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 (2Dexp) in the hexagonal ordered regions are smaller than the calculated average values for a face-centered-cubic distribution (2D0,h) at low polymer concentrations (0.2–2 vol %). However, at high concentrations, up to 12%, the 2Dexp value approaches 2D0,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.

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Publication costs assisted by the CUNY Faculty Research A ward ProgramGeneral expressions for the free energy of an arbitrary discrete electrostatic charge distribution in a prolate or oblate spheroidal cavity in a homogeneous polarizable dielectric continuum are derived and discussed. The derivation is checked by correspondence with expressions for special cases previously reported and by correspondence with the analogous expression for the spherical case as the cavity dimensions approach those of a sphere. The results are useful for elementary theoretical treatments of environmental effects on molecular structure and properties.

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