Synthesis And Characterization Of New Schiff Base-type Liquid Crystal Crown Ethers

Liquid crystal crown ether is a kind of compound, which remains the liquid crystal property when the crown ether ring link or insert to the molecular structure of liquid crystalline compound. It is in fine-order structure and unite its function and character into together. So it is a kind of novel compound with the characterstic of liquid crystal and the selecting of the crown ether. And they are different with the common liquid crystal compound in the molecular structure, property and application function. Up to now, people have more interest on the them in the field of transferring signal and information at the molecular level.Starting from the molecular design, three novel series of Schiff base type liquid crystal crown ethers were synthesized. According to the size of crown ether ring, the end alkoxyl groups and the conformation of compounds, six series of Schiff's base liquid crystal crown ethers composed of 24 compounds were constructed.The chemical structure of them: Series I and series II:cis-4,4'-bis[(4'-alkoxybiphenyl-4-carboxy)benzylideneamino]dibenzo-18-crown-6 trans-4,4'-bis[(4'-alkoxybiphenyl-4-carboxy)benzylideneamino]dibenzo-18-crown-6 SeriesIII and series IV:4,4'-bis[(4'-alkoxybiphenyl-4-carboxy)benzyiideneamino]dibenzo-15crown-5 SeriesV and series VI:cis-4,4'-bis[(4'-alkoxybiphenyl-4-carboxy)benzylideneamino]dibenzo-14-crown-4 trans-4,4'-bis[(4'-alkoxybiphenyl-4-carboxy)benzylideneamino]dibenzo-14-crown-4The DNDB14C4, DNDB15C5, DAmDB14C4 and DAmDB15C5 are novel compounds.The chemical structure of these compounds were identified by using elemental analysis, infrared spectrum, nuclear magnetion reasonance, and mass spectrometry. Their liquid-crystalline behavior was characterized by differential scanning calorimetery(DSC), polarizing optical microscopy(POM), and polarimetric analysis. Systemic research including the influence of the crown ether ring's symmetry, the size and the conformation on the liquid-crystalline behavior have been done in this paper. The synthesis way and method were improved.From the experimental results, it was found that:1, Compounds 2,4,16,17 and 18 have liquid crystal properties.2, Upon heating to their respective melting temperature, all the compounds above went to liquid crystal phase. The typical chiral smectic C phase lined texture and finger print texture,smectic fan texture and broken fan shaped texture, nematic Schlieren texture Schlieren texture and ball grandle texture, paramorphosis texture can be observed.3, The liquid crystalline texture of all the compounds can be kept for a long time at room temperature upon quenching from the melt.4, All the compounds in their liquid crystal state can be easily oriented in the direction of external force.5, Both melting point(Tm) and isotropization temperature(Tj) of all the three series compounds change regularly with the carbon numbers of the end alkoxy group increased. There is a gradual increase in smectic phase length and in the smectic-nemetic transition temperature. At the same time there is a gradual decrease in nemetic phase length.The compounds with symmetric structure and different size crown ether rings, 16 and 18, have higher Tm and Tj than those of the compounds 17 with the asymmetric structure. The Tm and Ti of compounds 18 is higher than the compounds 16.The Tm and Tj of compounds 18 II and 16 II which have the trans conformation is higher than those of compounds 18 I and 16 I having cis conformation.The Tm and Tj of the compounds 17 II synthesized from the higher Tm AmDB15C5 is higher than those of compounds 171.It was found that the changes of the liquid crystal phase have corresponding relationship to the photos of all three series of compounds separately.6, The optical rotation of compounds with chiral center was tested by rotationally analysis instrument, it was found that the rotation was maintained during the synthesis process.