All Outputs (83)

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.

Soft modes of the dielectric response in the twist-bend nematic phase and identification of the transition to a nematic splay bend phase in the CBC7CB dimer (2019)
Journal Article
Merkel, K., Kocot, A., Mehl, G. H., & Welch, C. (2019). Soft modes of the dielectric response in the twist-bend nematic phase and identification of the transition to a nematic splay bend phase in the CBC7CB dimer. Physical chemistry chemical physics : PCCP, 21(41), 22839-22848. https://doi.org/10.1039/c9cp04952e

The dielectric spectra of the twist-bend nematic phase (NTB) of (the bent-shaped) achiral liquid-crystal dimer 1′′-,7′′-bis(4-cyanobiphenyl-4′-yl)heptane (CB7CB) are studied for the determination of the different relaxation modes. Two molecular proce... Read More about Soft modes of the dielectric response in the twist-bend nematic phase and identification of the transition to a nematic splay bend phase in the CBC7CB dimer.

Dielectric response of electric-field distortions of the twist-bend nematic phase for LC dimers (2019)
Journal Article
Merkel, K., Welch, C., Ahmed, Z., Piecek, W., & Mehl, G. H. (2019). Dielectric response of electric-field distortions of the twist-bend nematic phase for LC dimers. The Journal of chemical physics, 151(11), 114908. https://doi.org/10.1063/1.5114824

Wide band dielectric spectroscopy of bent-shaped achiral liquid-crystal dimers 1′′-n′′-bis(4-cyanobiphenyl-4′-yl) n-alkanes (CBnCB n = 7, 9, 11) has been investigated in a frequency range 0.1 Hz–100 MHz using planar-aligned cells of sample thicknesse... Read More about Dielectric response of electric-field distortions of the twist-bend nematic phase for LC dimers.

Oligomeric odd-even effect in liquid crystals (2019)
Journal Article
Saha, R., Babakhanova, G., Parsouzi, Z., Rajabi, M., Gyawali, P., Welch, C., …Jakli, A. (2019). Oligomeric odd-even effect in liquid crystals. Materials Horizons, 6(9), 1905-1912. https://doi.org/10.1039/c9mh00428a

Odd-even effects, oscillations in properties of materials comprised of an odd or even number of connected repeating units, are well-known phenomena in materials science. In organic materials, they are usually associated with the number of methylene... Read More about Oligomeric odd-even effect in liquid crystals.

Pretransitional behavior of viscoelastic parameters at the nematic to twist-bend nematic phase transition in flexible: N -mers (2019)
Journal Article
Parsouzi, Z., Babakhanova, G., Rajabi, M., Saha, R., Gyawali, P., Turiv, T., …Sprunt, S. (2019). Pretransitional behavior of viscoelastic parameters at the nematic to twist-bend nematic phase transition in flexible: N -mers. Physical chemistry chemical physics : PCCP, 21(24), 13078-13089. https://doi.org/10.1039/c9cp00984a

© 2019 the Owner Societies. We report dynamic light scattering measurements of the orientational (Frank) elastic constants and associated viscosities among a homologous series of a liquid crystalline dimer, trimer, and tetramer exhibiting a uniaxial... Read More about Pretransitional behavior of viscoelastic parameters at the nematic to twist-bend nematic phase transition in flexible: N -mers.

Dynamic response of large tilt-angle flexoelectro-optic liquid crystal modulators (2019)
Journal Article
Fells, J. A. J., Welch, C., Yip, W. C., Elston, S. J., Booth, M. J., Mehl, G. H., …Morris, S. M. (2019). Dynamic response of large tilt-angle flexoelectro-optic liquid crystal modulators. Optics express, 27(11), 15184-15193. https://doi.org/10.1364/OE.27.015184

Journal © 2019 We present here the first time-resolved tilt-angle and retardance measurements for large-tilt (>45°) flexoelectro-optic liquid crystal modulators. These devices have potential for next generation fast switching (>1 kHz), 0-2π analog ph... Read More about Dynamic response of large tilt-angle flexoelectro-optic liquid crystal modulators.

Fast and low loss flexoelectro-optic liquid crystal phase modulator with a chiral nematic reflector (2019)
Journal Article
Wang, X., Fells, J. A., Yip, W. C., Ali, T., Lin, J. D., Welch, C., …Elston, S. J. (2019). Fast and low loss flexoelectro-optic liquid crystal phase modulator with a chiral nematic reflector. Scientific reports, 9(1), Article 7016. https://doi.org/10.1038/s41598-019-42831-5

© 2019, The Author(s). In this paper, we demonstrate a flexoelectro-optic liquid crystal phase-only device that uses a chiral nematic reflector to achieve full 2π phase modulation. This configuration is found to be very tolerant to imperfections in t... Read More about Fast and low loss flexoelectro-optic liquid crystal phase modulator with a chiral nematic reflector.

