Non-Newtonian Rheology in Twist-Bend Nematic Liquid Crystals
Abstract
A simple qualitative model has been presented to describe shear rheological behavior of the twist-bend nematic liquid crystals (NTB). 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 so-called shear-thinning 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 ${{\dot {γ }}_{{c1}}} ∝ {{(\tilde {η }20{/}\tilde {η }30)}2}$, and ${{\dot {γ }}_{{c2}}} ∝ {{(\tilde {η }20{/}\tilde {η }30)}4}$, respectively. Here $\tilde {η }20$ and $\tilde {η }30$ are bare coarse grained shear viscosity coefficients of the effective smectics equivalent to the NTB 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
- E-Print:
- 7 pages, 1 figure