Synthesis And Characterization Of Novel Azobenzene Ionic Liquid Crystals

Ionic liquid crystals (ILCs) are a class of liquid-crystalline compounds containing anions and cations. Among liquid crystalline materials, the investigation of ionic liquid crystalline materials based on imidazolium salts is one of the most important and interesting liquid crystalline compounds. Ionic liquids show many useful properties such as very low vapor pressure, high thermal stability, non-flammability, high chemical stability, high ionic conductivity and wide electrochemical window, which may serve widely as a new generation of solvents in synthesis, catalysis, separation, and electrochemistry. Among the known ILCs, imidazolium salts are the most frequently studied, in which imidazoles can form ionic liquids and ionic liquid crystals by quaternization. The ionic interaction of imidazolium tends to stabilize lamellar mesophases, which shows great potential as ordered reaction media that can impart selectivity in reactions by ordering reactants. Incorporation of imidazolium ion functionalities into the paraffin side-chain terminated 4-nitroazobenzene derivatives could lead to a new series of liquid crystalline materials for research and industrial applications. We expected that the ionic interaction of imidazolium group could stabilize the mesophase of the azobenzene moiety over a wide temperature range, such azobenzene derivatives with a broad mesophase range are promising in high density optical data storage and photochemical devices.A novel series of compounds with different counteranions, 1-{[4-(4-nitrophenylazo) phenyloxy]} alkyl-3-methyl-1H-imidazol-3-ium bromide salts (C_n, n=3,6,10) and tetraflu oroborate salts (D_n, n=3,6,10) were synthesized by the incorporation of imidazolium group into the paraffin side-chain terminated 4-nitroazobenzene derivatives, respectively. A new series of ILCs, 1-(4-(4-nitrophenylazo)phenyloxy) vinyl-3-methyl-1H-imidazol-3-ium bromide salts(Cn, n=6, 10) were synthesized. In order to further investigate the effects of the ionic interaction on the mesophase of azobenzene liquid crystals, we incorporated two imidazolium groups into a azobenzene moieties via different length alkyl chains. Their chemical structures were determined by 1H NMR, 13C NMR, UV spectroscopy and elemental analysis. Our studies revealed that ionic interaction between imidazolium salts was the driving force for the formation of the monolayer smectic C, which enhances the thermal stability of the smectic state.Vinylimidazolium ion group-functionalised nitrophenylazo with different length of alkyl chains were reported in detail. We described the synthesis of these compounds and the characterization of their thermotropic liquid crystalline properties, moreover, the influence of ionic interaction between imidazolium salt on the mesomorphic properties was also explored. These results showed that the attached vinylimidazolium units induced the self-assembly of ILs and the occurrence of liquid crystalline phases. The introduction of vinylimidazolium group enhanced the thermal stability of the smectic state, which played an important role in forming the smectic layer structure.The ordered multilayers of azobenzene moiety with two symmetric substitution imidazolium ion groups (DC_n) and Au-cit nanoparticles were fabricated on the ITO substrate through the electrostatic layer-by-layer assembly technique. the growing process of multilayer growth was examined by UV–vis spectroscopy and cyclic voltammetry. We explored the role of azobenzene moiety in multilayers. The ordered multilayers are promising in high density optical data storage and photochemical devices.