Thioether-linked benzylideneaniline-based twist-bend nematic liquid crystal dimers: Insights into spacer lengths, mesogenic arm structures, and linkage types

Arakawa, Yuki; Ishida, Yuko; Komatsu, Kenta; Arai, Yuto; Tsuji, Hideto

doi:10.1016/j.tet.2021.132351

Cited by 13 publications

(4 citation statements)

References 72 publications

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“…Naturally, the N TB phase-transition temperatures (i.e., T INTB or T NNTB ) also showed the same order: ether >> methylene > thioether. This particularly high phase-transition temperature (especially for the LC-Iso or Iso-LC phase transition) with the ether linkage is typical for usual calamitic LCs [69][70][71], including bent LC dimers [28,30,31,33,37,39]. Additionally, CB2SCB is vitrifiable, whereas CB3CB and CB2OCB strongly crystallize.…”

Section: Phase-transition Behaviors Of Cbncb Cbnocb and Cbnscbmentioning

confidence: 85%

Twist–Bend Nematic Phase Behavior of Cyanobiphenyl-Based Dimers with Propane, Ethoxy, and Ethylthio Spacers

et al. 2022

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The twist–bend nematic (NTB) phase is a liquid crystal (LC) phase with a heliconical structure that typically forms below the temperature of the conventional nematic (N) phase. By contrast, the direct transition between the NTB and isotropic (Iso) phases without the intermediation of the N phase rarely occurs. Herein, we demonstrate the effects of linkage type (i.e., methylene, ether, and thioether) on the typical Iso–N–NTB and rare direct Iso–NTB phase-transition behaviors of cyanobiphenyl (CB) dimers CB3CB, CB2OCB, and CB2SCB bearing three-atom-based propane, ethoxy, and ethylthio spacers, respectively. In our previous study, CB2SCB exhibited the monotropic direct Iso–NTB phase transition. In this study, we report that CB3CB also shows the direct Iso–NTB phase transition, whereas CB2OCB exhibits the typical Iso–N–NTB phase sequence with decreasing temperature. The Iso–LC (Iso–NTB or Iso–N) phase-transition temperatures upon cooling show the order CB2OCB (108 °C) > CB3CB (49 °C) > CB2SCB (43 °C). The thioether-linked CB2SCB is vitrifiable, whereas CB3CB and CB2OCB exhibit strong crystallization tendencies. The phase-transition behaviors are also discussed in terms of the three bent homologous series with different oligomethylene spacers n: CBnCB, CBnOCB, and CBnSCB.

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Section: Phase-transition Behaviors Of Cbncb Cbnocb and Cbnscbmentioning

confidence: 85%

Twist–Bend Nematic Phase Behavior of Cyanobiphenyl-Based Dimers with Propane, Ethoxy, and Ethylthio Spacers

et al. 2022

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“…For bent LC dimers, the thioether linkage causes the LC phases to be significantly supercooled and vitrified. This is a consequence of the synergy between the enhanced bent shape of the entire molecule and the flexibility of the C−S−C bond, which prevents crystallization [ 68 , 70 , 71 , 72 , 73 , 74 ]. However, such supercooling effects on LC phases were not observed for the thioether-linked trimers in this study, which all crystallized.…”

Section: Resultsmentioning

confidence: 99%

“…This generally reduces the ability of calamitic molecules to form LCs, by providing greater conformational and steric bulkiness [ 62 , 63 , 64 , 65 , 66 , 67 ]. In contrast, the smaller bond angle of the flexible C–S–C bond synergistically contributes to N TB phase induction and stabilization [ 62 , 63 , 68 , 69 , 70 , 71 , 72 , 73 , 74 ] by enhancing the bent shape and flexibility of LC oligomers with odd- n spacers, as shown in Figure 1 . This is also the case for the higher chalcogen selenoether C–Se–C bond [ 75 ].…”

Section: Introductionmentioning

confidence: 99%

Thioether-Linked Liquid Crystal Trimers: Odd–Even Effects of Spacers and the Influence of Thioether Bonds on Phase Behavior

et al. 2022

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We report the synthesis, phase-transition behavior, and mesophase structures of the first homologous series of thioether-linked liquid crystal (LC) trimers, 4,4′-bis[ω-(4-cyanobiphenyl-4′-ylthio)alkoxy]biphenyls (CBSnOBOnSCB with a wide range of spacer carbon numbers, n = 3–11). All CBSnOBOnSCB homologs exhibited LC phases. Interestingly, even-n and odd-n homologs showed monotropic layered smectic A (SmA) and pseudo-layered twist-bend nematic (NTB) phases, respectively, below a nematic (N) phase. This alternate formation, which depends on spacer chain parity, is attributed to different average molecular shapes, which are associated with the relative orientations of the biphenyl moieties: linear and bent shapes for even-n and odd-n homologs, respectively. In addition, X-ray diffraction analysis indicated a strong cybotactic N phase tendency, with a triply intercalated structure. The phase-transition behavior and LC phase structures of thioether-linked CBSnOBOnSCB were compared with those of the all-ether-linked classic LC trimers CBOnOBOnOCB. Overall, thioether linkages endowed CBSnOBOnSCB with a monotropic LC tendency and lowered phase-transition temperatures, compared to those of CBOnOBOnOCB, for the same n. This is attributed to enhanced flexibility and bending (less molecular anisotropy) of the molecules, caused by the greater bond flexibility and smaller inner bond angles of the C–S–C bonds, compared to those of the C–O–C bonds.

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“…43 Sulfur atoms have been incorporated into the spacer of liquid crystal dimers previously [44][45][46] and used as the link between the spacer and the mesogenic units. [47][48][49][50][51][52][53][54][55][56] The role of the terminal chains in liquid crystal dimers is to exert control, at least to some extent, over the melting point and phase behaviour. It was originally suggested that the inherent flexibility of liquid crystal dimers would inhibit the formation of smectic phases, This was shown, however, not to be the case by Date et al, 57 who reported extensive smectic polymorphism in the family of dimers referred to as m.OnO.m where n is the number of methylene units in the spacer and m the length of the terminal alkyl chains, see Fig.…”

Section: Introductionmentioning

confidence: 99%

The effects of alkylthio chains on the properties of symmetric liquid crystal dimers

et al. 2023

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Thioether-linked benzylideneaniline-based twist-bend nematic liquid crystal dimers: Insights into spacer lengths, mesogenic arm structures, and linkage types

Cited by 13 publications

References 72 publications

Twist–Bend Nematic Phase Behavior of Cyanobiphenyl-Based Dimers with Propane, Ethoxy, and Ethylthio Spacers

Twist–Bend Nematic Phase Behavior of Cyanobiphenyl-Based Dimers with Propane, Ethoxy, and Ethylthio Spacers

Thioether-Linked Liquid Crystal Trimers: Odd–Even Effects of Spacers and the Influence of Thioether Bonds on Phase Behavior

The effects of alkylthio chains on the properties of symmetric liquid crystal dimers

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