Abstract
Schiff base liquid crystals, known as [4-(hexyloxy)phenylimino)methyl]phenyl palmitate (IA), [4-(hexyloxy)phenylimino)methyl]phenyl oleate (IIA) and [4-(hexyloxy)phenylimino)methyl]phenyl linoleate (IIIA), were synthesized from palmitic, oleic, and linoleic natural fatty acids. The prepared compounds have been investigated for their thermal and optical behavior as well as phase formation using differential scanning calorimetry (DSC) and polarized optical microscopy (POM). Molecular structures of all studied compounds were confirmed via elemental analysis, FT-IR, 1H NMR, and 13C NMR. Smectic phase is the observed mesophase for all compounds; however, their type and range depend upon the terminal alkanoate chains attached to the phenyl ring. Computational calculations, Density functional theory (DFT), energy difference of the frontier molecular orbital (FMOs), as well as the thermodynamic parameters of different molecular configurations isomers were discussed. It was found that the mesophase behavior and the geometrical characteristics were affected by the degree of unsaturation of fatty terminal chains. Furthermore, the geometrical structure of the CH=N linkage plays an important role in the thermal stability and optical transition temperature.
Highlights
Optical displays and temperature/humidity sensors are important applications of liquid crystal (LC) in the field of instrumentation [1,2,3,4,5]
The FT-IR spectra of all investigated compounds (I–III)A were measured by PerkinElmer B25
These results indicate that the terminal alkoxy groups play an important role in the mesophase behaviors and their range of stabilities
Summary
Optical displays and temperature/humidity sensors are important applications of liquid crystal (LC) in the field of instrumentation [1,2,3,4,5]. Molecules 2019, 24, 4293 linkage to rigid phenyl rings provides a stepped core structure and retains the linearity of molecular structure It will enhance the stability of the mesophase [24]. Many researchers studied the design of the molecular deformation architecture influenced the mesophase formation [28,29,30,31], e.g., lattices of free space, fibers in twist-bend nematic phase [32,33], and oligomers [7,34,35,36] Many of these studies have involved the investigation of the impact of terminal substituents on the temperature of phase transition [37]. Flexible chains, mesogenic cores, and terminal groups play an important role in the designing of new thermotropic liquid crystals [41].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
