一系列新的席夫碱型液晶高分子冠醚的合成与表征

SYNTHESIS AND CHARACTERIZATION OF A SERIES OF NOVEL SCHIFF BASE LIQUID CRYSTALLINE POLYMER CROWN ETHERS

以 4,4′ (α,ω 烷亚甲基二酰氧 )二苯甲醛和二氨基二苯并 1 5 冠 5为单体 ,采用溶液缩聚方法 ,合成了一类新的席夫碱型液晶高分子冠醚 .一种单体采用脂族二酰氯和对羟基苯甲醛反应制备 ,另一种新的单体采用二硝基二苯并 1 5 冠 5 ,在钯 碳催化剂存在下 ,水合肼还原制备 .合成的二硝基和二氨基 二苯并 1 5 冠 5 ,未能从IR和1 H NMR谱图上区分它们的几何异构体 .聚合物的分子量不高 ,Mn 在 1 0 1 0 0～ 1 3 0 0 0之间 .单体的结构通过元素分析、IR、1 H NMR和MS等方法确证 .聚合物的性质采用GPC、DSC、TG和POM等方法进行了研究 .发现所有的聚合物加热到各自的熔融温度 (Tm)以上都能形成液晶态 ,在液晶态可以观察到向列相的丝状织构和纹影织构 .聚合物的玻璃化转变温度 (Tg)、熔融温度和各向同性温度 (Ti)随聚合物分子中柔性间隔基的变化而变化 ,它们有较高的清亮点温度和宽的液晶态温度范围 .

A novel series of Schiff base type polymer liquid crystalline crown ethers was synthesized for the first time by solution polycondensation from 4,4'-(alkylene dioyloxy) dibenzaldyhyde (M-1) and diamino-dibenzo-15-crown-5 (M-2) as the monomers. Monomer M-1 has been synthesized by esterification reaction of aliphatdiyl chloride and 4-hydroxybenzaldehyde. Monomer M-1 has been synthesized by reduction reaction of dinitrodibenzo-15-crown-5 in the presence 10% Pd/C catalyst and hydrazine hydrate. The geometric isomers of dinitrodibenzo-15-crown-5 and diaminodibenzo-15-crown-5 that were synthesized for the first time can not be differentiated by IR spectrum and H-1-NMR spectrum. The molecular weights of the polymers are not high, and the M-n of the polymers ranges from 10100 similar to 13000. The monomer structures were identified by using elementary analysis, IR, H-1-NMR and MS etc. The properties of polymers were investigated by using GPC, DSC, TG, WAXD and POM. It was found that all the polymers went into a liquid crystal phase when heated to their melting temperature (T-m). The threaded texture and schlieren texture can be observed. The glass transition temperature (T-g), melting temperature and isotropization temperature (T-i) change with varing the flexible spacer unit in the polymers, all the polymers have higher clearning points and wide mesophase ranges. The WAXD study illustrated that the polymers of 6 I-a, 6 I-c, 6 IIb, and 6 IId are liquid crystalline with a nematic phase. A dispersive peak at 2theta near 20degrees appeared on their WAXD curves, which is a typical character for quenched nematic liquid crystal polymers.