Rheothermodynamics of the Doi-Edwards reptation model.

ABSTRACT

The Doi-Edwards reptation model is found to be thermodynamically consistent, both in the Independent Alignment Approximation and in its full formulation including the effect of tube extension. In the latter case, a new expression for the stress tensor is uncovered. Both the stress and the birefringence tensors after a step shear gamma obey the Lodge-Meissner relation; when gamma>>1 the shear stress at t=0(+) is proportional to gamma(-1)lngamma, the first normal stress is proportional, lngamma and both the stress-optical law and the time-strain factorability are violated. A principle of virtual work applies to fast deformations.