Relating the Microscopic and Macroscopic Response of a Polymeric Fluid in a Shearing Flow

The microscopic and macroscopic response of a polymer solution in start-up shear flow was investigated using fluorescence microscopy of single molecules, bulk viscosity measurements, and Brownian dynamics simulations. An overshoot in viscosity was observed upon flow inception and understood via the observed molecular extension and by simulation findings. Increasing the polymer concentration up to six times the overlap concentration ( $C^{*}$) has no effect on the character of the dynamics of individual molecules.