Molecular Scale Dynamics of Large Ring Polymers

Abstract

We present neutron scattering data on the structure and dynamics of melts from polyethylene oxide rings with molecular weights up to ten times the entanglement mass of the linear counterpart. The data reveal a very compact conformation displaying a structure approaching a mass fractal, as hypothesized by recent simulation work. The dynamics is characterized by a fast Rouse relaxation of subunits (loops) and a slower dynamics displaying a lattice animal-like loop displacement. The loop size is an intrinsic property of the ring architecture and is independent of molecular weight. This is the first experimental observation of the space-time evolution of segmental motion in ring polymers illustrating the dynamic consequences of their topology that is unique among all polymeric systems of any other known architecture.

Effects of precursor topology and synthesis under crowding conditions on the structure of single-chain polymer nanoparticles

“…After equilibration under these new conditions, simulations are further extended over several million time steps to accumulate configurations for statistical time-averages. 3 Results and discussion 24,42 , while the ring precursors exhibit a scaling exponent ν = 0.36, which suggests highly collapsed conformations and is consistent with the scaling exponents found for ring polymers in melts, where they adopt crumpled globular conformations [35][36][37] . We investigate the effect of crowding on the resulting topology and structure of SCNPs by analyzing their size and their shape by means of the radius of gyration and the asphericity.…”

“…Increasing the density of the solution leads to collapse from selfavoiding to Gaussian conformations only in the limit of fully disordered SCNPs 33 or linear chains 34 . In general, as a consequence of their molecular topology with permanent loops, SCNPs in crowded solutions adopt crumpled globular conformations similar to those found for melts of ring polymers [35][36][37] . This observation, confirmed by SANS experiments 33 , in SCNPs -a system showing structural analogies with IDPs but free of specific interactions -suggests the former general scenario for the contribution of purely steric crowding to the conformations of IDPs in vivo (cell environments with concentrations of 10-40 % 38 ).…”

Topological Interactions in Ring Polymers

“…This scaling has been found, both numerically (see Chapter 4 and [Halverson et al, 2011a]) and experimentally (see [Gooßen et al, 2014,Doi et al, 2015), to correctly describe the size of ring polymers in melt, or dense solutions, in the limit of large polymerisation M .…”

Effect of chain stiffness on the structure of single-chain polymer nanoparticles

“…As a consequence of their molecular architecture with permanent loops, SCNPs exhibit a peculiar collapse behaviour in concentrated solutions and melts. Instead of the Gaussian conformations displayed by linear chains, they adopt fractal or 'crumpled' globular conformations [31,32] resembling those found for melts of ring polymers or chromatin loops [32,33,34,35,36], suggesting this scenario for the effect of purely steric crowding on IDPs in cell environments.…”