Ring polymer solutions feature distinct rheological properties stemming from the unique forms of self-organization and mutual entanglements that have their roots on the circular topology of these macromolecules. Although quite a bit is known about melts of long and flexible ring polymers, the Physics of short minirings whose persistence length is comparable to their contour size is much less known. In addition, the role of electric charge along the rings' backbone is poorly understood to-date. In this talk, I will present recent results on the interplay between polymer topology and (tunable) electric charge: in the first instance, it will be shown that concentrated solutions of semiflexible ring-shaped polyelectrolytes form a particular kind of cluster glass, in which rheology can be tuned by the concentration and valency of the counterions, whereby multivalent counterions act as glue that stiffens the glass but monovalent counterions melt it [1]. In the second instance, we will consider ribbon-shapled rings and we will demonstrate that changing the pH of the solution leads to a local tuing of the twist/writhe balance along the backbone, resulting into the formation of charge-regulated coexsitence between writhe-rich and twist-rich domains along the polymer backbone [2].
References
[1] Roman Stano, Jan Smrek, and Christos N. Likos, Cluster formation in solutions of polyelectrolyte rings, ACS Nano 17, 21369 - 21382 (2023).
[2] Roman Stano, Christos N. Likos, Davide Michieletto, and Jan Smrek, Topology-controlled microphase separation and interconversion of twist and writhe domains in supecoiled annealed polyelectrolytes, Physical Review Letters 135, 048101 (2025).