Rheological Properties of Ring Polymers and Their Derivatives

Abstract

Ring polymers are one of the model polymers to understand the relationship between molecular architecture and the dynamics of polymers. This review summarizes the recent rheological studies on pure ring polymers, ring/linear polymer blends, and ring polymer derivatives. Pure ring polymers exhibit different linear and nonlinear rheological properties from linear polymers owing to the absence of chain ends. The presence of linear chains in ring polymers sensitively influences the rheological properties due to the occurrence of spontaneous intermolecular ring/linear threading. This effect becomes significant when a ring and linear chains are connected in a molecule for tadpole-shaped and dumbbell-shaped polymers.

Linear Viscoelastic Properties of Putative Cyclic Polymers Synthesized by Reversible Radical Recombination Polymerization (R3P)

“…Cyclic polymers stand out from other topologies by their lack of free ends, which are central to models of relaxation of entangled linear and branched polymers. − Models developed to describe the dynamics of cyclic polymers include the double-folded closed ring model, double-folded lattice animal (DFLA) model, , fractal loopy globule (FLG) model, decorated loop model, and the Rouse ring model . It has been known for more than 35 years that the viscoelastic behavior of cyclic polymers − is very different from that of their linear counterparts. However, establishing quantitative, reproducible linear viscoelastic properties of cyclic polymers has been limited by uncertain purity (particularly studies in the 1980s) and by the limited range of molecular weights available for highly pure cyclic polymers prepared using liquid chromatography at the critical condition (LCCC) − that, in principle, separates cyclic molecules from linear chains.…”

Viscoelastic properties of comb-shaped ring polystyrenes

“…Many studies have been conducted on the dynamics of linear and branched polymers [1][2][3][4][5], and their properties are well understood with tube models that assume entangled polymers. Ring polymers, which do not have chain ends, exhibit dynamics significantly different from those of linear and branched polymers with chain ends [6][7][8][9][10]. Specifically, while linear/branched polymers with sufficiently high molecular weights exhibit a wide plateau region in the relaxation modulus due to intermolecular entanglements, ring polymers exhibit a power-law type decay of the modulus [8,10], suggesting that the global dynamics of the ring chain are considerably different from those of entangled linear/branched polymers.…”

“…Ring polymers, which do not have chain ends, exhibit dynamics significantly different from those of linear and branched polymers with chain ends [6][7][8][9][10]. Specifically, while linear/branched polymers with sufficiently high molecular weights exhibit a wide plateau region in the relaxation modulus due to intermolecular entanglements, ring polymers exhibit a power-law type decay of the modulus [8,10], suggesting that the global dynamics of the ring chain are considerably different from those of entangled linear/branched polymers. Several molecular models have been proposed to describe the dynamics of ring polymers [11,12], but the dynamics are still not fully understood.…”

“…Tadpole-shaped polymers in which a single linear chain is connected to a ring exhibit characteristic viscoelastic properties [10,13,14]. That is, the linear chain part of the tadpole polymer spontaneously penetrates into the ring part of another molecule, resulting in significantly slower global relaxation than that seen for the individual ring polymer.…”