Polymer compression in shear flow

Abstract

Polymers in flow deform elastically as a result of reduced entropy stored in the distorted chain. Elastic stretching of the chains in flow is assumed; however, measurement of the deformation of individual chains in concentrated solution in flow has largely eluded experiment. Several recent simulations have shown that the chains may compress in flow to elastically deform. Here, we show that polymer chains compress in simple shear flow, using time-resolved fluorescence to measure changes in fluorescence resonance energy transfer of a tagged polymer molecule. Time resolved measurements allow quantitative determination of changes in polymer chain dimensions, and are free from potential artifacts..