New Collaboration Combines Experiments & Simulation to Reveal Dynamic Topology of Polymer Blends
In July of 2019, when we could still travel, I was invited to attended a great workshop on Capri, off the coast of Naples, Italy. It was a fantastic meeting on the physics of polymers undergoing fast flows. While I was there, I met Qian Huang, Wendi Wang, and Ole Hassager and we began a collaboration combining their rheological experiments with my nonequilibrium molecular dynamics simulations to better understand "architectural polymer composites." These systems combine polymers of different architectures that topologically entangle in unique ways and produce new emergent fluid properties.
We added some ring polymers into a matrix of linear polymers. The linear chains thread through the rings, "sewing" them into the entangled matrix of linear polymers. When the fluid is elongated, these transient threadings force the embedded rings to elongate affinely, producing a large increase in the stress and viscosity. However, at large strains the linear chains unthread from the rings. With their "stitches" released, the ring polymers violently recoil and producing a sharp drop in viscosity.
This transient unthreading dynamics is a neat example of an emergent phenomena in the composite that has no analog in either pure component. It can also be harnessed to tune the nonlinear rheology of polymer liquids to make them more easily processed and controlled during manufacturing.
More details can be found here: