On the static and dynamic scattering from linear and branched polyelectrolytes at various screening lengths.

Abstract

During the two last decades, branched polyelectrolytes have been thoroughly studied from theoretical and experimental standpoints. In this report, we attempt to compare the behaviour of highly branched polyelectrolytes to that of their linear counterparts at low ionic strength. As expected, the expansion behaviour of the branched materials is considerably less than of that of the corresponding linear chains. Surprisingly, in the former case (sphere-like behavior), the ratio of the radius of gyration to the hydrodynamic radius ρ=Rg/Rh shows an opposite behaviour as compared to the second one (rod-like behavior); indeed, contrary to the case of linear chains for which this ratio increases, that of branched homologous decreases as the ionic strength is lowered. Analyzis of the data, depicted in Kratky plots, reveals substantial discrepancies between the both polymeric structures. Moreover, at high ionic strength, one observes a rod-like structure that undergoes a transition to a disordered conformation which is not however that of a random coil, whereas, at low one, it appears that the two double- helix unfold and the loop strongly expands.