An extension of the Curtiss-Bird theory for the rheological properties of concentrated polymer solutions and melts

The constitutive equation for the elastic reptating rope model is considered in the limit at which the rope becomes inextensible. It is shown that in this limit a constitutive equation is obtained which differs essentially from the Curtiss-Bird theory if the correlation length is much smaller than the contour length of the rope. This constitutive equation contains an extra term related to correlations between segments. The differences between this result and the Curtiss-Bird theory are considered, and consequences are indicated.