Nematic Aromatic Esters, The Synthesis And Characterization Of Thermotropic Liquid Crystal

Liquid crystals are beautiful, mysterious, and extremely useful which provide scientists and engineers with one of the most attractive and fascinating fields of scientific and industrial research around the world. Their dual nature and easy response to electric and magnetic have generated lots of applications and uses which keep growing rapidly nowadays. In this paper, we researched one kind of nematic liquid crystals which linking group is ester (-COO-). The generic name of the liquid crystal is phenyl benzoate (ester). The phenyl benzoate (ester) liquid crystal is important both in chemical industry and electronic industry. It is not only a kind of important materials, but also is a critical part as mesogen unit or monomer in liquid crystal polymer.Based on these background, we began our work. In this paper we not only designed and synthesized1,4-di(4-methoxybenzoyl)oxy benzene, bis(4-(ethoxycarbonyl)phenyl) terephthalate, bis(4-methoxyphenyl) terephthalate, di(biphenyl) terephthalate,4-(ethoxycarbonyl)phenyl4-methoxyphenyl terephthalate, allyl4-methoxyphenyl terephthalate,4-(ethoxycarbonyl)phenyl allyl terephthalate et cetera several phenyl benzoate (ester) liquid crystal compounds, but also we discussed the ways of synthesis, purification and the factors influenced the yield during the process.All the seven compounds were synthesized by the similar way. Take the first compound-1,4-di(4-methoxybenzoyl)oxy benzene for example. It was synthesized by the reaction of hydroquinone and4-methoxybenzoyl chloride in the presence of triethylamine using THF as solvent. We finally got the white crystal of the compound when the mixture with solid suspension coming from the reaction was purified properly. The structure of these compounds were proved by Fourier transform infrared spectra (FT-IR), gas chromatography/mass spectrometry (GC/MS) and nuclear magnetic resonance (NMR) and the thermotropic liquid crystalline phase of these compounds were proved by differential scaning calorimetry (DSC), simultaneous thermal analysis (STA), thermogravimetry (TG) and polarization optical microscopy (POM). All these compounds we have synthesizd were thermotropic liquid crystals and purified very well.At the end of this paper, we tried to synthesize the side chain liquid crystal polymers. Based on the monomers we synthesized before, we explored the ways of polymerization. Otherwise, we also tried to synthesize the side chain liquid crystal polymers by the reaction of poly (ethylene glycol) methacrylate (PEGMA) and the mesogen units. Although we finally didn’t get the ideal polymers, we found out the factors and the difficulty in the reaction. We hope that the work we have done could provide some basic technology on the synthesis and purification of liquid crystalline for others.