Mesophase behaviour of laterally di-fluoro-substituted four-ring compounds

Abstract

Four new groups of the di-fluoro-substituted 4-(2′-(or 3′)-fluoro phenylazo)-2-(or 3-) fluoro phenyl-4″-alkoxyphenylazo benzoates (In-IVn) were prepared and investigated for their mesophase behaviour. An alkoxy group of variable chain length (n = 6, 10 and 14 carbons) is attached to the terminal phenylazo benzoate moiety, and two lateral fluoro substituents are attached individually with different orientations to the other two adjacent rings. The molecular structures of the prepared compounds were confirmed by Fourier transform infrared spectroscopy and 1 H NMR spectroscopy. The study aims to investigate the steric effect of the spatial orientation and relative positions of the two lateral fluorine atoms on the mesomorphic properties in their pure states. The mesophase behaviour was investigated via differential scanning calorimetry and mesophases were identified by polarised light microscopy. The investigation shows that these compounds exhibit high enantiotropic mesophases (SmC and N) and broad mesophase temperature range. The type and stability of the mesophase depends on the length of the terminal alkoxy chain and the position the two fluoro substituents. A comparison between these investigated compounds with their corresponding three-ring analogues was discussed.

Experimental and Theoretical Approaches of New Nematogenic Chair Architectures of Supramolecular H-Bonded Liquid Crystals

“…Furthermore, the addition of lateral Cl atom in supramolecular architectures weakens the side by side cohesion interactions thus enhances a nematic phase for all 1:1 complex. Furthermore, the molecular geometry and size of the lateral substituent impact the mesophase stability and the polarizability of the whole molecule [22,23,66]. It was found that the length of the alkoxy chain, the polarity as well as the position (or orientation) of the lateral group are important factors determining the type and the range of the mesophase.…”

“…[18,19] An incorporation of lateral groups with different size and polarity widely improves many characteristics of liquid crystalline materials. It could be attributed to the disturbance in the molecular packing that decreases the melting temperature and thermal stability of liquid crystal mesophases [20][21][22][23][24][25][26][27]. Lately, azopyridines have been used in the formation of nano-fiber supramolecular self-assembling and hydrogen/halogen-bonding LCs with photo-induced transition phenomena [28][29][30][31][32].…”

Nematogenic Laterally Substituted Supramolecular H-Bonded Complexes Based on Flexible Core

“…The attachment of heterocyclic moiety in the mesomorphic compounds strongly affects polarity and/or polarizability, as well as the geometric arrangement. In addition, the molecular size and shape of the lateral group affects the mesophase stability and the polarizability [45,46]. chain length (n), thus the stability of the N phase is affected by the length of alkoxy chain.…”

Experimental and theoretical approaches of new nematogenic chair architectures of supramolecular H-bonded liquid crystals

“…It could be attributed to the disturbance in the molecular packing that decreases the melting temperature and thermal stability of liquid crystal mesophases. [17][18][19][20][21][22][23][24]. Lately, azopyridines have been used in the formation of nano fiber supramolecular self-assembling and hydrogen/halogen-bonding LCs with photo induced transition phenomena.…”

“…From the present investigation, it would be expected that, the increment in the molecular anisotropy due to the orientation of the lateral electron-withdrawing Cl atom in the supramolecular geometry impacted the stability of nematic phase that agrees with our previous work[31,61].Furthermore, the addition of lateral Cl atom in supramolecular architectures weakens the side by side cohesion interactions thus enhances a nematic phase for all 1:1 complexes. In addition, the molecular geometry and size of the lateral substituent impact the mesophase stability and the polarizability of whole molecule[19,20,62]. It found that the length of the alkoxy chain, the polarityas well as the position (or orientation) of the lateral group are importance factors in determining the types and the range of the stability of the mesophase.…”