The Shear Rheology of Semi-dilute Dna Solutions

Dilute polymer solutions and polymer melts in shear flow have been extensively studied experimentally and theoretically. However, a systematic experimental study to understand the influence of concentration, temperature and molecular weight on the rheology of semidilute polymer solutions is currently lacking. Such knowledge is of crucial importance in a number of industrial and biological contexts. In this work, the shear rheology of linear DNA molecules (which have near perfect monodispersity) has been investigated in a wide range of molecular weights (25 – 165.6 kilobasepairs), temperatures and concentrations. Steady state shear viscosities in semi-dilute regime have been determined. The dependence of the zero shear rate viscosity on concentration is observed to display universal behaviour that can be understood in the framework of scaling theories for polymer solutions. Further, the shear rate dependence of viscosity, at various temperatures, can be collapsed onto a master curve when interpreted in terms of a concentration dependent Weissenberg number. The current work will provide benchmark data that can be used for the validation of theoretical studies.