NonNewtonian Rheology in TwistBend Nematic Liquid Crystals
Abstract
A simple qualitative model has been presented to describe shear rheological behavior of the twistbend nematic liquid crystals (N_{TB}). It has been found that at relatively low shear rate ($\dot {γ } ≤slant {{\dot {γ }}_{{c1}}}$) the stress tensor σ created by this shear strain, scales as $σ ∝ {{\dot {γ }}^{{1/2}}}$. Thus, the effective viscosity decreases with the shear rate ($η ∝ {{\dot {γ }}^{{  1/2}}}$) manifesting socalled shearthinning phenomenon. At intermediate shear rate ${{\dot {γ }}_{{c1}}} ≤slant \dot {γ } ≤slant {{\dot {γ }}_{{c2}}}$, σ is almost independent of $\dot {γ }$ (a sort of plateau), and at large shear rate ($\dot {γ } ≥slant {{\dot {γ }}_{{c2}}}$), $σ ∝ \dot {γ }$, and it looks like as Newtonian rheology. Within our theory the critical values of the shear rate scales as ${{\dot {γ }}_{{c1}}} ∝ {{(\tilde {η }_{2}^{0}{/}\tilde {η }_{3}^{0})}^{2}}$, and ${{\dot {γ }}_{{c2}}} ∝ {{(\tilde {η }_{2}^{0}{/}\tilde {η }_{3}^{0})}^{4}}$, respectively. Here $\tilde {η }_{2}^{0}$ and $\tilde {η }_{3}^{0}$ are bare coarse grained shear viscosity coefficients of the effective smectics equivalent to the N_{TB} phase at large scales. The results of our work are in the agreement with recent experimental studies.
 Publication:

Soviet Journal of Experimental and Theoretical Physics Letters
 Pub Date:
 August 2022
 DOI:
 10.1134/S0021364022601397
 arXiv:
 arXiv:2207.02005
 Bibcode:
 2022JETPL.116..254K
 Keywords:

 Condensed Matter  Soft Condensed Matter;
 Condensed Matter  Statistical Mechanics
 EPrint:
 7 pages, 1 figure