Viscoelasticity of concentrated isotropic solutions of semiflexible polymers. 3. Nonlinear rheology

Nonlinear rheological properties of a tightly-entangled solution of persist ent macromolecules are calculated within the context of a tube model. It is shown that the curvature stress in highly deformed solutions of such chain s is dominated by the contributions of deformation-induced "hairpins", i.e. , rare but very tightly curved segments of the deformed chain conformations . The model is found to exhibit strain softening in shear deformations.