Rheology of entangled solutions of ring-linear DNA blends*

The rheological response of ring polymers remains poorly understood, and even small amounts of linear chains can have large effects on their behavior. In this work, we use monodisperse ring DNA polymers (45 kbp, 2.9 x 10⁷ g/mol) to investigate the importance of linear chains in the rheology of ring-linear blends. Linear viscoelastic measurements have been made on ring-linear DNA solutions at various concentrations with different linear chain ratios and the responses compared to those of linear λ DNA (48.5 kbp) solutions. Because of the linear threading effects, the blends have a significantly higher zero-shear rate viscosity and a much broader rubbery regime than that of the linear polymer. Furthermore, a linear ratio of 0.5 is a threshold at which the magnitude of the plateau modulus G_N⁰ tends towards that of the linear counterpart. However, independent of the linear content, the power law dependences of G_N⁰ on total concentration for the blends are the same as that of the linear solutions. We also find that the Cox-Merz rule holds for the linear-ring topology.