Liquid crystal dimers and the twist-bend nematic phase. The preparation and characterisation of the α,ω-bis(4-cyanobiphenyl-4′-yl) alkanedioates

Lü, Zhou; Henderson, Peter A.; Paterson, Brodie; Imrie, Corrie T.

doi:10.1080/02678292.2014.888803

Cited by 87 publications

(30 citation statements)

References 78 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The simplest oligomer is known as the dimer in which two mesogenic units are linked by a single flexible spacer. Many series of dimeric liquid crystals have been reported, [1][2][3][4][5] all of these compounds may be termed symmetric, with identical mesogenic moieties, or non-symmetric dimers, with different mesogenic units. In both cases, the specific interactions between the two mesogenic groups do lead to a significant variation in the mesophase behaviour of such materials.…”

Section: Introductionmentioning

confidence: 99%

The effect of inversion of the ester group on the mesophase behaviour of some azo/ester compounds

et al. 2015

View full text Add to dashboard Cite

Five homologous series of 4-substituted phenyl 4′-(4″-alkoxy phenylazo) benzoates (In a-−e ) were prepared in which, within each homologous series, the length of the terminal alkoxy group varies between 8, 10, 12, 14 and 16 carbons, while the other terminal substituent, X, is a polar group that alternatively changed from CH 3 O, CH 3 , H, Br, and CN groups. Compounds prepared were characterised by infrared, mass, and H 1 -NMR spectroscopy and their mesophase behaviour investigated by differential scanning calorimetry (DSC) and polarised light microscopy (PLM). The results were discussed in terms of mesomeric and polarisability effects. Only for the lower group of compounds, I8 a-e , that showed a nematic phase, the nematic-to-isotropic transition temperatures (T N-I ) were successfully correlated to the polarisability anisotropy of bonds to the substituent X. A comparative study was made between the investigated compounds and two previously prepared isomeric groups. In the first group of isomers, 4-(4′alkoxy phenylazo) phenyl 4″-substituted benzoates (IIn a-e ), the ester groups are inverted. While in the second, 4-(4′-substituted phenylazo) phenyl 4″-alkoxy benzoates (IIIn a-e ), two modifications were made, inversion of the COO group, and exchange of the two wing substituents Keywords: phenylazo phenyl benzoates; mesophase behaviour; inversion of ester group; polarisability anisotropy

show abstract

Section: Introductionmentioning

confidence: 99%

The effect of inversion of the ester group on the mesophase behaviour of some azo/ester compounds

et al. 2015

View full text Add to dashboard Cite

show abstract

“…[6][7][8] Particularly, LC heterocycles have ability to impart lateral or longitudinal dipole combined with changes in molecular shapes. [9,10] Oxazepines are class of compounds which belong to seven-membered heterocyclic family possessing the nitrogen and oxygen hetero atoms. 1,3-Oxazepine derivatives play an important role in medicinal chemistry since the positions of oxygen and nitrogen in the ring changes the properties of the molecules.…”

Section: Introductionmentioning

confidence: 99%

Novel oxazepinedione-derived symmetric dimers: synthesis and mesophase characterisation of seven-membered heterocyclic compounds

et al. 2016

View full text Add to dashboard Cite

The synthesis and characterisation of three sets of symmetric dimeric compounds composed of seven-membered oxazepinedione heterocyclic rings were carried out. All the dimers possess the tetradecyl-(n = 14) alkyl side chain attached to the nitrogen atom of the oxazepinedione core. The oxazepinedione core in turn was connected with varied connecting spacers (n = 4, 6, 8, 10 and 12). The dimers were spectroscopically characterised by FT-IR, 1 H-NMR, 13 C-NMR and elemental analysis techniques. The compounds were investigated for liquid crystalline properties using differential scanning calorimetry and polarising optical microscopy with heating assembly. The precursor imines 2a-e itself started exhibiting liquid crystalline SmA/tilted hexatic mesophase. Further fusion of 2a-e with maleic anhydride, succinic anhydride and phthalic anhydride gave the novel oxazepinedione-derived symmetric dimers 3a-e, 4a-e and 5a-e respectively. The dimers 3a-e and 4a-e did not exhibit any liquid crystal (LC) properties. However, the phthalic anhydride-fused oxazepinediones 5a-e show monotropic nematic liquid crystalline phase. The results indicate that the formation of mesophase is dependent on the type of fused oxazepinedione ring. ARTICLE HISTORY

show abstract

“…LC dimers may be divided into two broad classes: symmetric [10,37,42] and nonsymmetric. [21,23,24,[29][30][31][32][33][34][35]42,43] In a symmetric LC dimer, the two mesogenic units are identical, whereas they are different in a non-symmetric dimer.…”

Section: Introductionmentioning

confidence: 99%

“…LC dimers have now attracted considerable research interest over a prolonged period, [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] not only because they can be used as models of thermotropic, semi-flexible main chain liquid crystalline, but also because of their quite different behaviours to conventional low-molar-mass LCs. LC dimers may be divided into two broad classes: symmetric [10,37,42] and nonsymmetric.…”

Section: Introductionmentioning

confidence: 99%

1,2-Propanediol-linked chiral symmetric and non-symmetric liquid crystal dimers containing trifluoromethyl

Yao

Feng

et al. 2016

Liquid Crystals

View full text Add to dashboard Cite

2016): 1,2-Propanediol-linked chiral symmetric and nonsymmetric liquid crystal dimers containing trifluoromethyl, Liquid Crystals, ABSTRACT Four symmetric and non-symmetric chiral liquid crystal dimers containing trifluoromethyl groups, termed as TFBA-PD-TFBA, UEBBA-PD-TFBA, UEBA-PD-TFBA and UEA-PD-TFBA, respectively, have been synthesised and characterised. UEA-PD-TFBA exhibited chiral nematic phase, whereas the other three dimers displayed chiral smectic A phase. X-ray diffraction (XRD) has revealed the structure of the smectic A phase for TFBA-PD-TFBA to be intercalated, whereas that for UEBBA-PD-TFBA and UEBA-PD-TFBA to be monolayer and interdigitated, respectively. In addition, the weaker peak corresponding to a shorter layer spacing was observed for UEBBA-PD-TFBA and UEBA-PD-TFBA. Considering the results of XRD measurements and computer simulations, the structural model corresponding to the shorter layer spacing is assigned as horseshoe-like shape. The absence of smectic behaviour for UEA-PD-TFBA reveals that the weaker aromatic-aromatic interactions cannot stabilise the smectic A phase. ARTICLE HISTORY

show abstract

Liquid crystal dimers and the twist-bend nematic phase. The preparation and characterisation of the α,ω-bis(4-cyanobiphenyl-4′-yl) alkanedioates

Cited by 87 publications

References 78 publications

The effect of inversion of the ester group on the mesophase behaviour of some azo/ester compounds

The effect of inversion of the ester group on the mesophase behaviour of some azo/ester compounds

Novel oxazepinedione-derived symmetric dimers: synthesis and mesophase characterisation of seven-membered heterocyclic compounds

1,2-Propanediol-linked chiral symmetric and non-symmetric liquid crystal dimers containing trifluoromethyl

Contact Info

Product

Resources

About