A cholesteric liquid crystal device having stable uniform lying helix structure

Yip, W. C.; Welch, Chris; Mehl, Georg H.; Wilkinson, Timothy D.

doi:10.1016/j.molliq.2019.112141

The Effect of Mesogenic Coronas on the Type and Anisotropy of Gold Nanoparticle Superlattices: When Can the Tail Wag the Dog? (2023)
Journal Article
Zhao, Y. Y., Li, Y., Cao, Y., Mehl, G. H., Liu, F., & Ungar, G. (2023). The Effect of Mesogenic Coronas on the Type and Anisotropy of Gold Nanoparticle Superlattices: When Can the Tail Wag the Dog?. Chemistry: a European journal, 29(11), Article e202203673. https://doi.org/10.1002/chem.202203673

The correlation between the size of nanoparticles, the structure and shape of mesogenic ligands and the ensuing assembly behaviour is not really understood. Closer inspection shows very surprising features. Here, 2- and 4-nm gold nanoparticles (NPs)... Read More about The Effect of Mesogenic Coronas on the Type and Anisotropy of Gold Nanoparticle Superlattices: When Can the Tail Wag the Dog?.

Self-assembly of Gold Nanoparticles into an Adjustable Plasmonic 3D Lattice using Janus-type Forked Mesogenic Ligands (2022)
Journal Article
Zhao, Y. Y., Cao, Y., Siligardi, G., Mehl, G. H., Liu, F., & Ungar, G. (2022). Self-assembly of Gold Nanoparticles into an Adjustable Plasmonic 3D Lattice using Janus-type Forked Mesogenic Ligands. Chemistry - An Asian Journal, Article e202200057. https://doi.org/10.1002/asia.202200057

We report the formation of a 3D body-centred self-assembled superlattice of gold nanoparticles whose interparticle gap, and hence its plasmonic properties, are adjustable exclusively in the xy-plane. Thus, even though the particles are spherical, the... Read More about Self-assembly of Gold Nanoparticles into an Adjustable Plasmonic 3D Lattice using Janus-type Forked Mesogenic Ligands.

Deciphering helix assembly in the heliconical nematic phase via tender resonant X-ray scattering (2021)
Journal Article
Cao, Y., Feng, J., Nallapaneni, A., Arakawa, Y., Zhao, K., Zhang, H., …Liu, F. (2021). Deciphering helix assembly in the heliconical nematic phase via tender resonant X-ray scattering. Journal of Materials Chemistry C, 9(31), 10020-10028. https://doi.org/10.1039/d1tc02027g

Being a link between a uniaxial nematic and a chiral nematic, the twist bend nematic (NTB) has been an intriguing topic for research over the last decade as a key to understanding chirality generation. Accurate description and understanding of resona... Read More about Deciphering helix assembly in the heliconical nematic phase via tender resonant X-ray scattering.

The beauty of twist-bend nematic phase: Fast switching domains, first order fréedericksz transition and a hierarchy of structures (2021)
Journal Article
Panov, V. P., Song, J. K., Mehl, G. H., & Vij, J. K. (2021). The beauty of twist-bend nematic phase: Fast switching domains, first order fréedericksz transition and a hierarchy of structures. Crystals, 11(6), 621. https://doi.org/10.3390/cryst11060621

The twist-bend nematic phase (NTB) exhibits a complicated hierarchy of structures responsible for several intriguing properties presented here. These are: the observation of a fast electrooptic response, the exhibition of a large electroclinic effect... Read More about The beauty of twist-bend nematic phase: Fast switching domains, first order fréedericksz transition and a hierarchy of structures.

A facile synthesis of a room-temperature chiral discotic nematic liquid crystal based on pentaalkynylbenzene core (2021)
Journal Article
Yu, H., & Mehl, G. H. (in press). A facile synthesis of a room-temperature chiral discotic nematic liquid crystal based on pentaalkynylbenzene core. Liquid crystals, 1-8. https://doi.org/10.1080/02678292.2021.1900433

The preparation of discotic liquid crystal with a wide thermal nematic phase range remains a challenge. Here, a method to synthesise a class of discotic liquid crystal with exclusive and stable chiral nematic phase over a wide temperature range, base... Read More about A facile synthesis of a room-temperature chiral discotic nematic liquid crystal based on pentaalkynylbenzene core.

