Angular Dependence in Static and Dynamic Light Scattering from Randomly Branched Systems

The static and dynamic properties of three randomly branched systems under good solvent conditions have been investigated by light scattering. Despite large differences in the topology and chemical structure of these systems one common scaled particle scattering function (P(qR g)) is obtained for the probed q range. In dynamic light scattering, however, the topological differences have a significant effect. At high q values the first cumulant Γ(q) exhibits a q 2.8 dependence for the systems with small repeating units and a q 3 dependence for the system with the largest repeating unit. These dependencies indicate internal motions with strong hydrodynamic interactions (Zimm-like behavior). The absolute values of the reduced cumulant Γ*(q) ≡ Γ(q)ηo/(q 3 kT) at high q values proved to be a sensitive measure of the internal mobility, and information on the internal structure of polymers can be deduced from these values. By comparison of the Γ*(q) values from the branched systems with those from linear systems under ϑ and good solvent conditions the nature of the local dynamics in the various systems is classified: for the system with the largest repeating unit the local dynamics of linear sections of the clusters are registered, whereas for the systems with smaller repeating unit, i.e. higher branching density, the local dynamics of branched sections are probed.