Abstract
The small-angle X-ray scattering on dilute solutions of ionic polymers (such as synthetic polymers, proteins, polynucleotides, surfactant micelles, virus particles) shows a single, broad peak. The peak position depends on the molecular weight of polymer. When two fractions of different molecular weights are mixed, there appears one peak at position different from and inbetween the original peak positions of the mother fractions. This suggests positively that "ordering" which is responsible for the scattering peak, is not intra-, but inter-molecular. Thus, the ionic polymers are concluded to be distributed in a fairly regular way. The interparticle distance (2Dexp) estimated by the Bragg equation is found to be smaller than the theoretical distance (2Do) calculated from the polymer concentration, suggesting the presence of a Coulombic interparticle attraction. These experimental findings are confirmed by using Polymer latex particles of larger dimensions (diameter 1000-4000 Å). The ordering formation of the particles in dilute solutions and the vibrational motion of the particles in the ordered array are studied by a light microscope. The thermal motion of these particles is violent even in relatively high concentrations. Finally, the DLVO theory is critically discussed; when an imperfection of the theory is corrected, a Coulombic interparticle attraction is demonstrated to exist, as was found experimentally.