Electrochemically Induced Mesomorphism Switching in a Chlorpromazine Hydrochloride Lyotropic Liquid Crystal (2021)
Journal Article
Crapnell, R. D., Alhasan, H. S., Partington, L. I., Zhou, Y., Ahmed, Z., Altalhi, A. A., Varley, T. S., Alahmadi, N., Mehl, G. H., Kelly, S. M., Lawrence, N. S., Marken, F., & Wadhawan, J. D. (2021). Electrochemically Induced Mesomorphism Switching in a Chlorpromazine Hydrochloride Lyotropic Liquid Crystal. ACS Omega, 6(7), 4630-4640. https://doi.org/10.1021/acsomega.0c05284

The discovery of electrochemical switching of the Lα phase of chlorpromazine hydrochloride in water is reported. The phase is characterized using polarizing microscopy, X-ray scattering, rheological measurements, and microelectrode voltammetry. Fast,... Read More about Electrochemically Induced Mesomorphism Switching in a Chlorpromazine Hydrochloride Lyotropic Liquid Crystal.

The interplay between spatial and heliconical orientational order in twist-bend nematic materials (2021)
Journal Article
Saha, R., Feng, C., Welch, C., Mehl, G. H., Feng, J., Zhu, C., Gleeson, J. T., Sprunt, S., & Jakli, A. (2021). The interplay between spatial and heliconical orientational order in twist-bend nematic materials. Physical chemistry chemical physics : PCCP, 23(7), 4055-4063. https://doi.org/10.1039/d0cp06633h

The helical pitch formed by organic molecules, such as the α-helix of proteins, usually requires hydrogen bonding between chiral units and long-range positional order. It was recently found that certain liquid crystal oligomers can have a twist-bend... Read More about The interplay between spatial and heliconical orientational order in twist-bend nematic materials.

Molecular biaxiality determines the helical structure - infrared measurements of the molecular order in the nematic twist-bend phase of difluoro terphenyl dimer (2021)
Journal Article
Merkel, K., Loska, B., Welch, C., Mehl, G. H., & Kocot, A. (2021). Molecular biaxiality determines the helical structure - infrared measurements of the molecular order in the nematic twist-bend phase of difluoro terphenyl dimer. Physical chemistry chemical physics : PCCP, 23(7), 4151-4160. https://doi.org/10.1039/d1cp00187f

Fourier-transform infrared polarized spectroscopy was employed, to obtain the three components of the infrared absorbance for a series of bent-shaped dimers containing double fluorinated terphenyl core (DTC5Cn, n = 5, 7, 9, 11). The data were used to... Read More about Molecular biaxiality determines the helical structure - infrared measurements of the molecular order in the nematic twist-bend phase of difluoro terphenyl dimer.

The role of intermolecular interactions in stabilizing the structure of the nematic twist-bend phase (2021)
Journal Article
Merkel, K., Loska, B., Welch, C., Mehl, G. H., & Kocot, A. (2021). The role of intermolecular interactions in stabilizing the structure of the nematic twist-bend phase. RSC advances, 11(5), 2917-2925. https://doi.org/10.1039/d0ra10481g

The understanding of the relationship between molecular structure and the formation of the nematic twist-bend phase is still at an early stage of development. This is mainly related to molecular geometry, while the correlation between the nematic twi... Read More about The role of intermolecular interactions in stabilizing the structure of the nematic twist-bend phase.

Two helices from one chiral centre - self organization of disc shaped chiral nanoparticles (2020)
Journal Article
Mehl, G. H., Yu, H., Qu, W., & Liu, F. (2021). Two helices from one chiral centre - self organization of disc shaped chiral nanoparticles. Chemical science, 12(5), 1778-1782. https://doi.org/10.1039/d0sc05100d

Gold nanoparticles (AuNPs) have been prepared and surface-functionalized with a mixture of 1-hexanethiol co-ligands and chiral discogen ligands separated from a disulfide functionviaa flexible spacer. Polarized optical microscopy together with differ... Read More about Two helices from one chiral centre - self organization of disc shaped chiral nanoparticles.

