Ordered structure in dilute solutions of highly charged polymer lattices as studied by microscopy. I. Interparticle distance as a function of latex concentration

Abstract

The coexistence of ordered and disordered regions has been observed in dilute solutions of highly charged monodisperse latex particles, a copolymer of styrene and styrenesulfonate, by using a metallurgical microscope. Unlike latex particles of low charge numbers, the interparticle distances (2D_exp) in the hexagonal ordered regions are smaller than the calculated average values for a face‐centered‐cubic distribution (2D_0,h) at low polymer concentrations (0.2–2 vol %). However, at high concentrations, up to 12%, the 2D_exp value approaches 2D_0,h. The results are consistent with a ‘‘two‐state structure’’ containing ordered and disordered regions and indicate the existence of ‘‘attractive’’ interactions between the charged solutes. The findings are also consistent with those for other species of high charge densities such as synthetic macroions and simple ions.