DEPENDENCE OF FLOW BEHAVIOR OF NEMATICS IN SHEAR ON THE FORM OF THE MEAN-FIELD POTENTIAL

The dynamic transition of nematics in (slow) shear from flow-aligning to tumbling behaviour is here predicted by using the rigid rod-like mo lecular model together with an extension of the Maier-Saupe mean-field potential. Such an extension, already available in the literature wit h reference to equilibrium data, includes interactions of rank higher than the basic quadrupolar one considered by Maier and Saupe. The theo retical predictions are then compared with the few existing sets of dy namic data. Although an acceptable qualitative agreement is found, the theory generally overpredicts the value of the relevant ratio alpha3/ alpha2 of Leslie coefficients.