Unexpected power-law stress relaxation of entangled ring polymers

Abstract

After many years of intense research, most aspects of the motion of entangled polymers have been understood. Long linear and branched polymers have a characteristic entanglement plateau and their stress relaxes by chain reptation or branch retraction, respectively. In both mechanisms, the presence of chain ends is essential. But how do entangled polymers without ends relax their stress? Using properly purified high-molar-mass ring polymers, we demonstrate that these materials exhibit self-similar dynamics, yielding a power-law stress relaxation. However, trace amounts of linear chains at a concentration almost two decades below their overlap cause an enhanced mechanical response. An entanglement plateau is recovered at higher concentrations of linear chains. These results constitute an important step towards solving an outstanding problem of polymer science and are useful for manipulating properties of materials ranging from DNA to polycarbonate. They also provide possible directions for tuning the rheology of entangled polymers.

Monte Carlo simulation of a single ring among linear chains: Structural and dynamic heterogeneity

“…Some viscosity studies suggested that N c for rings is smaller than that of linear polymers, 3,4,6 but simulation results argued that N c for rings would be about two to five times higher than that of linear chains, 15 or even much larger. 17 Moreover, by demonstrating the self-similar dynamics of purified high-molarmass ring polymers, Kapnistos et al 24 even questioned the existence of N c for ring polymers.…”

“…properties of ring polymers in the ring-linear blends. [24][25][26][27][28][29][30][31] Iyer et al 28 proposed a scaling model on the size of ring polymers in ring-linear blend and found that by gradually increasing the composition of linear chains, the ring molecules swell, with Flory's scaling exponent v increasing from 0.4 to 0.5 in the limit of infinite dilution for the rings. Using the BFM, Subramanian and Shanbhag 29,30 studied the dynamics of entangled ring polymers in ring-linear blends and found the self-diffusion coefficient and the primitive path length of ring polymers are more sensitive to volume fraction than that of linear chains.…”

A topologically driven glass in ring polymers

“…In contrast, ring polymers possess a closed contour, which leads to markedly different relaxation and diffusion mechanisms. Recently, there has been much improvement in the production of purified systems of rings (6)(7)(8), with the consequent result that more and more experimental puzzling evidence requires a deeper understanding of their motion in concentrated solutions and melts from a theoretical point of view.…”

“…On the other hand, numerical and experimental findings (5,6) suggest that rings exhibit strong intercoil correlations, which have proved difficult to address in simplified theoretical models (9)(10)(11)(12). Because of this, there have been many recent attempts to rigorously characterize these interchains' interactions (13)(14)(15)(16), although a precise definition and unambiguous identification of these "threadings" in concentrated solutions of rings remains elusive.…”

Synthesis of star‐shaped poly(n‐butyl acrylate) oligomers with coumarin end groups and their networks for a UV‐tunable viscoelastic material

“…[7][8][9][10][11][12][13][14][15] Recently, commendable achievements have been experienced with the control of polymer properties by mixing polymers with linear and nonlinear architectures. Particular examples are tuning of domain spacing, 16 micellar morphologies, 17 and viscoelasticity, 18 and preparation of miscible blends with a Additional Supporting Information may be found in the online version of this article. combination of inherently immiscible polymers.…”