材料期刊网

合成了16个三氟丙炔为端基的液晶化合物,以苯甲醛衍生物与1,1,1-三氯三氟乙烷的有机锌试剂进行加成脱水成烯,再通过Suzuki偶联反应后脱去HCl制得目标产物,总产率>67%,气相色谱(GC)纯度>99.5%,通过红外光谱(IR)、核磁共振谱(NMR)和质谱(MS)确定其结构. 利用DSC和POM对该类化合物的热性能进行了测试,结果表明,联苯类的化合物不具有液晶相,而三联苯类的化合物具有近晶A相,且熔点随烷基链碳原子的增加呈下降趋势. 物理性能测试结果表明,该类化合物的Δε值为12.61~21.94,末端三氟甲基基团和侧氟的引入可以有效的增加Δε值;Δn值0.19~0.29,随分子内苯环数目的增加而变大;γ1值为49.9~468.0 mPa·s,随分子内苯环数量的增加而增加. 化合物4n具有高Δε(>19.2)、高ε⊥(>10.3)及低Δε/ε⊥(<1.9). 通过模拟计算讨论了炔键位置对此类液晶材料性质的影响. 该类化合物在调节混合液晶介电各向异性和双折射率方面有很好的应用价值,同时通过分子结构的改进也可以很好地应用于FFS(fringe-field switching)显示模式.

Sixteen liquid crystals with 3,3,3-trifluoropropynyl terminal group were reported.The target compounds were synthesized via a series of reactions including the zinc reagent's reaction, Suzuki cross-coupling, and the elimination reaction of HCl.The total yields are more than 67%, and the gas chromatograph(GC) purities are more than 99.5%.The structures of the target compounds were characterized by infrared spectroscopy(IR), nuclear magnetic resonance(NMR) and mass spectrometry(MS).Moreover, their thermal properties were investigated by differential scanning calorimetry(DSC) and polarizing microscope(POM).The results show that the biphenyl type of compounds exists no liquid crystal phase while the terphenyl compounds have a smectic A phase.The melting points drop with the increase in the number of alkyl chain carbon.In terms of physical properties, these compounds have large Δε value(12.61~21.94), and the value of Δε is increased by trifluoromethyl and lateral fluorine substitution.The Δn value is about 0.19~0.29 with the increase of the number of benzene rings.The γ1 value is in the range from 49.9 to 468.0 mPa·s, which goes up with the increase of the number of benzene rings.Compounds 4n have high Δε(>19.2), high ε⊥(>10.3), and low Δε/ε⊥(<2).The influence of the position of the acetylenic bond on the properties of this kind of liquid crystal was discussed by simulation.All of the above properties of these liquid crystals have been proved to be useful for tuning the birefringence and the dielectric anisotropy of the liquid crystal mixtures, and these liquid crystals also have good value for FFS(fringe-field switching) display mode by the improvement of molecular structure.