Electric-field-induced B1-B2 transition in bent-core mesogens.
We report experimental results on two bent-shaped mesogens showing the B1 phase. Contrary to the conventional B1 structures, we have found that our compounds display a clear electro-optic effect in this phase. Under the influence of a 100-Hz square-wave electric field of moderate amplitude, an increase of the birefringence is observed. However, no switching current is detected, indicating that the materials remain antiferroelectric. For high enough fields, a drastic change in the texture occurs. This change is a phase transition to a B2 phase, and shows the typical antiferroelectric switching of this phase. The induced B2 phase has been identified to be homochiral. Upon removal of the field, the B1 structure is recovered. Our study is based on differential scanning calorimetry, x-ray, electro-optics, polarization reversal, and dielectric measurements.
Departamento de Física Aplicada II, Facultad de Ciencias, Universidad del País Vasco, Apartado 644, 48080 Bilbao, Spain. wmporapj@lg.ehu.es
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