Synthesis, Optical, and Geometrical Approaches of New Natural Fatty Acids’ Esters/Schiff Base Liquid Crystals

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.

Induced Phases of New H-bonded Supramolecular Liquid Crystal Complexes; Mesomorphic and Geometrical Estimation

“…Most of the SMHLCs studied are based on the rod-like intermolecular H-bonding [10,[12][13][14][29][30][31] and there is a lot of interest towards the formation of angular supramolecular hydrogen-bonded liquid crystals [9]. On the other hand, the Schiff base and azo moiety are of special interest due to their ability for trans/cis isomerization upon UV light irradiations [7,[32][33][34][35]. In their supramolecular Schiff base/azo -based LCs, via H-bonding interactions, the rigid core is lengthened, and thus induces the mesomorphic behavior that may not occur in the individual components [11,36].…”

Thermal and Photophysical Studies of Binary Mixtures of Liquid Crystal with Different Geometrical Mesogens

“…Ester linkages are also commonly used, as they offer good advantages such as thermal and wide range of stability. Liquid-crystal-based Schiff base linkages have been synthesized and investigated in many interesting studies [42][43][44][45][46][47]. The development and investigation of new advanced functional thermotropic liquid crystals require the proper selection of a mesogenic core, linking group, and terminal functional substituents.…”

“…The development and investigation of new advanced functional thermotropic liquid crystals require the proper selection of a mesogenic core, linking group, and terminal functional substituents. [48] The photochromic phenomena for such spacers (-N=N, -N=CH-, and -COO-) are used to control the mesophase behavior and optical activities of several LCs [42,44,46,47,[49][50][51][52][53][54][55][56][57][58]. The reversible trans-cis isomerization, induced by thermal and ultraviolet irradiation, brings about a molecular ordering in the trans isomer that stabilizes the mesophase structure of the LC, while the disordering of cis isomers will destroy the mesophase formation.…”

A Novel Imine Based‐Liquid Crystal / PHBHHx Composite: Synthesis and Characterization

“…Liquid crystals containing Schiff base (CH=N) linkage have attracted a lot of attention in recent years . A 1,4‐disubstituted phenyl ring is used in order to provide a linear geometry to the molecule and molecular polarizability . It was reported that liquid crystals which have the p‐substituted phenyl groups that were bonded each other with a CH=N linkage group exhibit smectic phases.…”