Rheology of a Twist-bend Nematic Liquid Crystal SEYYED

ow shear alignment studies and rheological measurements in the twist-bend nematic (Ntb) liquid crystalline phase of odd numbered exible dimer molecules is presented. It is found that the Ntb phase is strongly shear-thinning. At shear stresses below 1Pa the apparent viscosity of the Ntb phase is 1000 times larger than in the nematic phase. At stresses above 10Pa the Ntb viscosity drops by two orders of magnitude and the material exhibits Newtonian uid behavior. The results are consistent with the behavior of a system with pseudo-layer structure with layer spacing determined by the heliconical pitch. From the measurements of dynamic modulus we estimate the compression modulus of the pseudo-layers to be B 2kPa; this value is discussed within the context of a simple theoretical model based upon a coarse-grained elastic free energy.