Periodic pattern formation in an achiral bent core nematic

We investigated a periodic flexoelectric domain pattern, which appeared as regular parallel stripes in an achiral bent core nematic liquid crystal when dc electric field was applied. We found that such a pattern was first formed at the substrate surface and took place in sandwich cells with a gap larger than 2μm. The field-induced periodic pattern was preserved in the field-off state by a polymer network formed in the cell and was found to exhibit a polar as well as a linear electro-optic response due to in-plane switching of the sample optic axis. A comparison between this response and the one obtained in short cholesteric liquid crystals, aligned in ULH (uniform lying helix) texture, and short pitch ferroelectric liquid crystals, respectively, suggested that a heliconical molecular order is most probably formed in the field-induced periodic stripe pattern, with the helix axis orthogonal to the stripes. To our knowledge, this is the first experimental evidence of field-induced chiral-symmetry breaking in the flexoelectric periodic stripe pattern in achiral bent core nematic, resulting in heliconical molecular order, resembling the one of twist-bend (TB) nematic phase in this kind of nematics.