Robust measurement of flexoelectro-optic switching with different surface alignments (2019)
Journal Article
Sandford O'Neill, J. J., Fells, J. A., Welch, C., Mehl, G., Yip, W. C., Wilkinson, T. D., …Morris, S. M. (2019). Robust measurement of flexoelectro-optic switching with different surface alignments. Journal of applied physics, 125(9), Article 093104. https://doi.org/10.1063/1.5086241

The alignment of chiral nematic liquid crystals in the so-called uniform lying helix geometry allows for the observation and exploitation of the flexoelectro-optic effect. However, high-quality uniform lying helix alignment is difficult to achieve re... Read More about Robust measurement of flexoelectro-optic switching with different surface alignments.

1H NMR study of molecular order and dynamics in the liquid crystal CB-C9-CB (2019)
Journal Article
Aluculesei, A., Cachitas, H., Carvalho, J., Vaca Chavez, F., Figueirinhas, J. L., Sebastião, P. J., …Mehl, G. H. (2019). 1H NMR study of molecular order and dynamics in the liquid crystal CB-C9-CB. Physical chemistry chemical physics : PCCP, 21(8), 4523-4537. https://doi.org/10.1039/c8cp06868b

© 2019 the Owner Societies. Molecular order and dynamics of the CB-C9-CB liquid crystalline dimer exhibiting the nematic (N) and the twist bend nematic (Ntb) phases were investigated by proton NMR spectroscopy, using fields of 0.78 T and 7.04 T, and... Read More about 1H NMR study of molecular order and dynamics in the liquid crystal CB-C9-CB.

Proton and Deuterium NMR study of the CBC9CB Dimer System (2019)
Journal Article
Carvalho, J., Cruz, C., Figueirinhas, J. L., Tamba, M., Kohlmeier, A., & Mehl, G. H. (2019). Proton and Deuterium NMR study of the CBC9CB Dimer System. Journal of Physical Chemistry B, 123(6), 1442-1451. https://doi.org/10.1021/acs.jpcb.8b11526

Copyright © 2019 American Chemical Society. Using proton and deuterium NMR spectroscopy, this work provides a description of the molecular orientational order of the mesogenic groups in both the N tb and the classical nematic phase (N) of the liquid... Read More about Proton and Deuterium NMR study of the CBC9CB Dimer System.

The induction of the Ntb phase in mixtures (2018)
Journal Article
Ramou, E., Welch, C., Hussey, J., Ahmed, Z., Karahaliou, P. K., & Mehl, G. H. (2018). The induction of the Ntb phase in mixtures. Liquid crystals, 45(13-15), 1929-1935. https://doi.org/10.1080/02678292.2018.1524523

We report the induction of the Ntb phase over a wide temperature and concentration range in a binary system. This was achieved by addition of a flexible dopant without LC properties to a flexible dimer exhibiting only a nematic LC phase. The Ntb phas... Read More about The induction of the Ntb phase in mixtures.

Dynamic calorimetry and XRD studies of the nematic and twist-bend nematic phase transitions in a series of dimers with increasing spacer length (2018)
Journal Article
Stevenson, W. D., Zou, H. X., Zeng, X. B., Welch, C., Ungar, G., & Mehl, G. H. (2018). Dynamic calorimetry and XRD studies of the nematic and twist-bend nematic phase transitions in a series of dimers with increasing spacer length. Physical chemistry chemical physics : PCCP, 20(39), 25268-25274. https://doi.org/10.1039/c8cp05744c

A modulated and conventional DSC study of the transitions between the twist-bend nematic (Ntb), regular nematic (N) and isotropic liquid (Iso) phases was performed on a series of difluoroterphenyl-based dimers with (CH2)n spacers; n = 5, 7, 9, 11. Th... Read More about Dynamic calorimetry and XRD studies of the nematic and twist-bend nematic phase transitions in a series of dimers with increasing spacer length.

Flexoelectro-optic liquid crystal analog phase-only modulator with a 2π range and 1 kHz switching (2018)
Journal Article
Fells, J. A., Wang, X., Elston, S. J., Welch, C., Mehl, G. H., Booth, M. J., & Morris, S. M. (2018). Flexoelectro-optic liquid crystal analog phase-only modulator with a 2π range and 1 kHz switching. Optics letters, 43(18), 4362-4365. https://doi.org/10.1364/OL.43.004362

We present a flexoelectro-optic liquid crystal (LC) analog phase modulator with >2𝜋 phase range at a 1 kHz switching frequency. The chiral nematic LC mixture consists of the bimesogen CBC7CB with chiral dopant R5011, aligned in the uniform lying heli... Read More about Flexoelectro-optic liquid crystal analog phase-only modulator with a 2π range and 1 kHz switching.

