The mesoscopic theory of the slow relaxation of linear macromolecules

The review is devoted to the description of the relaxation behaviour of very concentrated solutions or melts of linear polymers. A mesoscopic approach, which deals with the dynamics of a single macromolecule among others and is based on some statements of a general kind, is used. From a strictly phenomenological point of view, the mesoscopic approach is a microscopic macromolecular approach. It reveals the internal connection between phenomena and gives more details than the phenomenological approach. From a strictly microscopic point of view, it is a phenomenological one. It needs some mesoscopic parameters to be introduced and determined empirically. However, the mesoscopic approach permits us to explain the different phenomena of the dynamic behaviour of polymer melts - diffusion, neutron scattering, viscoelasticity, birefringence and others from a macromolecular point of view and without any specific hypotheses. The mesoscopic approach constitutes a phenomenological frame within which the results of investigations of behaviour of weakly-coupled macromolecules can be considered. The resultant picture of the thermal motion of a macromolecule in the system appears to be consistent with the common ideas about the localisation of a macromolecule: one can introduce an intermediate length which has the sense of a tube diameter and/or the length of a macromolecule between adjacent entanglements. In fact, it appears to be the most important parameter of the theory, as it was envisaged by Edwards and by de Gennes.