AbstractWhen linear, conservative, molecular forces are used in this bead‐spring model of a polymer solution, a viscoplastic constitutive equation results. Using nonlinear intramolecular forces removes this viscoplasticity. The analysis shows that the anisotropy of the normal stresses is related to the anisotropy of the molecular forces. At the theta temperature the anisotropy of the intramolecular force alone determines the normal stress anisotropy. Nonlinear molecular forces are necessary for the analysis to predict a shear rate dependence for the stress in steady homogeneous flow. The symmetry of the stress tensor constrains the Hooke's law constants used to model the molecular forces. No overshoot is predicted for the stress response to a step change in shear rate when linear forces are used. Using linear forces, the stress response to a unit step shear rate shows a tendency of the polymer solution to undergo plastic deformation and to take a se
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