Mesomorphic Characteristics of Liquid Crystalline Esters<i>p</i>-Methoxyphenyl<i>p</i>-Alkoxycinnamates
作者:Jayrang S. Dave、K. P. Dhake
DOI:10.1246/bcsj.65.559
日期:1992.2
The newly synthesized homologous series p-methoxyphenyl p-alkoxycinnamates (I) can be compared with the series N-[p-(p-alkoxycinnamoyloxy)benzylidene] p-anisidines (II).1) All the homologues of both the series (I) and (II) from C1 to C18 are mesogens. In series (II) the first five members decompose due to high transitions at about 300 °C. With decrease in length of the molecules of series (I) than that of series (II), the overall transitions also decrease by about 150 °C. The first seven members in series (II) are nematogens; polymesomorphism begins from octyloxy homologue with the commencement of smectic mesophase and continues to be exhibited upto the last i.e. octadecyloxy homologue. In series (I) also the nematic phase is exhibited upto the heptyl derivative; the smectic phase commences from C8-member in the form of monotropic phase thereby exhibiting polymesomorphism upto the C14 homologue. The last two members of series (II) are smectogens. The odd-even effect is missing in series (II) whereas in series (I), it is seen upto the fifth homologue. In both the series, the N-I curves show a falling tendency— a criterion of high melting series. From textures’ point of view both the series have common features, the nematic phase is threaded when it is the only mesophase shown and homeotropic in polymesomorphic region, whereas the smectic mesophase is focal conic fan shaped of smectic-A variety. This series also yields interesting comparison with the series (III) p-nitrophenyl p-alkoxycinnamates4) and (IV) p-chlorophenyl p-alkoxycinnamates.5)
新合成的同系物系列p-甲氧基苯基p-烷氧基肉桂酸酯(I)可以与系列N-[p-(p-烷氧基肉桂酸酯氧基)苯甲亚胺] p-氨基香豆素(II)进行比较。两系列(I和II)中的所有同系物,从C1到C18都是液晶物质。在系列(II)中,前五个成员因在约300°C时的高转变而分解。由于系列(I)的分子比系列(II)短,整体转变温度也降低了约150°C。系列(II)的前七个成员是向列相物质;多晶相从辛氧同系物开始,伴随形成层状液晶相,并持续到最后一个,即十八烷氧同系物。在系列(I)中,向列相一直展现到庚基衍生物;层状相从C8成员开始,以单调相的形式展现,从而在C14同系物之前显示多晶相。系列(II)的最后两个成员是层状成相物。系列(II)中缺乏奇偶效应,而在系列(I)中,奇偶效应一直存在到第五个同系物。在两个系列中,N-I曲线显示出下降趋势——这是高熔点系列的特征。从纹理的角度来看,这两个系列具有共同特征,当液晶相仅为向列相时呈现出穿-threaded状态,在多晶相区域为同向对称,而层状液晶相则呈现放射状锥形(层状A型)。该系列还与(III)p-硝基苯基p-烷氧基肉桂酸酯和(IV)p-氯苯基p-烷氧基肉桂酸酯进行有趣的比较。