4-硝基苯乙烯基吡啶类氢键液晶的合成及表征

Synthesis and Characterization of 4-(p-Nitrylstyryl)pyridine Hydrogen Bonded Liquid Crystals

该文用4-硝基苯甲醛和4-甲基吡啶合成了质子受体4-硝基苯乙烯基吡啶,用无水乙醇重结晶得黄色固体,其熔点126.8～128.9℃,产率27%。用4-羟基苯甲酸和1-溴代正烷合成了质子供体4-烷氧基苯甲酸,用体积分数为95%的乙醇重结晶,所得4种中间体产率都在20%左右。最后,以上述两个中间体为原料,制备了系列4-硝基苯乙烯基吡啶类氢键型液晶。IR和1H NMR证实了各中间体结构。POM、IR、DSC检测了各复合物。POM拍摄的向列相、近晶相液晶织构表明,3种该氢键复合物均呈现明显的液晶态,且n=3时为向列相,n=5、8时为近晶相;IR图谱3500～2500cm-1处峰的变化及羰基向高波数位移,证明了羧基和吡啶间的分子间氢键代替了羧基间的分子间氢键。各复合物的液晶区间范围比各相应单体增大了1倍,表明羧酸吡啶间氢键起到了稳定液晶态的作用。

The proton acceptor 4-（p-nitrylstyryl） pyridine was synthesized from 4-nitrobenxaldehyde and 4-methyl pyridine, and recrystalized with anhydrous ethanol. Its melting point was 126. 8 - 128.9℃, the yield was 27%. The proton donor 4-（p-alkyloxy ） benzoic acid were synthesized from 4- hydroxybenzoic acid and 1-bromic alkyl, recrystalized with 95% ethanol, the yield of the 4 intermediates were approximately 20%. Two intermediates were used to synthesize a series of intermolecular hydrogen bonded liquid crystals. The structures of all the intermediates were investigated by IR and ^1HNMR. The complexes were characterized by polarizing microscopy, IR and DSC. The photos taken by polarizing microscopy showed that 3 of these exhibited liquid crystal phases. It was found that nematic phase was formed when n = 3, smectic phase was formed when n = 5,8. The varieties of 3 500 - 2 500 cm^-1 and 1 700 cm^-1 in IR showed that the hydrogen bonding of carboxyl was substituted by those of carboxyl and pyridine. The range of liquid crystal phases became 2 times to the monomer showed the new hydrogen bonding played an important role in stabilized liquid crystal phases.