Topology Matters: Conformation and Microscopic Dynamics of Ring Polymers

Ring polymers have fascinated theorists, simulators, and experimentalists as they are the simplest polymer without ends, giving rise to important topology related properties. We present the state of the art of recent synthetic efforts and investigations into the structure and dynamics of dense nonconcatenated ring polymer systems. Analyzing the existing knowledge, we identify challenges for future research: In the realm of synthesis the creation of well-defined high molecular weight rings based on different monomers are highly desirable. In the field of ring conformations, the existence of double folded structures that are at the basis of many theoretical approaches was severely challenged and further scrutiny is needed. Similarly, the issue of the size dependent transition to mass fractal structures, or the effect of local stiffness on the conformation and dynamics are open questions. The role of ring-ring threading in the terminal dynamics of rings needs to be further elucidated. In particular, the novel proposed topological glass transition for very high molecular weight ring melts awaits experimental verification. Experimentally, ring-linear blends are very seldomly investigated: only a small number of studies on the miscibility and the conformation of rings in such blends are available. Microscopic experiments on the dynamics are nearly entirely missing. Finally, as different theoretical approaches are always backed by corresponding simulations, a crucial task would be to find out how the different approaches connect to each other and which experiments should be performed.