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AbstractWe use the dynamic light scattering technique (DLS) to study the dynamic behavior of complex constituted by weakly charged microemulsion in the presence of polyelectrolyte. We investigated the impact of adding oppositely charged polyacid (PAA), which is a pH-dependent polyelectrolyte, on the dynamics of charged microemulsion nanodroplets in an acidic medium at pH = 4.5 when the polyacrylic acid are partially charged. In a diluted regime, two diffusive relaxation modes are seen when adding (upon addition) the polyacrylic acid PAA to the microemulsion nanodroplets due to collective diffusion and self-diffusion fluctuations. In the concentrated regime, we observed three diffusive relaxation modes when charged microemulsion nanodroplets complexed with oppositely charged polyacrylic acid. We attribute the two first relaxation modes to the collective diffusion (fluctuation of concentration) and self-diffusion of the microemulsion nanodroplets. The third mode which is a slower relaxation mode; we attribute this relaxation process to the motion of the network formed by the polyacid PAA and microemulsion nanodroplets, or “breathing mode” of the network. [ABSTRACT FROM AUTHOR]