Biosynthetic Polyelectrolyte Composites Exhibit Tunable Scale-Dependent Mechanics Governed by Entanglements

We engineer composites of biological DNA and synthetic sodium poly(styrenesulfonate) polymers with judiciously matched physical properties that interpenetrate to form miscible solutions spanning from semidilute to entangled regimes at varying DNA fractions w_DNA and ionic strengths I. The DNA entanglement concentration robustly dictates the crossover from semidilute to entangled dynamics for all compositions and ionic strengths of composites (w_DNA > 0). The effect of I emerges in the concentration dependence of viscosity, which transitions from polyelectrolyte scaling to good solvent scaling for neutral polymers as w_DNA and I increase. Conversely, the dynamics at shorter spatiotemporal scales follow θ-solvent scaling. Thus, combining biological and synthetic polyelectrolytes enables independent tuning of the polyelectrolyte fingerprint, entanglement concentration, and solvent interactions, which can be leveraged for engineering miscible polymer composites with greater dynamic range and responsiveness for applications from energy storage to drug delivery.