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Volumn 13, Issue 9, 2007, Pages 2556-2577

Layer frustration, polar order and chirality in liquid crystalline phases of silyl-terminated achiral bent-core molecules

Author keywords

Ferroelectricity; Liquid crystals; Mesophases; Self assembly; Supramolecular chemistry

Indexed keywords

CHIRALITY; FERROELECTRICITY; PARAFFINS; SELF ASSEMBLY; SMECTIC LIQUID CRYSTALS;

EID: 34250695041     PISSN: 09476539     EISSN: 15213765     Source Type: Journal    
DOI: 10.1002/chem.200600876     Document Type: Article
Times cited : (56)

References (118)
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    • [*]. see D. M. Walba, L. Eshdat, E. Körblova, R. K. Shoemaker, Cryst. Growth Des. 2005, 5, 2091-2099. and references given in [30].
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    • [*] phases: a G. Heppke, D. D. Parghi, H. Sawade, Liq. Cryst. 2000, 27, 313-320;
    • [*] phases: a) G. Heppke, D. D. Parghi, H. Sawade, Liq. Cryst. 2000, 27, 313-320;
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    • However, the molecular length (l = 5.6nm. determined as described in footnote [c] in Table 1) is significantly larger than the parameter b) and this is quite unusual in this case. A possible explanation could be that the molecules are not strictly orthogonal arranged within the ribbons, but adopt a tilled organization where the tilt direction changes randomly along the direction c. It is also possible that there is some intercalation of the terminally unsaturated chains which leads to a reduction of the efficient molecular length.
    • However, the molecular length (l = 5.6nm. determined as described in footnote [c] in Table 1) is significantly larger than the parameter b) and this is quite unusual in this case. A possible explanation could be that the molecules are not strictly orthogonal arranged within the ribbons, but adopt a tilled organization where the tilt direction changes randomly along the direction c. It is also possible that there is some intercalation of the terminally unsaturated chains which leads to a reduction of the efficient molecular length.
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    • Re-indexation with improved X-ray data gave an oblique lattice with smaller lattice parameters than reported in a previous communication ref, 16
    • Re-indexation with improved X-ray data gave an oblique lattice with smaller lattice parameters than reported in a previous communication (ref. [16])
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    • The fact that only one diffuse scattering is found for the carhosilane Sil does not necessarily mean that in this ease the Si-containing units are not segregated. The ethyldimethylsilyl groups (and also the carbosilane units in CSi3) provide the same mean distance as the alkyl chains. For this reason in the case of the investigated carbosilancs. the presence of a segregated structure cannot be deduced from the profile of the wide angle scattering.[19h
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    • [*] phases: T. Sekine, T. Niori, J. Watanabe, T. Furukawa, S. W. Choi, H. Takezoe, J. Mater. Chem. 1997, 7, 1307-1309;
    • [*] phases: T. Sekine, T. Niori, J. Watanabe, T. Furukawa, S. W. Choi, H. Takezoe, J. Mater. Chem. 1997, 7, 1307-1309;
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    • -1(1/cosθ).
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    • Remarkably, also the birefringent textures obtained after shearing have a significantly lower viscosity than the original dark conglomerate phases of compounds Si1 and Si2.
    • Remarkably, also the birefringent textures obtained after shearing have a significantly lower viscosity than the original dark conglomerate phases of compounds Si1 and Si2.
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    • In a previous paper see ref, 19f, we have supported this proposal by the observation of a tilt-angle dependent inversion of the optical rotation, which is proposed by this model
    • In a previous paper (see ref. [19f]) we have supported this proposal by the observation of a tilt-angle dependent inversion of the optical rotation, which is proposed by this model.
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    • In polyimide-coatcd cells the switching behavior can be more complex in some cases, due to the effect of an induced electric double layer, which will be discussed in section on the influence of surfaces
    • In polyimide-coatcd cells the switching behavior can be more complex in some cases, due to the effect of an induced electric double layer, which will be discussed in section on the influence of surfaces.
  • 91
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    • In this notation the structure of the layer stacks is given in brackets and the following subscripts define the correlation between the layer stacks a, anticlinic, s, synclinic, A, antipolar, S, synpolar
    • In this notation the structure of the layer stacks is given in brackets and the following subscripts define the correlation between the layer stacks (a = anticlinic, s = synclinic, A = antipolar, S = synpolar).
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    • This kind of field induced texture was observed earlier in an AF switching smectic phase SmCPA, M. Zennyoji, Y. Takanishi, K. Ishikawa, J. Thisayukta, J. Watanabe, H. Takezoe, J. Maler. Chem. 1999, 9, 2775-2778
