Polymer conformations of semi-diluted solutions in elongational flow

Prof. Christian Wagner
Inst. f. Experimentalphysik, Universität des Saarlandes

Tiny amounts of polymers can alter the flow behaviour of simple liquids dramatically. The huge increase of resistance against pure elongational flow is macroscopically described by the elongational viscosity. It is a crucial parameter in many different industrial processes where contraction flows are generic. A pure elongational flow stretches the macromolecules at maximum. This leads to surprising effects like the suppression of the finite time singularity in droplet detachments and the formation of filaments with a pure elongational flow. We present different methods like birefringence or small angle spin echo neutron scattering to investigate the microscopic polymer dynamic on length scales ranging from the complete contour length down to single Kuhn segments and try to relate this with the macroscopic flow phenomena.