Lyotropic 'hairy' TiO2 nanorods (2018)
Journal Article
Cheng, F., Verrelli, E., Alharthi, F. A., Kelly, S. M., O'Neill, M., Kemp, N. T., …Anthopoulos, T. (2019). Lyotropic 'hairy' TiO2 nanorods. Nanoscale advances, 1(1), 254-264. https://doi.org/10.1039/c8na00054a

We report the synthesis of the first stable, solution-processable and photocrosslinkable hybrid organic/inorganic titanium dioxide nanorods as ‘hairy rods’ coated with phosphonate ligands with photoreactive coumarin groups located in a terminal posit... Read More about Lyotropic 'hairy' TiO2 nanorods.

Supramolecular organization of liquid-crystal dimers-bis-cyanobiphenyl alkanes on HOPG by scanning tunneling microscopy (2018)
Journal Article
Krzyzewska, K., Jaroch, T., Maranda-Niedbała, A., Pociecha, D., Górecka, E., Ahmed, Z., …Nowakowski, R. (2018). Supramolecular organization of liquid-crystal dimers-bis-cyanobiphenyl alkanes on HOPG by scanning tunneling microscopy. Nanoscale, 10(34), 16201-16210. https://doi.org/10.1039/c8nr02069h

2D supramolecular organization of a series of six cyanobiphenyl bimesogens deposited on highly oriented pyrolytic graphite (HOPG) is studied by scanning tunneling microscopy (STM). The adsorbates are 1,ω-bis(4-cyanobiphenyl-4’-yl)alkanes (CBnCB) with... Read More about Supramolecular organization of liquid-crystal dimers-bis-cyanobiphenyl alkanes on HOPG by scanning tunneling microscopy.

EPR study of the polydomain structure of the twist-bend nematic phase of CB9CB in the bulk (2018)
Journal Article
Bacchiocchi, C., Tamba, M., Mehl, G. H., Arcioni, A., Miglioli, I., & Zannoni, C. (2018). EPR study of the polydomain structure of the twist-bend nematic phase of CB9CB in the bulk. Liquid crystals, 45(13-15), 2109-2120. https://doi.org/10.1080/02678292.2018.1501110

EPR spin probe spectra of the liquid crystal phases exhibited, in the bulk, by the 1″,9″-bis(4- cyanobiphenyl-4’-yl)nonane (CB9CB) bent-shape dimer showed that, on cooling from the isotropic phase, this material forms a uniaxial nematic phase with a... Read More about EPR study of the polydomain structure of the twist-bend nematic phase of CB9CB in the bulk.

Characterization of large tilt-angle flexoelectro-optic switching in chiral nematic liquid crystal devices (2018)
Journal Article
Wang, X., Fells, J. A. J., Welch, C., Tamba, M., Mehl, G. H., Morris, S. M., & Elston, S. J. (2019). Characterization of large tilt-angle flexoelectro-optic switching in chiral nematic liquid crystal devices. Liquid crystals, 46(3), 408-414. https://doi.org/10.1080/02678292.2018.1502822

The “flexoelastic ratio”, which is the ratio of the effective flexoelectric coefficient to the elastic coefficients, is commonly used to characterize the electro-optic behavior of chiral nematic liquid crystal (LC) devices that exhibit flexoelectro-o... Read More about Characterization of large tilt-angle flexoelectro-optic switching in chiral nematic liquid crystal devices.

Tuning selective reflection of light by surface anchoring in cholesteric cells with oblique helicoidal structures (2018)
Journal Article
Iadlovska, O. S., Maxwell, G. R., Babakhanova, G., Mehl, G. H., Welch, C., Shiyanovskii, S. V., & Lavrentovich, O. D. (2018). Tuning selective reflection of light by surface anchoring in cholesteric cells with oblique helicoidal structures. Optics letters, 43(8), 1850-1853. https://doi.org/10.1364/ol.43.001850

Selective reflection of light by oblique helicoidal cholesteric (ChOH) can be tuned in a very broad spectral range by an applied electric field. In this work, we demonstrate that the peak wavelength of the selective reflection can be controlled by su... Read More about Tuning selective reflection of light by surface anchoring in cholesteric cells with oblique helicoidal structures.

Characterization of the Submicrometer Hierarchy Levels in the Twist-Bend Nematic Phase with Nanometric Helices via Photopolymerization. Explanation for the Sign Reversal in the Polar Response (2017)
Journal Article
Panov, V. P., Sreenilayam, S. P., Panarin, Y. P., Vij, J. K., Welch, C. J., & Mehl, G. H. (2017). Characterization of the Submicrometer Hierarchy Levels in the Twist-Bend Nematic Phase with Nanometric Helices via Photopolymerization. Explanation for the Sign Reversal in the Polar Response. Nano Letters, 17(12), 7515-7519. https://doi.org/10.1021/acs.nanolett.7b03441

Photopolymerization of a reactive mesogen mixed with a mesogenic dimer, shown to exhibit the twist-bend nematic phase (NTB), reveals the complex structure of the self-deformation patterns observed in planar cells. The polymerized reactive mesogen ret... Read More about Characterization of the Submicrometer Hierarchy Levels in the Twist-Bend Nematic Phase with Nanometric Helices via Photopolymerization. Explanation for the Sign Reversal in the Polar Response.