Diffusion of Charged Macromoelcules under Strong Electric Repulsion

The complicity of diffusive motion of individual charged macromolecules under strong electrostatic interaction has been puzzling for decades. As an effort to explore the mystery, diffusion of polyelectrolyte molecules is investigated at single molecular level. By dual-color fluorescence correlation spectroscopy, the diffusion of different sodium polystyrene sulfonate (NaPSS) molecules is discriminated and their mutual correlation demonstrates the strong coupling of the diffusion of different molecules, leading to the abnormal diffusion of individual NaPSS molecules. After the proper correction of the correlation function, the self-diffusion of NaPSS demonstrates a two-stage feature – a fast and slow diffusion modes. The results have exposed a new species in the multiple diffusion modes in polyelectrolyte solution.