Chemical Structure and Mesogenic Properties

Demus, D.; Goodby, John W.; Gray, G. W.; Spieß, Hans Wolfgang; Vill, V.

doi:10.1002/9783527620760.ch6

Cited by 39 publications

(12 citation statements)

References 313 publications

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“…Results presented in Table 1 are in agreement with general trends [ 47 – 48 ] and demonstrate that the replacement of –OCH 2 – with –OOC– increases T NI , while replacement with –CH 2 CH 2 – or –COO– decreases T NI . Overall, the effectiveness of the connecting group in mesophase stabilization follows the order: –OOC(Alk) > –OCH 2 (Alk) > –COO(Alk) > –CH 2 CH 2 (Alk).…”

Section: Discussionsupporting

confidence: 88%

Ring-alkyl connecting group effect on mesogenic properties of p-carborane derivatives and their hydrocarbon analogues

Jankowiak¹,

Kaszyński²,

Tilford³

et al. 2009

Beilstein J. Org. Chem.

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SummaryThe effect of the phenyl–alkyl connecting group on mesogenic properties of several series of isostructural compounds containing p-carborane (A and B), bicyclo[2.2.2]octane (C), and benzene (D) was investigated using thermal and optical methods. Results demonstrated that mesophase stability in the series containing A–D follows the order (Alk)CH2CH2– < (Alk)OOC– < (Alk)CH2O– < (Alk)COO–. Surprisingly, the connecting groups (Alk)CH2CH2– and (Alk)OOC– destabilize the mesophase significantly stronger for carboranes (A and B) than for carbocyclic derivatives (C and D). Analysis indicates that this effect may have quadrupolar and conformational origin.

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Section: Discussionsupporting

confidence: 88%

Ring-alkyl connecting group effect on mesogenic properties of p-carborane derivatives and their hydrocarbon analogues

Jankowiak¹,

Kaszyński²,

Tilford³

et al. 2009

Beilstein J. Org. Chem.

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“…The most obvious difference is that exchange of the alkoxy groups for alkyl groups depresses the clearing points for side chains of equal length (by 67−96 °C), as would be expected on the basis of structure−property trends in calamitic liquid crystals. 1 More importantly, while the alkoxy-substituted DBN(OC n ) compounds give, for the higher (decyloxy and dodecyloxy) homologues, the tilted SmC phase, the alkylsubstituted DBN(C n ) give only untilted SmA and SmB phases. This difference is consistent with the idea that alkoxy groups are more likely to give tilted smectic phases because of the torque introduced by "outboard dipoles" attached to the core.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Molecular shape anisotropy is among the most important criteria in the design of new liquid crystals. 1 The best examples of this are rod-like (calamitic) and disc-like (discotic) compounds, which comprise the great majority of known mesogens. Investigation of other shapes, such as bent core, 2 is an active area of research, with many examples of new and unusual phases.…”

Section: ■ Introductionmentioning

confidence: 99%

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Smectic-A and Hexatic-B Liquid Crystal Phases of Sanidic Alkyl-Substituted Dibenzo[fg,op]naphthacenes

et al. 2016

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Despite longstanding interest in liquid crystalline compounds with simple rod- or disc-like shapes (calamitics or discotics), very few examples of the analogous board-shaped, or "sanidic", liquid crystals exist. A new series of alkyl-substituted dibenzo[fg,op]naphthacenes have been prepared by planarization of o-phenylene precursors through dehydrohalogenation. Their photophysical properties have been studied in dichloromethane. Liquid crystal phase behavior was characterized by polarized optical microscopy, differential scanning calorimetry, and X-ray diffraction. All of the compounds exhibit monotropic liquid crystal phases on cooling from the isotropic phase. The compounds with shorter alkyl (pentyl and heptyl) chains exhibit the uniaxial smectic-A phase analogous to that of simple calamitic mesogens. The compounds with longer alkyl (nonyl, undecyl, and tridecyl) chains exhibit a new smectic liquid crystal phase featuring short-range positional order with an apparent rectangular lattice in the smectic layers, that is, an orthogonal biaxial hexatic-B. The molecular arrangement in this phase likely corresponds to a distorted herringbone packing of the board-shaped structures. Further, the compound with nonyl chains exhibits an underlying smectic-B phase. DFT calculations show that the cores of the mesogens are twisted into C2-symmetric saddle-shaped geometries because of steric interactions along their rims. The liquid crystal phases and their structures are discussed in the context of the compounds' board-like shapes and intercore interactions.

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“…[3] The size, nature and conformation of each molecular segment, as well as the interactions between them, are important parameters to modify when looking for predefined symmetry or properties. For liquid-crystalline dimers it is known that the chemical nature of the central spacer, its length and its parity play an important roll in the final mesomorphic behaviour.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of New Side-Chain Liquid-Crystalline Polyoxetanes with Two Mesogenic Groups Connected by a Flexible Spacer in the Side Chain

Campo¹,

Bello

Pérez

2002

Macromol. Chem. Phys.

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Chemical Structure and Mesogenic Properties

Cited by 39 publications

References 313 publications

Ring-alkyl connecting group effect on mesogenic properties of p-carborane derivatives and their hydrocarbon analogues

Ring-alkyl connecting group effect on mesogenic properties of p-carborane derivatives and their hydrocarbon analogues

Smectic-A and Hexatic-B Liquid Crystal Phases of Sanidic Alkyl-Substituted Dibenzo[fg,op]naphthacenes

Synthesis of New Side-Chain Liquid-Crystalline Polyoxetanes with Two Mesogenic Groups Connected by a Flexible Spacer in the Side Chain

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