A Compact Full 2π Flexoelectro‐Optic Liquid Crystal Phase Modulator (2020)
Journal Article
Wang, X., Fells, J. A. J., Shi, Y., Ali, T., Welch, C., Mehl, G. H., Wilkinson, T. D., Booth, M. J., Morris, S. M., & Elston, S. J. (2020). A Compact Full 2π Flexoelectro‐Optic Liquid Crystal Phase Modulator. Advanced Materials Technologies, 5(12), Article 2000589. https://doi.org/10.1002/admt.202000589

Wavefront shaping, which is often achieved using liquid crystal (LC) spatial light modulators, is particularly important for a wide range of applications including laser microfabrication and micromanipulation, microscopy, and quantum optics. In this... Read More about A Compact Full 2π Flexoelectro‐Optic Liquid Crystal Phase Modulator.

Chirality enhancement in macro-chiral liquid crystal nanoparticles (2020)
Journal Article
Yu, H., Welch, C., Qu, W., Schubert, C. J., Liu, F., Siligardi, G., & Mehl, G. H. (2020). Chirality enhancement in macro-chiral liquid crystal nanoparticles. Materials Horizons, 7(11), 3021-3027. https://doi.org/10.1039/d0mh01274b

The amplification of molecular chirality by metal nanoparticles (NPs) is an important and rapidly evolving field in nanomaterial research with wide applications in smart materials, catalysis, and solvent-solute interactions. Here we present the resul... Read More about Chirality enhancement in macro-chiral liquid crystal nanoparticles.

Millisecond optical phase modulation using multipass configurations with liquid-crystal devices (2020)
Journal Article
Jin, Y., Elston, S. J., Fells, J. A., Booth, M. J., Welch, C., Mehl, G. H., & Morris, S. M. (2020). Millisecond optical phase modulation using multipass configurations with liquid-crystal devices. Physical Review Applied, 14(2), Article 024007. https://doi.org/10.1103/PhysRevApplied.14.024007

We present two configurations for analog 0 to 2π optical phase modulation using liquid crystals (LCs), each of which achieve switching times that are 1 ms or less. One configuration is based on the switching behavior of a so-called nematic pi cell, a... Read More about Millisecond optical phase modulation using multipass configurations with liquid-crystal devices.

Self-Assembly and Temperature-Driven Chirality Inversion of Cholesteryl-Based Block Copolymers (2020)
Journal Article
Krishnasamy, V., Qu, W., Chen, C., Huo, H., Ramanagul, K., Gothandapani, V., Mehl, G. H., Zhang, Q., & Liu, F. (2020). Self-Assembly and Temperature-Driven Chirality Inversion of Cholesteryl-Based Block Copolymers. Macromolecules, 53(11), 4193-4203. https://doi.org/10.1021/acs.macromol.9b02264

Block copolymers (BCPs), comprising a poly(methyl methacrylate) (PMMA) block and a poly(cholesteryloxyhexyl methacrylate) (PChMA) block, were synthesized via reversible addition–fragmentation chain transfer polymerization. The self-assembly of the li... Read More about Self-Assembly and Temperature-Driven Chirality Inversion of Cholesteryl-Based Block Copolymers.

Transmissive flexoelectro-optic liquid crystal optical phase modulator with 2 π modulation (2020)
Journal Article
Wang, X., Fells, J. A. J., Ali, T., Lin, J. D., Welch, C., Mehl, G. H., Wilkinson, T. D., Booth, M. J., Morris, S. M., & Elston, S. J. (2020). Transmissive flexoelectro-optic liquid crystal optical phase modulator with 2 π modulation. AIP Advances, 10(5), Article 055011. https://doi.org/10.1063/5.0009630

© 2020 Author(s). In this paper, we demonstrate analog phase modulation in a transmissive configuration using the flexoelectro-optic effect in short-pitch chiral nematic liquid crystal (LC) devices. Two different modes are considered, both of which a... Read More about Transmissive flexoelectro-optic liquid crystal optical phase modulator with 2 π modulation.

