Cooling a material or increasing its density results into an increase of its viscosity by many orders of magnitude, bringing about an amorphous state that has the structure of a liquid and behaves macroscopically as a solid: this (metastable) state of matter is universally known as a glass. In conventional glass formers, particles are trapped in-between their neighbours, providing what is known as mutual caging, and leading to an enormous slowing down of individual (diffusive) and collective (coherent) dynamics simultaneously. Not so in concentrated solutions of ring polymers, as it was recently found by an international team around Univ.-Prof. Dr. Christos Likos – head of the group “Physics of Soft Condensed Matter”. Their work “Cluster Glasses of Semiflexible Ring Polymers” was selected for publication by ACS Macro Letters, a scientific journal of the American Chemical Society which was first published in 2012.

In their research, a novel type of glass has been discovered by extensive computer simulations. The ring polymers form extended clusters whose form and mutual spatial arrangement remains frozen in time, bringing about glassy collective dynamics. On the other hand, individual ring polymers incessantly hop between the clusters, giving the system a diffusive dynamics that decouples from the collective one and is akin to diffusion in usual, ergodic liquids. The work was featured on the cover of Volume 3, Issue 7 of the highly selective Journal "ACS Macro Letters”.

Original publication: “Cluster Glasses of Semiflexible Ring Polymers”, Mohammed Zakaria Slimani, Petra Bacova, Marco Bernabei, Arturo Narros, Christos N. Likos and Angel J. Moreno, ACS Macro Lett. vol. 3, issue 7, 611−616 (2014); dx.doi.org/10.1021/mz500117v