Journal of Chemical Physics vol:100 issue:10 pages:7736-7743
The dynamic response of Liquid crystalline polymers at high shear rates has been studied by measuring shear and normal stresses during transients following a step in the shear rate. Stepwise increase and decrease as well as flow reversals have been investigated. A solution of poly(benzylglutamate) (PBG) in m-cresol is used in the experiments. One purpose of the work is to perform a comparison with the theoretical predictions that apply to the case of spatially uniform. situations. The latter are expected to prevail at high shear rates, when the tumbling character of the nematic phase is effectively suppressed. The results indicate profound differences with respect to previous experiments at lower shear rates. A somewhat surprising result is that the behavior at high shear rates appears to be dominated by the viscous, rather than the elastic stress.