Spatial Demixing of Ring and Chain Polymers in Pressure-Driven Flow

We
investigate mixtures of ring and linear polymers in solution
at various number ratios, ranging from pure chains to pure rings,
and at densities around the overlap concentration. In bulk and at
rest, we find a shrinking of both topologies with increasing polymer
content of the solution. At the same time, we observe an increase
in the solution viscosity with a concomitant reduction of the polymer
diffusivity. When exposing ring-chain mixtures of any composition
to a pressure-driven flow in a slit channel, we find that ring polymers
always migrate toward the center, whereas chains populate the regions
of high local shear close to the channel walls. Interestingly, in
a pure chain solution, this cross-stream migration toward the walls
is absent. This phenomenon could be used to iteratively separate chains
and rings at high mass throughput in simple microfluidic devices using
pressure-driven flows. Furthermore, we show how pressure-driven flow
can be used as a computationally efficient approach for determining
the shear viscosity of (complex) liquids.