High speed multi-level phase device for active spatial control

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.

Dipole-dipole correlations in the nematic phases of symmetric cyanobiphenyl dimers and their binary mixtures with 5CB (2023)
Journal Article
Zavvou, E. E., Ramou, E., Ahmed, Z., Welch, C., Mehl, G. H., Vanakaras, A. G., & Karahaliou, P. K. (2023). Dipole-dipole correlations in the nematic phases of symmetric cyanobiphenyl dimers and their binary mixtures with 5CB. Soft matter, 19(47), 9224-9238. https://doi.org/10.1039/d3sm01017a

We report on the temperature dependence of birefringence and of the static dielectric permittivity tensor in a series of binary mixtures between the symmetric, bent-shaped, 1′′,9′′-bis(4-cyanobiphenyl-4′-yl)nonane (CB9CB) dimer and the monomeric nema... Read More about Dipole-dipole correlations in the nematic phases of symmetric cyanobiphenyl dimers and their binary mixtures with 5CB.

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 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.-G., 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.

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., Welch, C., Mehl, G. H., Proń, A., & 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.

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.

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., Mehl, G. H., Booth, M. J., Wilkinson, T. D., Morris, S. M., & 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.

Oligomeric odd-even effect in liquid crystals (2019)
Journal Article
Saha, R., Babakhanova, G., Parsouzi, Z., Rajabi, M., Gyawali, P., Welch, C., Mehl, G. H., Gleeson, J. T., Lavrentovich, O. D., Sprunt, S., & 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.

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.