Viscoelastic properties of entangled polymers: The transient network model

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Abstract
The 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(α‐methylstyrene), poly(vinyl acetate) and polybutadiene.