ORDERING OF LATEX-PARTICLES AND IONIC POLYMERS IN SOLUTIONS

Experimental data that substantiate the intermacroion (or interparticle) attractive interaction were reviewed. In addition to the fact hitherto often emphasized by us that the observed spacing between solute species (2Dexp) is smaller than the average spacing (2D0) at low solute concentrations, the tendency of the 2Deip to decrease with decreasing dielectric constant of the solvent was pointed out to be consistent with the existence of an electrostatic attraction between latex particles: the 2Dexp should increase if only the repulsion is in action. The insensitivity of the 2D to temperature is suggested to be due to the intensification of the attraction caused by the corresponding change of the dielectric constant with temperature. The enhanced attraction counterbalanced the thermal expansion, resulting in insensitivity; according to the repulsion-only assumption widely believed, the spacing should increase with the decrease in dielectric constant and with the rise in temperature, which is contrary to the observation. The single broad scattering peak often observed for ionic polymers and latices was accounted for in terms of the paracrystalline distortion, the limited size of the localized ordering, and the Debye-Waller effect without invoking the repulsive interaction between the solute species. The kinetics of the growth of the localized ordered structures of polymer latices was studied in dilute suspensions. The growth of the structure was found to obey the Ostwald ripening mechanism: larger structures grew at the expense of smaller ones, which demonstrates that the surface tension of the structure is important and hence the attractive interaction between latex particles. Consistent with this idea, larger structures were found to live longer than smaller ones. © 1990, American Chemical Society. All rights reserved.