Studying Structural Changes of Rod-like Nanoparticles Using Dynamic Light Scattering

The Zetasizer Nano is used to measure the size of a polyelectrolyte-surfactant complex at a range of pH values, which indicates a reversible change in complex structure at low pH. A series of novel polyelectrolyte-surfactant complexes were studied in order to probe several candidates as potential pH sensitive materials. At neutral pH, the complexes are water soluble, rod-like nanorods. However, gelation and longer-range interactions are observed as the pH is dropped to low values (approximately pH 1). This is proposed to be a change in the complex structure, and dynamic light scattering (DLS) is used to determine changes in the overall complex size in dilute solutions. Currently, since the shape is not known, the translational diffusion coefficient that is measured in DLS is used to calculate an effective hydrodynamic diameter of the complex. The hydrodynamic diameter is measured as the pH of the solution is reduced from neutral to acidic condition, ranging between 180nm down to 50nm hydordynamic diameter.

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