Advances in Liquid Crystal Dimers and Oligomers

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Liquid Crystals".

Deadline for manuscript submissions: 10 June 2025 | Viewed by 3875

Special Issue Editors


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Guest Editor
Departament de Física, Universitat Politècnica de Catalunya, Campus Nord B4-B5, E-08034 Barcelona, Spain
Interests: liquid crystals; disordered systems; thermodynamics; dielectrics; glass transition

E-Mail Website
Guest Editor
Departament de Física, Universitat Politècnica de Catalunya, Campus Nord B4-B5, E-08034 Barcelona, Spain
Interests: polymers, disordered systems; dielectrics; conductivity; glass transition

Special Issue Information

Dear Colleagues,

Liquid crystal dimers and oligomers were originally synthesized in the 1980s as the fundamental units used to study the chemistry and physics of LC polymers. This new approach enabled our understanding of some interesting properties, such as the odd–even effect in transition temperatures and entropies or the nature and behavior of dielectric relaxation modes, among others. Three decades later, the novel twist–bend nematic mesophase was experimentally discovered, opening a new field in research into LC materials, which is still a hot topic.

This Special Issue aims to address the recent advances in LC dimers and oligomers, from design and synthesis, passing through theory, simulation, and physical characterization to technological applications of such materials.

Dr. Sergio Diez Berart
Prof. Dr. Jordi Sellarés
Guest Editors

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Keywords

  • liquid crystal (LC) dimers
  • LC oligomers
  • design
  • synthesis
  • simulations
  • theory
  • physical characterization
  • twist-bend nematic
  • applications

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Published Papers (2 papers)

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Research

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16 pages, 5087 KiB  
Article
Cyanobiphenyl- and Cyanoterphenyl-Based Liquid Crystal Dimers (CBnCT): The Enantiotropic Twist-Bend Nematic Phase
by Yamato Shimoura and Yuki Arakawa
Crystals 2025, 15(2), 120; https://doi.org/10.3390/cryst15020120 - 23 Jan 2025
Cited by 1 | Viewed by 1151
Abstract
We report the first homologous series of methylene-linked cyanobiphenyl- and cyanoterphenyl-based liquid crystal (LC) dimers (CBnCT). To induce the heliconical twist-bend nematic (NTB) phase through bent molecular shapes, the CBnCT homologs have an odd-numbered flexible alkylene spacer [...] Read more.
We report the first homologous series of methylene-linked cyanobiphenyl- and cyanoterphenyl-based liquid crystal (LC) dimers (CBnCT). To induce the heliconical twist-bend nematic (NTB) phase through bent molecular shapes, the CBnCT homologs have an odd-numbered flexible alkylene spacer (n) ranging from 1 to 17. Polarized optical microscopy and differential scanning calorimetry are used to identify phases and analyze the phase-transition behavior. Except for n = 1, all the CBnCT homologs exhibit the conventional nematic (N) and NTB phases. The CBnCT dimers with n = 3 and 5 show a monotropic NTB phase, while those with n = 7, 9, 11, 13, 15, and 17 demonstrate an enantiotropic NTB phase below the conventional N phase temperature. The NTB phases of the CBnCT dimers (n = 7, 9, and 11) remain stable down to room temperature and vitrify without crystallization. Compared with cyanobiphenyl-based LC dimer homologs (CBnCB), the CBnCT dimers show significantly broader N and NTB phase temperature ranges with higher isotropic and NTB–N phase-transition temperatures. The NTB phase temperature ranges of CBnCT (n = 7, 9, 11, and 13) are over 100 °C. Additionally, more CBnCT homologs exhibit the enantiotropic NTB phase than the CBnCB ones. These enhancements result from increased π-conjugation and asymmetric molecular structures. Furthermore, CB9CT exhibits higher birefringence than CB9CB owing to its longer π-conjugated terphenyl moiety. Full article
(This article belongs to the Special Issue Advances in Liquid Crystal Dimers and Oligomers)
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Review

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29 pages, 18161 KiB  
Review
Liquid-Crystalline Supermolecules Inducing Layer Fluctuations: From Hierarchical to Dissipative Structures
by Atsushi Yoshizawa
Crystals 2024, 14(8), 681; https://doi.org/10.3390/cryst14080681 - 26 Jul 2024
Cited by 1 | Viewed by 2075
Abstract
Liquid crystals, which have both liquid and solid properties, inevitably exhibit fluctuations. Some frustrated liquid-crystalline phases with a hierarchical structure, such as cybotactic nematic, modulated smectic, and bicontinuous cubic phases, are fascinating fluctuation-induced phases. In addition to these equilibrium phases, a pattern formation [...] Read more.
Liquid crystals, which have both liquid and solid properties, inevitably exhibit fluctuations. Some frustrated liquid-crystalline phases with a hierarchical structure, such as cybotactic nematic, modulated smectic, and bicontinuous cubic phases, are fascinating fluctuation-induced phases. In addition to these equilibrium phases, a pattern formation that is a nonequilibrium order through fluctuation is one of the most attractive research areas in soft matter. In this review, the studies on producing these fluctuation-induced orders in liquid crystals are described. Liquid-crystalline supermolecules in which several mesogens are connected via a flexible spacer have been designed. They have not only a characteristic shape but also an intra-molecular dynamic order. The supermolecules induce the fluctuations in layer structures at a molecular level, producing from the frustrated hierarchical to dynamic dissipative structures. In addition to reviewing molecular design for the hierarchical structures, the pattern propagation in a smectic phase is discussed based on the rotation of smectic blocks through Rayleigh–Bénard convection. Full article
(This article belongs to the Special Issue Advances in Liquid Crystal Dimers and Oligomers)
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