Microrheology of Semidilute and Entangled DNA-Poly(styrene sulfonate) Composites

Composites of synthetic and natural polyelectrolyte solutions offer promising opportunities for designing materials with enhanced properties. However, the microstructure of these materials, crucial for tuning their properties, remains poorly understood. Here, we study the microrheology of DNA-Poly(styrene sulfonate) (PSS) composites, focusing on how polymer composition and ionic conditions impact their mechanical and dynamic behavior across semidilute to entangled regimes. The combination of DNA and PSS induces multi-scale polymer relaxations that influence particle transport, suggesting a complex interplay between the flexible DNA and the semiflexible charged PSS chains. Our findings reveal a high level of tunability in the structure and dynamics of these composites with significant implications for applications in biological systems and materials design. These results also enhance our understanding of the universality of diffusive modes in mixed polyelectrolyte-biopolymer systems, extending previous works on DNA and PSS systems individually.