新型低聚噻吩衍生物的设计、合成及其液晶性能的研究

设计、合成了一系列新型低聚噻吩衍生物N,N’-双烷烃基-5,5’-二溴基-2 ,2’：5’,2’-三噻吩-4,4’-二酰胺N,N’-dialkyl-5,5’-dibromo-2,2’:5 ’,2’-terthiophene-4,4’-dicarboxamide](DNCnDBr3T,n=5,8,6,18)。示差扫描 量热法（DSC）测定的结果及偏光光学显微镜观察的结果显示,DNC18DBr3T, DNC16DBr3T,DNC8DBr3T具有近晶A形液晶性质,DNC5DBr3T不具有液晶性质。为了探 讨分子间氢链对液晶形成的影响,设计、合成了新型低聚噻衍生物4,4“-双烷烃 酯-5,5“-二溴基-2,2’:5’,2’-三噻吩4,4’-bis(alkyloxycarbonyl)-5,5’ -dibromo-2,2’:5’,2’-terthiophene](DOCnDBr3T,n=5,8,16,18).测定和观察的 结果发现,DOCnDBr3T(n=5,8,16,18）不具有液晶的结果。这个结果表明,酰胺基 的存在于液晶的形成起着重要的作用。测定DNC18DBr3T在结晶状态和液晶状态下的 红外光谱,进一步证实了部分分子间氢键对于液晶的形成起着重要的作用。

Synthesis and Liquid Crystal Properties of a Novel Class of Oligothiophene Derivatives

With the aim of developing new oligothiophene-based liquid crystals involving hydrogen bonding, new terthiophene derivatives containing an alkylamide group, N,iV'-dialkyl-5,5"-dibromo-2,2':5',2"-terthiophene-4, 4"-dicarboxamide (DNCnDBr3T, n = 5, 8, 16, 18), were designed and synthesized, and their thermal behaviors were examined. While DNCnDBr3T compounds with n = 8, 16, 18 were found to form smectic A phase, DNC5DBr3T did not form liquid crystal phase. In addition to liquid crystal behavior, crystal polymorphism was also observed for DNCigDBr3T. It is shown that the alkyl chain length greatly affects liquid crystal phase formation. The absence of liquid crystallinity in the corresponding ester derivatives suggests that intermolecular hydrogen bonding plays a role in the formation of liquid crystal phase in the DNCnDBr3T system.