Topological interactions in polymers under shear

Max Wolff
Max Wolff. Photo: Camilla Thulin.

The Swedish Research Council reached a decision on February 23, 2017 on project grants and starting grants on Natural and Engineering Sciences. The Department of Physics and Astronomy is granted 45.9 million SEK for the period 2016-2020 for in total six project grants and six starting grants. The projects will begin during 2017.

Project description

Max Wolff, Materials Physics, was granted 3.475 million SEK for the project “Topological interactions in polymers under shear” from the Swedish Research Council for the period 2017-2020.

Project description

Many polymers are complex liquids offering unique properties. One peculiarity of polymers is the pronounced non Newtonian behavior or in other words the change in viscosity for different shear rates. The distinctive changes in the shear and loss moduli can be explained by microscopic properties like the structure or internal relaxation of the molecules. However, experimental data on the changes in the local dynamics of polymers under shear load are scarce or even missing in our days. Even structural information for high molecular weight polymer melts is rare since the Weissenberg effect makes in-situ shear experiments very difficult. Still such information is essential to draw a complete picture of flow in polymers. Neutron scattering techniques are ideal to fill in this gap, since they combine a high sensitivity to light elements with the right time and length scales to probe the local structure and dynamics. The large penetration power for many engineering materials allows in-situ shear experiments. In this project, we will apply high resolution neutron spectroscopy to polymers under flow. The experiments will be complemented by small angle scattering experiments probing the microscopic structure. Our investigations will reveal phase transitions under shear and in particular trace a possible disentanglement of the polymer chains for higher shear rates.