    • A): M. Zennyoji, Y. Takanishi, K. Ishikawa, J. Thisayukta, J. Watanabe, H. Takezoe, J. Maler. Chem. 1999, 9, 2775-2778.
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    • The symbol E, according to the rules used by Beilstein, replaces stercochemical descriptors, in cases of configurational uncertainty and inhomogenity. see Stereochemical descriptors in Beilstein Handbook of Organic Chemistry, 18. Part 1, 4th ed., 5th Suppl., Springer, Berlin, 1986, p. LXXV.
    • The symbol E, according to the rules used by Beilstein, replaces stercochemical descriptors, in cases of configurational uncertainty and inhomogenity. see Stereochemical descriptors in Beilstein Handbook of Organic Chemistry, Vol 18. Part 1, 4th ed., 5th Suppl., Springer, Berlin, 1986, p. LXXV.
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    • The relaxation time decreases with increasing frequency of the applied AC field. The relaxation is very slow (i.e., it takes some minutes for completion) if the sample is aligned in a low frequency triangular wave field (10 Hz) and it becomes faster (several seconds) if the frequency is higher (100-500 Hz).
    • The relaxation time decreases with increasing frequency of the applied AC field. The relaxation is very slow (i.e., it takes some minutes for completion) if the sample is aligned in a low frequency triangular wave field (10 Hz) and it becomes faster (several seconds) if the frequency is higher (100-500 Hz).
  • 97
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    • Such a zero voltage centered single peak switching was initially assigned to a superparaelectric switching process where macroscopic FE domains orient under the influence of the field, but are random without applied field: see reference [38, The slow relaxation of the polar states to the dark texture can be regarded as such a type of reorganization. The dependence of the position of the peaks on the type of ITO-cell would mean that the fast switching process changes from FE in noncoaled cells to superparaelectric in polyimide-coated cells. This is however in contradiction with the optical investigations, which indicate that in the polyimide coated cells, where a centered peak is observed, the birefringent texture is retained, whereas the (slow) relaxation to the random organization of the FE domains lakes place in the noneoated ITO cells where a noncentered peak is observed. This makes an explanation of the peak position based on the effect of the internal (effective) field more reaso
    • Such a zero voltage centered single peak switching was initially assigned to a superparaelectric switching process where macroscopic FE domains orient under the influence of the field, but are random without applied field: see reference [38]. The slow relaxation of the polar states to the dark texture can be regarded as such a type of reorganization. The dependence of the position of the peaks on the type of ITO-cell would mean that the fast switching process changes from FE in noncoaled cells to superparaelectric in polyimide-coated cells. This is however in contradiction with the optical investigations, which indicate that in the polyimide coated cells, where a centered peak is observed, the birefringent texture is retained, whereas the (slow) relaxation to the random organization of the FE domains lakes place in the noneoated ITO cells where a noncentered peak is observed. This makes an explanation of the peak position based on the effect of the internal (effective) field more reasonable.
  • 99
    • 34250759942 scopus 로고    scopus 로고
    • A was observed in X-ray experiments. Probably, the stronger surface interactions in the thin measurement cells (5-10 μm) used for the optical and electrooptical investigation provide a strong influence of these surfaces, which seems to stabilize the columnar organization. In X-ray diffraction experiments capillaries (Guinier method) or open droplets (2D X-ray) were used where the influence of the surfaces is diminished.
    • A was observed in X-ray experiments. Probably, the stronger surface interactions in the thin measurement cells (5-10 μm) used for the optical and electrooptical investigation provide a strong influence of these surfaces, which seems to stabilize the columnar organization. In X-ray diffraction experiments capillaries (Guinier method) or open droplets (2D X-ray) were used where the influence of the surfaces is diminished.
  • 101
    • 34250699627 scopus 로고    scopus 로고
    • In polyimide coated ITO cells with the same thickness the transition was found at 126°C, indicating for this compound a significant influence of the surfaces on this phase transition.
    • In polyimide coated ITO cells with the same thickness the transition was found at 126°C, indicating for this compound a significant influence of the surfaces on this phase transition.
  • 105
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    • [19f]
    • [19f]
  • 108
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    • A layer stacks might also be possible for other materials.
    • A layer stacks might also be possible for other materials.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.