Modification of the electro-optical properties of the B1 liquid-crystal phase using a rodlike liquid-crystal dopant.

It has recently been observed that on application of an alternating electric field, the B1 liquid-crystalline phase may be induced to form a switchable phase. This induced phase has been shown to have an almost thresholdless dielectric response. In this paper we examine this E-field-induced transition as a function of temperature both with and without a ferroelectric liquid-crystal dopant. Although the aim of this experiment was to enhance and stabilize the field-induced phase on addition of dopant, we find that the opposite is the case. The ferroelectric dopant actually increases the threshold E-fields required for transformation to the switching phase and at just 5 wt?% dopant a smectic-A phase is formed. Addition of the dopant also acts against the low-field switching and significantly speeds relaxation back to the B1 phase on field removal. In addition we find that the field-induced phase experiences a slower crystallization. We use polarized optical microscopy, differential scanning calorimetry, and x-ray scattering experiments to characterize the physical properties of the mixtures.