Topological glass transition: from synthetic ring polymers to DNA


Topic  59
Main supervisor Margarita Kruteva (
MLZ institution FZJ
Local supervisor 1
Riccardo Brancaleon
Local supervisor 2 Martin Steinhart
University Osnabrück
Local supervisor 3
Local supervisor 4
Topological glass transition: from synthetic ring polymers to DNA
Other than for linear polymers, for rings interpenetration is costly entropically and compact structures that evolve for high molecular weight are induced. Consequently, the ring conformations are assumed to become mass fractals confining rings into territories. Nature exploits this phenomenon e.g. in packing chromatin rings consisting of DNA and proteins in nucleosomes providing thereby a very rapid access to genetic information. Finally, the unique properties arising from their cyclic topology render ring polymers promising candidates for some emerging applications, such as drug delivery, surface modification, and hierarchical assembly. (B. Golba et al. Biomaterials 2021; R. Lienard et al. J. Polym. Sci. 2020).
An intriguing aspect of ring polymer dynamics relates to a predicted topological glass transition, where the dynamical arrest does not occur on the level of the monomeric building blocks but on the scale of the chain size and beyond (J. Smrek et al. Nat. Commun. 2020). By pinning randomly a small ring fraction, simulations evidence for a transition to a kinetically arrested state, a phenomenon not observed for linear polymers. The arrested states are assumed to result from interring topological interactions or threadings.
Thus, while the monomeric building blocks stay mobile, large-scale fluctuations and in particular center of mass diffusion are slowed down and finally become arrested. The spontaneous transition to an arrested state is predicted to occur for very large rings. There the network of threadings become deeper and lead to the predicted arrest.
In this GNeuS project we plan to synthesize large hydrogenous and deuterated ring polymers to investigate the topological glass transition on the microscopic level. The kinetically arrested state will be modelled by pinning a fraction of a ring on inner solid surfaces of porous Alumina. The details of the microscopic dynamics will be investigated by neutron scattering methods and diffusion NMR.