A Review of Schiff Base Liquid Crystals on Their Structure–Property Relationships

Smart materials called liquid crystals (LCs) exhibit properties between those of liquids and solids through the formation of different phases, such as nematics (N) and smectics (Sm). Among several linking units, the Schiff base (‐C=N‐) has proven to be highly beneficial for LC behavior because of its capability to induce molecular planarity, strong dipole moment, and extended π ‐conjugation. This review has analyzed structural property correlation in Schiff base LC while emphasizing the imine linkage, combinations of alkyl/alkoxy chains, halogen substitutions, thermal stability, mesophase type, and mesophase temperature range. Comparative studies have been reported across molecular series, revealing how a change in terminal chains encourages packing and ordering in the LC molecules, while fine adjustments in molecular packing and polarity are made by halogen substituents. This review also discusses the role of imine in comparison with azo and ester to understand their contributing factors responsible for their properties.