Viscoelastic properties of entangled polymers: The transient network model

Abstract

A new transient network model for associative polymer networksThe viscoelastic behavior of entangled polymers is modeled by a three-dimensional transient network where the entangled points are considered to act as temporary crosslinks. Polymer chains are represented by beads and springs. The effects of entanglements on chain dynamics are introduced by assigning enhanced frictional coefficients to selected beads as well as extra elastic couplings between pairs of the entangled beads. The formation and disengagement of the entanglements can be envisioned to be in a dynamic equilibrium. The strength of elastic coupling is set to decrease with increasing distance between the entangled points. The resulting modified Rouse-Bueche-Zimm matrix is solved for the relaxation times from which the dynamic moduli, relaxation moduli, steady-state shear compliance, and zero-shear viscosity are computed. Results are in excellent agreement with experimental data on monodisperse polystyrene, poly(a-methylstyrene), poly(vinyl acetate) and polybutadiene.

Viscoelastic Properties of Entangled Polymer. IV. Binary Blends of Monodisperse Homopolymers

“…Throughout the calculations , the enhanced frictional coefficient is assumed to have the high-friction-3 inside distribution , i.e., entangled beads near the chain middle have higher frictional coefficients than the ones at the chain ends . This type of distribution is not only intuitively reasonable , but also has been found to fit the experimental data very well for monodisperse polymers (12).…”

“…In this work , we shall apply the transient network model (12) to binary blends by incorporating the effect of the coexisting components on chain dynamics. We are then able to obtain the modified relaxation times for each component.…”

“…The fourth term on the right-hand side of Eq. 2 accounts for the elastic coupling forces acting between all pairs of N e entangled beads (12). They are inversely proportional to the interbead distance as shown in Eq .…”

Physics of actin networks. I. Rheology of semi-dilute F-actin

“…Finally, neither the possibility of electrostatic interactions between the filaments, which could create temporary cross-linkages, nor the possibility of filament breakage has been taken into account, in part because the effect of these phenomena on the mechanical spectra is incompletely understood. The possibility of temporary or reversible cross-linkages has been suggested as an explanation of some of the available rheologic data for actin gels (Nossal, 1988;Wachsstock et al, 1994), and a number of models have been applied to the understanding of reversibly cross-linked synthetic polymer systems (Hong et al, 1977;Edwards, 1986).…”