Biaxial deformation of a polymer under shear: NMR test of the Doi-Edwards model with convected constraint release - art. no. 051809

H-2 NMR quadrupole interaction spectroscopy has been used to measure the de formation of a 670 kD poly(dimethylsiloxane) melt under shear in a Couette cell. The signals were acquired from a per deuterated benzene probe molecul e which provides a motionally averaged sampling of the entire segmental ens emble. We have measured the dependence on shear rate of the S-XX (velocity) , S-YY (velocity gradient), S-ZZ (vorticity), and S-XY (shear) elements of the segmental alignment tensor, as well as the angular dependence of the de uterium quadrupole splitting at fixed shear rate. We show that the data agr ee quite well with the Doi-Edwards theory but significantly better when con vected constraint release effects are included, These fits return a value f or the tube disengagement time of 100 ms.