloidal rod dynamics: Coefficients, simulations, and analysis

Colloidal rod diffusion near a wall is modeled and simulated based on a constrained Stokesian dynamic model of chains-of-spheres. By modeling colloidal rods as chains-of-spheres, complete diffusion tensors are computed for colloidal rods in bulk media and near interfaces, including hydrodynamic interactions, translation-rotation coupling, and all diffusion modes in the particle and lab frames. Simulated trajectories based on the chain-of-spheres diffusion tensor are quantified in terms of typical experimental quantities such as mean squared positional and angular displacements as well as autocorrelation functions. Theoretical expressions are reported to predict measured average diffusivities as well as the crossover from short-time anisotropic translational diffusion along the rod's major axis to isotropic diffusion. Diffusion modes are quantified in terms of closed form empirical fits to model results to aid their use in interpretation and prediction of experiments involving colloidal rod diffusion in interfacial and confined systems.