LAUSR

The electroviscous effect deals with the change in the viscosity of fluids due to an external electric field. Here, we report experimental studies on the electroviscous effects in a ferroelectric nematic liquid crystal. It was synthesised accomplishing a new synthetic route which provides higher yield than conventional one. We measure electric field-dependent viscosity under a steady shear at different temperatures. In the low field range, the increase in viscosity ($\Delta\eta=\eta(E)-\eta_0$) is proportional to $E^2$ and the corresponding viscoelectric coefficient ($f\approx10^{-9}$m\textsuperscript{2}/V\textsuperscript{2}) of the ferroelectric nematic is 2 orders of magnitude larger than the apolar nematic liquid crystals and largest ever measured for a fluid. The apparent viscosity measured under a high electric field shows a power-law divergence $\eta\sim(T-T_c)^{-0.7\pm0.05}$, followed by nearly an order of magnitude drop below the N-N\textsubscript{F} phase transition. Experimental results within the dynamical scaling approximation demonstrate rapid growth of polar domains under a strong electric field as the N-N\textsubscript{F} phase transition is approached. The gigantic electroviscous effects demonstrated here are important for emerging applications and understanding striking electrohydromechanical effects in ferroelectric nematic liquid crystals.