ABSTRACT Two series of novel four-arm azobenzene liquid crystal molecules were designed and synthesized, and their mesophase properties, photo-induced transition were studied. Two series of mesogenic arms were screened with different length of flexible chain (the carbon number n of flexible chain is 4, 6, 8, 10) using methoxy and nitro as terminal substituents R. The four-arm azobenzene LCs were synthesized by introducing the mesogenic arms into cholic acid. FACAE-O-n, FACAE-N-n all belonged to photosensitive thermotropic enantiotropicnematic LCs. For methoxyl series, melting transitions (Tm), liquid crystal-isotropic transitions (Ti) and mesogenic ranges decreased with the increase of carbon numbers in flexible chain both on heating and cooling. The mesophase performance of FACAE-O-4 was the most excellent. For nitro series, Tm and Ti on heating and cooling decreased with the increase of carbon numbers. Nevertheless, mesogenic ranges increased with the increase of carbon numbers only on heating. The cooling mesogenic ranges showed a trend of rising firstly and then falling, reaching the maximum 103.1oC (n=8). Under ultraviolet irradiation, there was no red shift. The intensity of maximum absorption has changed with the increase of ultraviolet irradiation time. After photo-induced, Tm and Ti on heating and cooling of the four-arm LCs decreased, and the mesogenic ranges became shorter. Graphical abstract

中文翻译：

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基于胆酸的具有不同长度介晶臂的非常规多臂偶氮苯液晶：合成、中间相性质和光致转变

摘要 设计合成了两个系列的新型四臂偶氮苯液晶分子，并研究了它们的中间相性质、光致转变。以甲氧基和硝基作为末端取代基R，筛选出具有不同长度柔性链（柔性链的碳数n为4、6、8、10）的两个系列介晶臂。介晶臂转化为胆酸。FACAE-On、FACAE-Nn 均属于光敏热致对映体液晶。对于甲氧基系列，熔融转变（Tm）、液晶各向同性转变（Ti）和介晶范围随着柔性链中碳数的增加而在加热和冷却时降低。FACAE-O-4的中间相性能是最优秀的。对于硝基系列，加热和冷却时的Tm和Ti随着碳数的增加而降低。然而，仅在加热时，介晶范围随着碳数的增加而增加。冷却介晶范围呈现先升后降的趋势，最高达到103.1oC（n=8）。在紫外线照射下，没有红移。最大吸收强度随着紫外线照射时间的增加而变化。光诱导后，四臂液晶的加热和冷却的 Tm 和 Ti 降低，介晶范围变短。图形概要 在紫外线照射下，没有红移。最大吸收强度随着紫外线照射时间的增加而变化。光诱导后，四臂液晶的加热和冷却的 Tm 和 Ti 降低，介晶范围变短。图形概要 在紫外线照射下，没有红移。最大吸收强度随着紫外线照射时间的增加而变化。光诱导后，四臂液晶的加热和冷却的 Tm 和 Ti 降低，介晶范围变短。图形概要