Nanomaterials: How to separate linear and ring-shaped molecules

Physicists have developed a reliable strategy to separate chemically identical macromolecules that differ only in their shape. What is the difference between linear chains and rings composed of the same material? The molecular building blocks are identical, but from a mathematical point of view the two structures have distinct topologies, namely ring and linear chain. This difference is readily recognizable on a macroscopic scale, as for example a golden ring and a gold bar, but represents a tricky task on the microscopic scale. The physicists Lisa Weiss and Christos Likos of the University of Vienna and Arash Nikoubashman of the Johannes-Gutenberg University of Mainz investigated strategies to separate nanoand microparticles of distinct topology. Their results are published in the high-impact journal ACS Macro Letters. The purely mathematical property - linear or circular - can have severe consequences in the world of materials. Since circular molecules lack any ends, which could serve as a starting point for degradation, they are more resistant and less entangled.