Liquid crystal dimers and oligomers

Imrie, Corrie T.; Henderson, Peter A.

doi:10.1016/s1359-0294(02)00092-4

Cited by 280 publications

(134 citation statements)

References 49 publications

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“…Whereas the formation of intercalated arrangement may be driven by the following factors: (1) an electrostatic quadrupolar interaction between the unlike mesogenic groups having quadrupole moments of opposite signs, (2) the increase in entropy gained from the homogeneous mixing of the mesogenic moieties, (3) constraint of spacer filling and (4) the effect of excluded volume. [36] The estimated molecular lengths of UEBA-PD-TFBA and UEBBA-PD-TFBA are different, while maximum layer spacings observed are same. To fit the experimentally observed layer spacings, we proposed the interdigitated structure and monolayer for UEBA-PD-TFBA and UEBBA-PD-TFBA, respectively.…”

Section: Lc Properties Analysismentioning

confidence: 88%

“…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%

“…A key issue in the area of chiral LC dimers was to determine how the form chirality of the chiral phase would depend on the number of methylene groups in the flexible alkyl space. [36,45] Cholesterol, [10,11,43,45] (S)-(-)-2-methyl-1-butanol [34,45] and (S)-(-)-2-methyl-1-enanthol [24] were usually used in chiral dimers. The bifunctional chiral reagents were seldom used in chiral trimers, [7,46] let alone in chiral dimers.…”

Section: Introductionmentioning

confidence: 99%

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

Yao

Feng

et al. 2016

Liquid Crystals

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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

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Section: Lc Properties Analysismentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Yao

Feng

et al. 2016

Liquid Crystals

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“…The mesomorphic behaviour of organic compounds depends on the structure of the molecules and can be varied by modifying its molecular structure including linking, terminal and core groups [4].…”

Section: Introductionmentioning

confidence: 99%

Synthesis and comparative studies of phase transition behaviour of new dimeric liquid crystals consisting of dimethyluracil and biphenyl cores

Mohammad

Srinivasa

et al. 2016

Journal of Molecular Liquids

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A new homologous series of mesogens containing 6-amino-1,3-dimethyluracil moiety have been synthesized. The structures of the compounds were characterised by elemental analysis, FT-IR, 1 H and 13 C NMR spectroscopic techniques. Their mesomorphic properties were studied by polarising optical microscopy attached to a heating stage. Microscopy data were supported with transition temperatures and enthalpy change values obtained from the differential scanning calorimetry analysis. The studies have shown that the mesomorphic properties of the compounds are dependent on the lengths of alkoxy-spacers. Compounds 4a-f with a shorter alkoxyspacer chain (n = 6) exhibited smectic A phase, while compounds 4g-r with a alkoxy-spacer chain (n = 8 or 10) displayed nematic phase.

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“…Schlieren texture being the signature of nematic phase indicates that the liquid crystal phase of OF8T2 is nematic. An enlightening review of the structure-property relationship of linear liquid-crystal oligomers can be found in [9,10].…”

Section: Introductionmentioning

confidence: 99%

Density functional theory of freezing of a system of conjugated oligomers parameterised via Gay–Berne potential

2015

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Density functional theory (DFT) of freezing is used to study the isotropic-nematic, isotropic-smectic A and nematic-smectic A phase transitions in a system of large, semi-flexible conjugated oligomers parameterised within Gay-Berne (GB) potential. The pair correlation functions of the isotropic fluid, used as structural inputs in the DFT, are calculated by solving the Percus-Yevick integral equation theory. Large number of spherical harmonic coefficients of each orientation-dependent functions has been considered to ensure the numerical accuracy at different densities and temperatures for the system of these model GB ellipsoids having large aspect ratio (length-to-breadth ratio). We found that the system of GB ellipsoids parameterised for conjugated oligomers shows stable isotropic, nematic and smectic A phases. At low temperatures, on increasing the density, isotropic fluid makes a direct transition to smectic A phase. Nematic phase get stabilised in between the isotropic and smectic A phases on increasing the temperature. Using the transition parameter obtained through the DFT, we have plotted the temperature-density and pressure-temperature phase diagrams which are found to be qualitatively similar to the one obtained in simulations for the systems with low aspect ratio GB particles.

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Liquid crystal dimers and oligomers

Cited by 280 publications

References 49 publications

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

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

Synthesis and comparative studies of phase transition behaviour of new dimeric liquid crystals consisting of dimethyluracil and biphenyl cores

Density functional theory of freezing of a system of conjugated oligomers parameterised via Gay–Berne potential

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