Molecular Ordering and Dynamics in the Columnar Mesophase of a New Dimeric Discotic Liquid Crystal As Studied by X-ray Diffraction and Deuterium NMR

Zamir, S.; Poupko, Raphy; Luz, Z.; Hüser, Bernhard; Boeffel, Christine; Zimmermann, Herbert

doi:10.1021/ja00084a042

Cited by 63 publications

(48 citation statements)

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“…A powder sample of ring-deuterated HAT5a-d 6 was studied by an angle-dependent DNMR study [137]. simulate these powder spectra using the threefold jump diffusion model, one needs to calculate the FID, using the following ν(ϕ) for the site labeled by ϕ [138]:…”

Section: Diffusive Motions In Liquid Crystalsmentioning

confidence: 99%

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Recent NMR Studies of Thermotropic Liquid Crystals

Dong¹

2016

Annual Reports on NMR Spectroscopy

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Section: Diffusive Motions In Liquid Crystalsmentioning

confidence: 99%

“…At 9.4 T, this discotic dimer could not be aligned by the NMR field, but its DNMR solid echo intensity versus the pulse separation τ curve at 296 K was analyzed [139], by following the theoretical model described in Ref. [138]. Line shape simulation of the powder spectrum at this temperature was also carried out.…”

Section: Diffusive Motions In Liquid Crystalsmentioning

confidence: 99%

Recent NMR Studies of Thermotropic Liquid Crystals

Dong¹

2016

Annual Reports on NMR Spectroscopy

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“…Dynamics of discotic liquid crystals have drawn attention as well [16,23,24,25,26,27,28,29,30]. The focus has often been on the dynamics of the columnar phase [24,26,28,29,30].…”

Section: Introductionmentioning

confidence: 99%

Orientational relaxation in a discotic liquid crystal

2007

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We investigate orientational relaxation of a model discotic liquid crystal, consisting of disclike molecules, by molecular dynamics simulations along two isobars starting from the high temperature isotropic phase. The two isobars have been so chosen that (a) the phase sequence isotropic- (I-) nematic- (N-) columnar (C) appears upon cooling along one of them and (b) the sequence isotropic- (I-) columnar- (C) along the other. While the orientational relaxation in the isotropic phase near the I-N phase transition in system (a) shows a power law decay at short to intermediate times, such power law relaxation is not observed in the isotropic phase near the I-C phase boundary in system (b). In order to understand this difference (the existence or the absence of the power law decay), we calculated the growth of the orientational pair distribution functions (OPDFs) near the I-N phase boundary and also near the I-C phase boundary. We find that the OPDF shows a marked growth in long range correlation as the I-N phase boundary is approached in the I-N-C system (a), but such a growth is absent in the I-C system, which appears to be consistent with the result that I-N phase transition in the former is weakly first order while the I-C phase transition in the latter is not weak. As the system settles into the nematic phase, the decay of the single-particle second-rank orientational time correlation function follows a pattern that is similar to what is observed with calamitic liquid crystals and supercooled molecular liquids.

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“…Thus, the dimers show more ordered and stable Col mesophase and improved semiconductor properties than triphenylene DLC monomers. Furthermore, triphenylene DLC dimers can form glass Col ho phase in cooling [7,[25][26][27][28][29][30] . Reducing molecular symmetry of triphenylene dimers, such as connecting two different triphenylene mesogens via a spacer or adding amide group into unsymmetrical position of the spacer, can slow down the process of crystallization and result in glass Col phase formation [31] .…”

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Synthesis and mesomorphism of diacetylene-bridged triphenylene discotic liquid crystal dimers

Zhao

et al. 2009

Sci. China Ser. B-Chem.

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m -C≡≡ C-] 2 , 8(m), (m = 1, 3) by Eglinton coupling reaction. The thermotropic liquid crystal properties were studied by differential scanning calorimetry and polarized optical microscopy. The results are showed as follows: the length of peripheral alkyl chains of triphenylene influenced properties of liquid crystal dimers; dimers 3(n) (n = 5-8) and 6 had glass columnar phase, and no crystallization was observed above −50℃ for all the triphenylene dimers; compared with 3(6), 6 showed higher molecular symmetry, more stable columnar mesophase and wider mesophase range. The connecting group, length and rigidity of spacer had important influence on the mesomorphism of diacetylene-bridged triphenylene discotic liquid crystal dimers.triphenylene, discotic liquid crystal, Eglinton coupling reaction, liquid crystal dimer, glass columnar phase Liquid crystal dimers are a type of molecule which contain two identical or different mesogenic groups linked via a spacer. Their physical properties are different from those of conventional low molecular mass liquid crystals. They show a variety of mesophases [1][2][3][4][5][6] and some of liquid crystal dimers display properties of polymers, such as glass transition behavior [7][8][9] . So they can serve as ideal model compounds in liquid crystal polymer investigation and have received considerable attention. Rod-like liquid crystal dimers have been well studied and their structure-property relationships have been elucidated [10] . By contrast, discotic liquid crystals (DLCs) have comparatively short history. Thus, further exploration of the synthesis, characterization and structure-property relationships of DLC dimers, oligomers and polymers is necessary.Triphenylene derivatives are important family members of DLCs. They can self-assemble into highly ordered hexagonal columnar (Col ho ) mesophase and possess high mobility of charges and energy [11] . Moreover, triphenylene DLCs can be easily synthesized and purified, showing plenty of structural variation and fine thermal and chemical stability [12,13] . They have been applied as one-dimensional conductors [14] , photoconductors [15] , and light-emitting diodes [16] . In recent years, triphenylene DLC dimers, oligomers and polymers have attracted increasing attention [17][18][19][20][21][22][23][24] . The dynamics of discogens, such as rotation around the column axes, fluctuation in the column, and slippage out of column, has been partially inhibited by connecting two triphenylene mesogens via a spacer. Thus, the dimers show more ordered and stable Col mesophase and im-

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Molecular Ordering and Dynamics in the Columnar Mesophase of a New Dimeric Discotic Liquid Crystal As Studied by X-ray Diffraction and Deuterium NMR

Cited by 63 publications

References 0 publications

Recent NMR Studies of Thermotropic Liquid Crystals

Recent NMR Studies of Thermotropic Liquid Crystals

Orientational relaxation in a discotic liquid crystal

Synthesis and mesomorphism of diacetylene-bridged triphenylene discotic liquid crystal dimers

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