Structural relaxation time and rigidity of ordered suspensions of monodispersed polystyrene latex spheres studied by spectrophotometric and conductance stopped-flow techniques

Abstract

The structural relaxation time (τ) of the fast formation of the ordered suspension structure is directly observed by spectrophotometric and conductance stopped-flow techniques for deionized polystyrene latex spheres (85–2950 nm in diameter and 0.1–6 vol% in concentration). Two kinds of τ values, fast ( τ f) and slow, are observed, and the latter is assigned to the local fluctuation of the grain boundaries and/or crystallites themselves. The τ f values decrease with latex concentration. The translational diffusion constant of latex spheres in the lattice structure is evaluated from τ f and increases with latex concentration. The rigidity of the ordered crystallites obtained from τ f ranges from 0.1 to 2 dyn · cm −2 and increases as the concentration and the charge density of the spheres increase and the size of the spheres decreases. These results are consistent with the significant role of the electrical double layers under the influence of purely electrostatic repulsive forces in the effective hard sphere model.