The presentation will discuss the essence of nonlinear rheology of entangled polymeric materials. By contrasting the prevailing viewpoint of the past with the emerging worldview, we will show why a new paradigm is required for further research in the field. In particular, it is necessary to emphasize the fact, well-known to Maxwell, that a viscoelastic material is solid like in its mechanical response when deformed on time scales much shorter than the Maxwell relaxation time. This means that such a material must yield, i.e., undergo a transition from elastic deformation to flow (irrecoverable deformation) upon a startup of external deformation. The central question to address is whether this yielding would lead to strain localization, i.e., inhomogeneous deformation, contrary to the textbook assumption of homogeneous deformation. Five years after the initial discoveries in Phys. Rev. Lett.,
96, 016001; 196001;
97, 187801 (2006), we have now a pretty good idea of what to expect and why entangled polymers (over 100 million tons consumed yearly worldwide) respond to large deformation in manners different from the textbook description. The new understanding could become a valuable guide in many practical polymer processing settings as pointed out in -Science China
53, 151 (2010). The following folks have worked or have been working on the subject: P. Tapadia (Ph.D., 2006), P. E. Boukany (Ph.D., 2008), S. Ravindranath (Ph.D., 2010), Yangyang Wang (Ph.D., 2010), Xin Li (Ph.D., 2011), Xiangyang Zhu (Ph.D. candidate), Shiwang Cheng (Ph.D. candidate), Hao Sun
(Ph.D. candidate), Gengxin Liu (Ph.D. candidate), and Panpan Lin (Ph.D. candidate).
