Topology Matters: Conformation and Microscopic Dynamics of Ring Polymers

Abstract

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.

Elucidations of Structure and Molecular Dynamics of Complex Polymers by State-of-the-Art Solid-State NMR Spectroscopy

“…Especially, topological constraint is one of the unresolved topics in polymer crystallization. , Solid-state NMR is anticipated to provide more detailed information about the impacts of connectivity, flexibility, and topological constraint on polymer crystallization at the molecular level. , In polymer glasses, the dynamic heterogeneity, as related to spatial nanoscale heterogeneity or dynamic fluctuations, is an important driver for glass formation, while the quantitative characterization of such dynamic heterogeneity still remain elusive, not to mention its effects on macroscopic viscoelastic observations. , In polymer processing, the chain entanglements are dominating the flow behaviors of polymer melts, while quantitative characterization of the heterogeneous distribution of entanglements is still challenging . In polymer theory, direct molecular-level experimental evidence from ssNMR is expected to drive the development of theoretical models for polymers with special topologies, such as ring, star, bottlebrush, comb, etc., which are fundamentally important for the design of polymers with complex architecture and thus unique rheological and mechanical properties . In polymer applications, fundamental understanding of ion-containing polymers for better design of polymer electrolyte applications is still deficient due to the intricate interplay of charges transport, ionic correlations, compositions, self-assembled nanostructures, and chain dynamics .…”

Spin Relaxation and Dynamics of Ring Poly(ethylene oxide) in Melts

“…Although various properties of ring macromolecules started to be discussed several decades ago (see refs , and the literature cited therein), their systematic, experimental studies have begun relatively recently, and an understanding of their structural and dynamic properties still seems to be far from complete. − A fundamental and quantifiable property of ring macromolecules is the difference in their conformation in comparison to their linear analogues: The statistical distribution of conformations of linear macromolecules consisting of N Kuhn segments for sufficiently large N can be approximated with good accuracy as the distribution of a freely jointed ideal chain, and its gyration radius is equal to R g normall normali normaln = true( N 6 true) b , where b is the length of a Kuhn segment. − Ring macromolecules in a melt have a significantly more compact globular structure with a radius of gyration that, for large N , depends on N as R g ∝ bN 1/3 . This asymptotic behavior was found by numerical simulations, ,, but has never been verified experimentally. , The interaction between the intramolecular segments of macromolecules is equivalent to the interaction with segments of neighboring macromolecules. Therefore, the surface tension of globules formed by ring macromolecules is zero, and the globules do not have a distinct spatial shape.…”

Zwitterionic ring expansion polymerization of tert‐butyl glycidyl ether with B(C6F5)3 towards the generation of cyclic chains

“…This topology imparts distinct properties and behavior to cyclic polymers compared to their linear analogues, offering exciting opportunities for studying their structurefunction relationships. [1][2][3] In particular, water-soluble cyclic polymers are an important emerging area in biomedical research thanks to their proved higher chemical stability, prolonged blood circulation time and improved encapsulation efficiency compared to linear polymers. 2,[4][5][6][7] Zwitterionic ring expansion polymerization (ZREP) is a technique that allows the formation of cyclic polymers in one-pot reaction and large mass scales by making the right combination of monomer and catalyst.…”