General trends in the structure and phase behaviour of polyelectrolyte-nanoparticle assemblies

Aqueous mixtures of oppositely charged polyelectrolytes (PE) and nanoparticles (NP) self-assemble into dense complexes. This self-assembly forms the basis of diverse phenomena ranging from flocculant action in water treatment, where the PE-NP flocs phase separate and sediment, to DNA compaction around histone proteins into chromatin. Factors such as the PE concentration, length, architecture and concentrations; NP charge, morphology and concentrations; and solution conditions (pH and ionic strength) play key roles in directing these PE-NP assemblies. In this presentation, we will delineate fundamental investigations into the phase behavior and structure of polyelectrolyte-NP assemblies using small angle X-ray scattering, turbidimetry and rheology with systematic variation of PE sizes and flexibility, NP sizes, and a wide range of concentrations of both components. Trends in interparticle spacings correlations as well as fractal dimensions of assemblies with varying PE and NP concentrations will be discussed, presenting a comprehensive narrative of the hierarchical structure of PE-NP self-assemblies. A general collapse of these trends on a master curve will be highlighted, providing universal guidelines for tailoring the microstructure of these assemblies.