Nonlinear viscoelasticity in nematics

Note that this increases with concentration the nonlinear effect is expected to be less pronounced at higher concentration. 

The result of more detailed calculation is shown in Fig. 10.8, where the steady-state viscosity at various shear rates is plotted against concentration. The characteristic feature is that as the shear rate increases the maximum of the viscosity decreases. This agrees at least qualitatively with experiments (see Fig. 10.9). 

On the other hand, curious nonlinear effects have been observed in some polymeric nematics. Kiss and Porter found that with increasing shear rate, the first normal stress difference becomes negative and then becomes positive again. This effect is not explained by the present constitutive equation and some other physical reason appears to be needed. 

---