Cybotactic nematic liquid crystal – an overview

The recent identification of ferroelectricity within the nematic phase of liquid crystals has triggered significant interest. However, prior to this discovery; the potential existence of ferroelectricity in the nematic phase had already been investigated in the context of cybotactic nematic phases of liquid crystals. Ferroelectricity has previously been reported in chiral and achiral smectic phases. While the presence of nano-sized smectic clusters in the nematic phase of rod-shaped molecules, termed as cybotactic nematic, was recognised, it did not earn substantial attention. However, the cybotactic nematic phase in bent-core mesogens has gained significant attention due to its unconventional ferroelectric-like behaviour. To link the recent advancements in understanding ferroelectricity in the nematic phase, a comprehensive review has been conducted on the cybotactic nematic phase. This review encompasses a foundational explanation of the cybotactic model, followed by an overview of cybotactic phases in rod-shaped mesogens. The central focus lies in evaluating cybotactic phases within bent-core nematic systems, covering early debates, fundamental experimental evidences, and a compilation of mesogens that exhibit the cybotactic nematic phase. Furthermore, the review describes into the physical attributes of mesogens featuring cybotactic nematic phases, including discussions on repolarisation, dielectric properties, and optical characteristics.