Viscosity Measurement in Ferroelectric Liquid Crystals Using a Polarization Switching Current

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Abstract
A new method to evaluate rotational viscosity η in ferroelectric liquid crystals is proposed. This method is based on the measurement of a polarization switching current upon field reversal. It is shown that a full width at half-maximum of the current peak t w is equal to 1.76η/P s E, while the area gives twice the spontaneous polarization P s. It is also shown that the sign of a dielectric anisotropy Δε is determined by the asymmetrical shape of the signal. A proportionality between t w and E -1 was confirmed for a surface stabilized ferroelectric liquid crystal cell. The temperature dependences of P s and η are presented.