Development of Polar Order in the Liquid Crystal Phases of a 4-Cyanoresorcinol-Based Bent-Core Mesogen with Fluorinated Azobenzene Wings

A bent-core mesogen consisting of a 4-cyanoresorcinol unit as the central core and laterally fluorinated azobenzene wings forms four different smectic LC phase structures in the sequence SmA-SmCs-SmCsPAR-M, all involving polar SmCsPS domains with growing coherence length of tilt and polar order on decreasing temperature. The SmA phase is a cluster-type deVries phase with randomized tilt and polar direction; in the paraelectric SmCs phase the tilt becomes uniform, although polar order is still short-range. Increasing polar correlation leads to a new tilted and randomized polar smectic phase with antipolar correlation between the domains (SmCsPAR) which then transforms into a viscous polar mesophase M. As another interesting feature, spontaneous symmetry breaking by formation of a conglomerate of chiral domains is observed in the non-polar paraelectric SmCs phase.