Temperature dependence of bend elastic constant in oblique helicoidal cholesterics (2020)
Journal Article
Iadlovska, O. S., Babakhanova, G., Mehl, G. H., Welch, C., Cruickshank, E., Strachan, G. J., Storey, J. M. D., Imrie, C. T., Shiyanovskii, S. V., & Lavrentovich, O. D. (2020). Temperature dependence of bend elastic constant in oblique helicoidal cholesterics. Physical Review Research, 2(1), Article 013238. https://doi.org/10.1103/PhysRevResearch.2.013248

Elastic moduli of liquid crystals, known as Frank constants, are of quintessential importance for understanding fundamental properties of these materials and for the design of their applications. Although there are many methods to measure the Frank c... Read More about Temperature dependence of bend elastic constant in oblique helicoidal cholesterics.

Analog modulation by the flexoelectric effect in liquid crystals (2020)
Journal Article
Yip, W. C., Welch, C., Mehl, G. H., & Wilkinson, T. D. (2020). Analog modulation by the flexoelectric effect in liquid crystals. Applied optics, 59(9), 2668-2673. https://doi.org/10.1364/AO.386096

We have solved the long-standing problems of stability and hysteresis, and we are able to obtain the homogeneous uniform lying helix structure in polymer-free cholesteric liquid crystals. This is instrumental for the present work to demonstrate the a... Read More about Analog modulation by the flexoelectric effect in liquid crystals.

Probing molecular ordering in the nematic phases of para-linked bimesogen dimers through NMR studies of flexible prochiral solutes (2020)
Journal Article
Heist, L. M., Samulski, E. T., Welch, C., Ahmed, Z., Mehl, G. H., Vanakaras, A. G., & Photinos, D. J. (2020). Probing molecular ordering in the nematic phases of para-linked bimesogen dimers through NMR studies of flexible prochiral solutes. Liquid crystals, 1-16. https://doi.org/10.1080/02678292.2019.1711214

The quadrupolar splittings of perdeuteriated n-decane dissolved in nematic phases formed by mesogenic dimers of the CBnCB series, for n = 7,9,10,11, are measured throughout the entire temperature range of these phases. These results are reported toge... Read More about Probing molecular ordering in the nematic phases of para-linked bimesogen dimers through NMR studies of flexible prochiral solutes.

Macroscopic chirality of twist-bend nematic phase in bent dimers confirmed by circular dichroism (2019)
Journal Article
Stevenson, W. D., Zeng, X., Welch, C., Thakur, A. K., Ungar, G., & Mehl, G. H. (2020). Macroscopic chirality of twist-bend nematic phase in bent dimers confirmed by circular dichroism. Journal of Materials Chemistry C, 8(3), 1041-1047. https://doi.org/10.1039/c9tc05061b

Many achiral bent molecules and some polymers with such repeat units exhibit a liquid crystal phase transition between a conventional nematic (N), and a second nematic (Nx) with periodically modulated orientation. Theory predicts several possible str... Read More about Macroscopic chirality of twist-bend nematic phase in bent dimers confirmed by circular dichroism.

A cholesteric liquid crystal device having stable uniform lying helix structure (2019)
Journal Article
Yip, W. C., Welch, C., Mehl, G. H., & Wilkinson, T. D. (2020). A cholesteric liquid crystal device having stable uniform lying helix structure. Journal of Molecular Liquids, 299, Article 112141. https://doi.org/10.1016/j.molliq.2019.112141

A cholesteric liquid crystal device having the uniform lying helix (ULH) structure shows stable and reversible characteristics and it has been demonstrated for the analogue modulation in 10 micro-second response time at room temperature. The device c... Read More about A cholesteric liquid crystal device having stable uniform lying helix structure.

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