Photoresponsive Chiral Dopants: Light‐Driven Helicity Manipulation in Cholesteric Liquid Crystals for Optical and Mechanical Functions

Abstract This Review focuses on recent advancements regarding the design of photoisomerizable chiral dopants which can switch the helical orientation in cholesteric liquid crystals upon light stimuli. Chiral dopants exhibiting conformational change in response to an external stimulus can provide dynamic control of the cholesteric pitch. Development of such responsive systems has been attempted since the 1970s. However, major advances on efficient chiral dopants exhibiting either high helical twisting power or large photoswitching have been achieved only in recent years. This Review covers photoresponsive low molecular weight cholesteric liquid crystal systems based on chiral dopants capable of photochemically “switching power to twist” surrounding liquid crystalline host molecules, “inverting” their handedness or even “inducing” helical organization from the racemic nematic phase.