Entropic Freezing of Diffusion of Macromolecules at Intermediate Confinements

Our recent discovery [1-3] of the non-diffusive Topologically Frustrated Dynamical State (TFDS) in polymer dynamics will be annotated with its essential features. It is well known that the Zimm-Rouse (Ogston) model, entropic barrier model, and reptation model, respectively, adequately describe the diffusion of macromolecules as the degree of confinement by their environment is progressively increased. As a remarkable departure, for intermediate degrees of confinement preceding the entangled regime, macromolecules do not diffuse even though the experimental conditions are at room temperature, which is a drastic deviation from the Einstein law of diffusion valid at all non-zero temperatures. The origin of TFDS is attributed to extreme metastability arising from cooperative action of multiple deep entropic traps on a single confined macromolecule. We will discuss the magnitude of the extreme metastability in terms of its effective entropic barrier preventing its diffusion, transition from TFDS into entanglement regime, and implications of the TFDS.