含冠醚环的席夫碱型液晶高分子的合成与表征

Abstract

以4,4′-(α,ω-烷亚甲基二酰氧)二苯甲醛和二氨基二苯并-14-冠-4为单体,采用溶液缩聚方法,首次合成了一类新的含冠醚环的席夫碱型液晶高分子.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-14-冠-4,在钯-碳催化剂存在下,水合肼还原制备.通过1H-NMR、13C-NMR和分子力学计算方法研究了二氨基二苯并-14-冠-4的两种异构体的空间立体结构,发现能从1H-NMR谱图上区分它们的立体结构.它们的立体结构近似属于Cs和C2群.聚合物的分子量不高,Mn在13000～24000之间.单体的结构通过元素分析、IR、1H-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.WAXD的研究进一步证实了聚合物的液晶性.

A novel series of Schiff base type liquid crystalline polymers with crown ether cycle was synthesized for the first time by solution polycondensation from 4,4'-(alkylene dioyloxy) dibenzaldyhyde (M-1), cis-diamino-dibenzo-14-crown-4 (M-2) and trans-cis-diamino-dibenzo-14-crown-4 (M-3) as the monomers. Monomer M-1 has been synthesized by esterification reaction of aliphatdiyl chloride and 4-hydroxybenzaldehyde. Monomers M-2 and M-3 have been synthesized by reduction reaction of cis-dinitrodibenzo-14-crown-4 and trans-dinitrodibenzo-14-crown-4 in the presence of 10% Pd/C catalyst and hydrazine hydrate. The stereo structures of cis-( trans)-dinitrodibenzo-14-crown-4 have been investigated by H-1-NMR, C-13-NMR and molecular mechanics theory. It was found that the stereo structures of cis-trans- and dinitrodibenzo-14-crown-4 can be differentiated by H-1-NMR spectrum, approximately belonging to groups C-s and C-2, respectively. The molecular weights of the polymers are not high, and the M-n of the polymers ranges from 13000 to 24000. 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 liquid-crystal phase when they were heated over 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 of the flexible spacer unit in the polymers. All the polymers have high clearing points and wide mesophase range. The WAXD study illustrated that the polymers of PIb, PId, PIIb and PIId are liquid crystalline with a nematic phase. A dispersive peak at 2theta near 20degrees appeared in their WAXD patterns, which is a typical character for quenched nematic liquid crystal polymers.