Network theory for polymer solutions in large amplitude oscillatory shear

A framework based on molecular entanglement kinetics is used to interpret the large amplitude oscillatory shear (LAOS) behavior of polyacrylamide and polystyrene solutions. A kinetic rate equation for the balance of entanglements is capable of reasonably predicting previously reported LAOS data for these solutions. Secondary shear stress versus shear rate loops were manifested in both solutions under severe conditions, and we attribute these to nonaffine deformation. While affine transient network theory predicts reasonable agreement with the Lodge-Meissner relation in LAOS, the polystyrene solution disobeys the relationship at shear strain amplitudes exceeding unity. We explain this departure from the Lodge-Meissner relation in LAOS with nonaffine network deformation.