新型二氟乙烯端基异硫氰酸酯化合物的合成及性能

摘要

Four kinds of new isothiocyanate liquid crystals composed of tolane core and difluorovinyl terminal group ( A1—A4 ) were synthesized via five step reactions based on 4-iodobenzaldehyde, and four ethyl analogues B1—B4 as comparison structures were also prepared. The structure characterizations of all related pro-ducts were performed using infrared spectrometer ( IR ) , 1 H-nuclear magnetic resonance ( 1 H NMR ) and mass spectrometer ( MS ) . The mesomorphic properties were investigated by differential scanning calorimeter ( DSC) and hot stage polarizing optical microscope( HS-POM) . The birefringence values and rotational viscosi-ty were extrapolated. The results showed that the target compounds A1, A2 and A3 exhibit wider nematic phase range(31—62℃). Replacement of ethyl chain by difluorovinyl as terminal group is enabled to not only enlarge the nematic phase temperature range but also increase birefringence(Δn=0038—0052) and reduce rotational viscosity. The high birefringence mixtures based new liquid crystals with terminal difluorovinyl sub-stitute have wider nematic phase range, higher birefringence, lower rotational viscosity and larger figure-of-merit( FoM) .%以对碘苯甲醛和二氟氯乙酸钠为原料,经5步反应合成了4个新型二氟乙烯端基异硫氰酸酯化合物,经气相色谱(GC)检测纯度均大于987％,总收率为23％～31％.采用红外光谱(IR),核磁共振波谱(NMR)和质谱(MS)等技术对化合物的结构进行了表征.通过差示扫描量热(DSC)法和偏光显微镜(POM)研究了化合物的介晶性,采用外推法得到了化合物的双折射率和旋转黏度值.结果表明,化合物A1～A3均呈现较宽的互变向列相;用二氟乙烯基替代乙基后,化合物的向列相拓宽了31～62℃,双折射率提高了0038～0052,旋转黏度降低.基于新型二氟乙烯基异硫氰酸酯化合物的高双折射率混合液晶配方具有更宽的向列相温度范围、更高的双折射率、更低的旋转黏度及更高的品质因子.