Splay Nematic Phase

Mertelj, Alenka; Cmok, Luka; Sebastián, Nerea; Mandle, Richard J.; Parker, Rachel R.; Whitwood, Adrian C.; Goodby, John W.; Čopič, Martin

doi:10.1103/physrevx.8.041025

Cited by 152 publications

(218 citation statements)

References 33 publications

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“…In the isotropic phase (I), a single relaxation process (miso) is detected with frequency of the order of 20 MHz for the rigid dipolar molecule rotating in the isotropic environment. iso17 is in agreement with the large calculated molecular longitudinal dipole moment ~11.4 D [10]. In the N phase, immediately after the I-N transition and in the frequency range studied, a single process ||,1 m is detected with lower frequency and larger amplitude than in the I phase.…”

Section: Subject Areas: Soft Matter Materials Science Phase Transitsupporting

confidence: 88%

“…In the N phase, SHG image appears completely dark, as expected for a homogeneously oriented non-polar nematic liquid crystal (Fig 2(a)). On cooling, the transition to the splay phase is characterized by a sudden strong SHG signal (coinciding with the destabilization of homogeneous orientation observed by polarization microscopy (POM) [10]). During the transition, the SHG image clearly shows a periodic stripped texture (Fig 2(b)) with a periodicity of around FERROELECTRIC-FERROELASTIC PHASE TRANSITION 8 to 9 μm perpendicular to the rubbing direction.…”

Section: Subject Areas: Soft Matter Materials Science Phase Transitmentioning

confidence: 78%

“…The so called splay nematic phase was just recently discovered [10,11] to appear in materials made of molecules with a large dipole moment and a lateral group, which results in a slightly wedge molecular shape ( Fig.1a) [12,13]. These materials exhibit two distinct nematic mesophases, the usual uniaxial nematic phase and the lower temperature splay nematic phase.…”

Section: Subject Areas: Soft Matter Materials Science Phase Transitmentioning

confidence: 99%

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Ferroelectric-Ferroelastic Phase Transition in a Nematic Liquid Crystal

et al. 2020

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Ferroelectric ordering in liquids is a fundamental question of physics. Here, we show that ferroelectric ordering of the molecules causes formation of recently reported splay nematic liquidcrystalline phase. As shown by dielectric spectroscopy, the transition between the uniaxial and the splay nematic phase has the characteristics of a ferroelectric phase transition, which drives an orientational ferroelastic transition via flexoelectric coupling. The polarity of the splay phase was proven by second harmonic generation (SHG) imaging, which additionally allowed for determination of the splay modulation period to be of the order of 5 -10 microns, also confirmed by polarized optical microscopy. The observations can be quantitatively described by a Landau-de Gennes type of macroscopic theory. SI A. Material RM734 was synthesized according to Ref.[1] and additionally purified as described in Ref. [2]. As determined by means of differential scanning calorimetry phase transition temperatures have been determined to be: isotropic to nematic TIN= 187.9 °C, nematic to second nematic transition at TNNs = 132.7 °C, and a melting point at Tm = 139.8 °C. We used the Gaussian G09e01 suite of programs [3] to determine the B3LYP/6-31G(d) minimized geometry of RM734 shown in Fig.1. The molecular dipole moment calculated by the B3LYP/6-31G(d) level of DFT is of 11.3748D and oriented almost along the molecular long axis.

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Section: Subject Areas: Soft Matter Materials Science Phase Transitsupporting

confidence: 88%

Section: Subject Areas: Soft Matter Materials Science Phase Transitmentioning

confidence: 78%

Section: Subject Areas: Soft Matter Materials Science Phase Transitmentioning

confidence: 99%

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Ferroelectric-Ferroelastic Phase Transition in a Nematic Liquid Crystal

et al. 2020

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“…experimentally demonstrated the electrically induced splay–bend nematic (N SB ) phase transition from the N TB phase for a bent‐core molecule and the bent‐shaped dimer CB7CB . While the local director modulation of the N SB phase is oriented parallel to the average N director direction, that of the splay N (N S ) phase was found to be perpendicular to the average N‐director direction . The mechanisms of formation of the N SB and N S phases were comprehensively explained …”

Section: Introductionmentioning

confidence: 96%

Ether‐ and Thioether‐Linked Naphthalene‐Based Liquid‐Crystal Dimers: Influence of Chalcogen Linkage and Mesogenic‐Arm Symmetry on the Incidence and Stability of the Twist–Bend Nematic Phase

Arakawa

Ishida

Tsuji

2020

Chemistry A European J

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The twist–bend nematic (NTB) phase with a heliconical nanostructure of the local director generating symmetry breaking by achiral bent‐shaped molecules is a hot topic of current liquid‐crystal science. As opposed to the most common methylene‐linked dimers, this study demonstrates chalcogen ether‐ and/or thioether‐linked 6‐(4‐cyanophenyl)‐2‐naphthyl‐based liquid‐crystal dimers with symmetric and asymmetric π‐conjugated mesogenic‐arm structures that exhibit the NTB phase. Although the symmetric bis(ether)‐linked dimer exhibits only the conventional nematic (N) phase, the asymmetric bis(ether)‐linked dimer can form the NTB phase. All thioether‐linked dimers form the NTB phase, wherein the dimers with asymmetric arms vitrify in the NTB phase on cooling to room temperature. The phase transitions are discussed in terms of the chalcogen linkage combination, mesogenic‐arm symmetry, and spacer length. It is revealed that thioether‐linked dimers based on asymmetric π‐conjugated mesogenic arms with terminal cyano groups are highly beneficial for the realization of materials that form a wide range of NTB phases and glassy NTB states at room temperature.

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“…Other modulated nematic‐like phases are known to exist: Mertelj et al. recently discovered a nematic‐like mesophase with a periodic splay modulated structure (N S ), and we recently reported a novel nematic‐like phase in binary mixtures of bent‐dimers and a high helical twisting power additive …”

Section: Introductionmentioning

confidence: 90%

Pentaerythritol Derived Tetrapode Exhibiting a Nematic‐Like Mesophase at Ambient Temperatures

Hann

Mandle

2019

ChemPhysChem

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The nematic liquid‐crystalline phase exhibits average orientational order, with no positional organisation. So‐called modulated nematic phases exhibit this same orientational order with an additional spatially periodic modulation of the nematic director, the most common of which is the twist‐bend nematic phase. We report a pentaerythritol derived tetrapode which exhibits a nematic‐like mesophase at ambient temperature, and we denote this new mesophase ‘NX’ to indicate a nematic phase of unknown structure. X‐ray scattering experiments refute the possibility of positional order, yet optical textures are consistent with a periodic structure. We suggest that the mesophase exhibited by this material is a new type of nematic‐like mesophase with some form of modulated structure. We find the NX phase to exhibit an electrooptic response consistent with a nematic‐like phase.

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Splay Nematic Phase

Cited by 152 publications

References 33 publications

Ferroelectric-Ferroelastic Phase Transition in a Nematic Liquid Crystal

Ferroelectric-Ferroelastic Phase Transition in a Nematic Liquid Crystal

Ether‐ and Thioether‐Linked Naphthalene‐Based Liquid‐Crystal Dimers: Influence of Chalcogen Linkage and Mesogenic‐Arm Symmetry on the Incidence and Stability of the Twist–Bend Nematic Phase

Pentaerythritol Derived Tetrapode Exhibiting a Nematic‐Like Mesophase at Ambient Temperatures

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