Large amplitude oscillatory shear (LAOS) has been employed widely to probe the nonlinear behavior of complex fluids. Typically, the system undergoing LAOS has been assumed to experience homogeneous shear in each cycle so that material functions can be introduced to analyze the nonlinear dependence of these functions on the amplitude and frequency. Using particle-tracking velocimetric technique, we have carried a more systematic investigation on four different entangled polybutadiene (PBD) solutions with the number of entanglements per chain Z=13, 27, 64 and 119, extending well beyond the initial observations of shear banding in entangled PBD solutions under LAOS [Tapadia et al., Phys. Rev. Lett. 96, 196001–4 (2006a)]. At strain amplitudes γo>100% and frequencies higher than the overall chain relaxation rate, we observed, for the three samples with 27 or more entanglements per chain, the development of a thin “liquid” layer where severe chain disentanglement may have taken place. The thin liquid layer take...