Synthesis and properties of low-molar-mass liquid-crystalline siloxane derivatives

Newton, JM; Coles, H. J.; Hodge, Philip; Hannington, John

doi:10.1039/jm9940400869

Cited by 82 publications

(48 citation statements)

References 4 publications

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“…[7] A similar result can be obtained for materials when a sterically demanding 'bulky' group, such as pentamethyldisiloxane, is introduced at the terminus of an aliphatic chain. [8][9][10] Recently, a new design feature for the stabilisation of the smectic A phase was identified, which involves the incorporation of a halogen atom, typically Cl or Br, at the terminal position of the peripheral chain of a rod-shaped molecular architecture. [11] This stabilisation effect was first reported in a series of chloro-terminated derivatives of the 4-substituted difluoroterphenyl core system, as exemplified by compounds 1, 2 and 3 in Table 1.…”

Section: Introductionmentioning

confidence: 99%

Liquid-crystalline structure–property relationships in halogen-terminated derivatives of cyanobiphenyl

et al. 2014

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In this article, we report on the liquid-crystalline properties of two series of halogen-terminated cyanobiphenylbased materials. Unlike other rod-shaped, halogen-terminated materials reported, these materials do not exhibit the smectic A phase and instead only exhibit nematic liquid-crystal mesomorphism. Comparisons between these materials and analogous unsubstituted materials were made, and the relationships between their molecular structures and phase behaviour are discussed with the aid of molecular modelling at the B3LYP/6-31G* level of density functional theory.

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Section: Introductionmentioning

confidence: 99%

Liquid-crystalline structure–property relationships in halogen-terminated derivatives of cyanobiphenyl

et al. 2014

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“…Various mesogens have been combined with siloxane-containing linkers and backbones. The most prominent examples are cyano biphenyls, [20,26,28,34] biphenyl benzoates, [25,30,33,36] phenyl benzoates with long alkyl chains, [24,27] and cholesteryl benzoates. [27,[30][31][32] In the early 1990s, Percec et al discovered long alkoxy-substituted gallic acid derivatives as novel mesogens.…”

Section: Introductionmentioning

confidence: 99%

“…[15][16] Apart from studies on polymeric systems, siloxane-containing LMW-LCs received great attention, since they respond faster to external stimuli, and their structural behavior is similar to that of their polymeric analogues. [17][18][19] Various silicon-containing LMW-LC systems were synthesized up to now: oligosiloxane-and oligocarbosilane-terminated monomesogens on the one hand, [20][21][22][23] and bi-, tetra-, and oligomesogens with various siloxane, carbosilane, or silsesquioxane linker groups on the other. [24][25][26] Most attention has been paid to cyclic and linear oligosiloxane linkers.…”

Section: Introductionmentioning

confidence: 99%

Self‐Assembly of Linear and Cyclic Siloxane‐Containing Mesogens: Investigation of Layered Structures in Bulk and Thin Films

et al. 2011

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Silicon-containing materials which possess the ability to form mesophases are promising systems for applications in the fields of electro-optical devices, nonlinear optics, and information storage media. In this work, the formation of supramolecular assemblies of a series of low molecular weight siloxane-containing mesogens is presented. Besides a novel synthesis route via Ru(II) -catalyzed hydrosilylation of phenyl acetylene derivatives, mesophase characterization by modern analysis techniques is performed. As linker groups, leading to bi- and tetramesogens, linear disiloxane and cyclic tetrasiloxane are utilized. In the resulting class of materials, high thermal stability, induced by the formation of layered smectic-type structures, is predominant. The smectic-type phases were found to be monotropic. Layer distances in the assemblies, as well as the phase transition temperatures, can be controlled by the substitution motif on the mesogens (number and length of alkyl chains). In spin-cast thin films, the layered domains are visualized by atomic force microscopy; furthermore, domain dimensions and electron densities are determined by grazing-incidence small-angle X-ray scattering.

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“…However, layer structures of smectic phases are thermodynamically stabilized by the effects of oligosiloxane chain nanosegregation. 30 In de Vries type ferroelectric liquid crystals, a temperature-independent layer spacing of the ferroelectric LC phase has been reported. 31 Only one example of columnar liquid crystals of triphenylene derivatives bearing six oligosiloxane chains has been reported.…”

Section: Nanosegregated Columnar Phases Of Perylene Bisimide Derivatimentioning

confidence: 99%

“…29 Linear oligosiloxane chains, such as 1,1,1,3,3,5,5-heptamethyl-2,4-trisiloxane and 1,1,1,3,3-pentamethyl-2-disiloxane, were introduced to the terminals of the alkyl side chains of rod-like LC molecules. 30 Compared with alkyl chains, which have a tendency to form an all-trans conformation, oligosiloxane chains consist of Si-O bonds with longer bond lengths than C-C bonds and low rotational potentials, resulting in their remarkable thermal motion. However, layer structures of smectic phases are thermodynamically stabilized by the effects of oligosiloxane chain nanosegregation.…”

Section: Nanosegregated Columnar Phases Of Perylene Bisimide Derivatimentioning

confidence: 99%

Integration of electro-active π-conjugated units in nanosegregated liquid-crystalline phases

Funahashi

2016

Polym J

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Unlike conventional liquid crystals bearing alkyl chains, perylene tetracarboxylic bisimide (PTCBI) derivatives bearing oligosiloxane moieties were synthesized. The oligosiloxane moieties are bulky and have a tendency to form a liquid-like conformation due to the low rotation potential of Si-O bonds. The PTCBI derivatives bearing oligosiloxane chains exhibit the columnar phase at room temperature. They are soluble in various organic solvents, and thin films can be produced by a spin-coating method. In the columnar phase, crystal-like π-stacks are surrounded by a liquid-like mantle consisting of the oligosiloxane moieties of the PTCBI derivatives, resulting in efficient electron transport. Even the PTCBI derivatives bearing polymerizable cyclotetrasiloxane rings show the liquid-crystalline (LC) phases at room temperature. The spin-coated films of the LC PTCBI derivatives with cyclotetrasiloxane rings can be polymerized and insolubilized by exposure to the vapors of trifluoromethanesulfonic acid. PTCBI derivatives bearing oligosiloxane moieties and a triethylene oxide chain coordinated to ionic species exhibit a dimeric lamellar phase in which ion-conductive sublayers and electron-transporting π-stacks are separately self-organized. Phenylterthiophene derivatives bearing oligosiloxane moieties show a ferroelectric smectic C* phase in which the anomalous photovoltaic effect is observed.

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Synthesis and properties of low-molar-mass liquid-crystalline siloxane derivatives

Cited by 82 publications

References 4 publications

Liquid-crystalline structure–property relationships in halogen-terminated derivatives of cyanobiphenyl

Liquid-crystalline structure–property relationships in halogen-terminated derivatives of cyanobiphenyl

Self‐Assembly of Linear and Cyclic Siloxane‐Containing Mesogens: Investigation of Layered Structures in Bulk and Thin Films

Integration of electro-active π-conjugated units in nanosegregated liquid-crystalline phases

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