Chirality transfer from atropisomeric chiral inducers to nematic and smectic liquid crystals – synthesis and characterization of di- and tetra-substituted axially chiral binaphthyl derivatives
作者:Munju Goh、Jinwoo Park、Yehdong Han、Sangbum Ahn、Kazuo Akagi
DOI:10.1039/c2jm35282f
日期:——
The chirality transfer of axially chiral binaphthyl derivatives bearing liquid crystal (LC) moieties at the n,nâ² positions (n = 3, 4, 6) of the binaphthyl rings to nematic (N) and smectic (S) LCs is investigated. Chiral nematic LCs (N*-LCs) are prepared by adding a small amount of the chiral binaphthyl derivative into host N-LCs composed of cyanobiphenyl mesogen cores. The binaphthyl derivative with phenylcyclohexyl (PCH) type LC moieties at the 4,4â² positions of the binaphthyl ring [D-4,4â²] exhibits a low helical twisting power (HTP) of 11 μmâ1. In contrast, those with LC moieties at the 3,3â² and 6,6â² positions of the binaphthyl rings [D-3,3â² and D-6,6â²] exhibit high HTPs of 153 μmâ1 and 154 μmâ1, respectively. Next, the binaphthyl derivatives are added into two types of S-LCs with phenylbenzoate mesogen cores: 4-(4-methylpentyloxy)phenyl-4-(decyloxy)benzoate [PhB1] and 4-(3-methylpentyloxy)phenyl-4-(decyloxy)benzoate [PhB2]. The mixture of the host LC, PhB1 or PhB2 with the chiral dopant, D-3,3â² or D-6,6â² shows chiral smectic LCs C (SC*-LCs). The highly twisted SC* phases with helical pitches of 1.2â1.4 μm are prepared in PhB1 and PhB2 by using the chiral dopant of D-6,6â². It is concluded that D-6,6â² has a large helical twisting power and is the most favourable atropisomeric chiral inducer for chirality transfer to both N-LCs and S-LCs.
研究了具有液晶(LC)基团的轴手性二萘衍生物在二萘环的n,n'位(n = 3, 4, 6)向向列相(N)和层状相(S)液晶的手性转移。通过将少量手性二萘衍生物添加到由氰基二苯基介质核心组成的主导N-LC中,制备了手性向列相液晶(N*-LCs)。在二萘环的4,4'位具有苯基环己基(PCH)类型液晶基团的二萘衍生物[D-4,4']显示出低的螺旋扭转能力(HTP)为11 μm⁻¹。相比之下,在二萘环的3,3'和6,6'位具有液晶基团的衍生物[D-3,3'和D-6,6']分别显示出高的HTP,分别为153 μm⁻¹和154 μm⁻¹。接下来,将二萘衍生物添加到两种具有苯基苯甲酸酯介质核心的S-LC中:4-(4-甲基戊氧基)苯基-4-(癸氧基)苯甲酸酯[PhB1]和4-(3-甲基戊氧基)苯基-4-(癸氧基)苯甲酸酯[PhB2]。主液晶PhB1或PhB2与手性掺杂剂D-3,3'或D-6,6'的混合物显示出手性层状液晶C(SC*-LCs)。通过使用手性掺杂剂D-6,6'在PhB1和PhB2中制备了具有1.2–1.4 μm螺旋间距的高度扭曲SC*相。得出的结论是,D-6,6'具有较大的螺旋扭转能力,并且是向N-LC和S-LC进行手性转移的最有利的对映异构体手性诱导剂。