Laser light scattering study of a rigid-rod polyelectrolyte

Static light scattering (SLS), dynamic light scattering (DLS), and depolarized dynamic Light scattering (DDLS) were employed to study methanolic solutions of an intrinsically stiff rigid-rod polyelectrolyte consisting of a poly(p-phenylene) backbone with dodecyl side chains. The solutions of the rigid rod polymers exhibit polyelectrolyte-solution properties at low counterion concentrations of tetramethylammonium chloride (TMACl). At higher salt concentrations, the single polymer molecules and the aggregates coexist in solution. The amount of aggregates varies with the polymer concentration and the nature of the counterions. By combining SLS with DLS studies, a new way of characterizing the basic parameters (such as the weight average molecular weight and the radius of gyration of the single polymer chains and the aggregation number of the aggregates) of the rodlike polyelectrolyte polymer chains in the presence of the corresponding aggregates has been presented. DDLS studies allowed for elucidation of the aggregated structures.