Tube relaxation: A necessary concept in the dynamics of strained polymers

A theory for the relaxation of large strains in polymer melts is outlined. It is based on the Doi–Edwards slip‐link model and the new concept of tube relaxation. Self‐consistency makes this concept necessary when polymer melts are concerned. The discrepancy with previous non‐self‐consistent theories is not negligible and should be easy to observe experimentally. Special attention is given to the overall size and to the mean orientation of a labeled N‐chain in a step‐strained melt of P‐chains. Using semiquantitative arguments, we predict different regimes depending on the respective values of N and P, and propose approximate evolution equations for each case. These equations may be used to design and interpret a variety of fluorescence, infrared, or NMR polarization measurements, as well as small‐angle neutron scattering experiments.