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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, 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.

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, 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.

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

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 phase spatial lig... 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. J., Yip, W. C., Ali, T., Lin, J., Welch, C., …Elston, S. J. (2019). Fast and low loss flexoelectro-optic liquid crystal phase modulator with a chiral nematic reflector. Scientific reports, 9, 1-8. https://doi.org/10.1038/s41598-019-42831-5

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 the chiral nematic refle... Read More about Fast and low loss flexoelectro-optic liquid crystal phase modulator with a chiral nematic reflector.

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

In this paper, we demonstrate a flexoelectro-optic liquid crystal phase-only device that uses a chiral nematic reflector to achieve full 2 pi  phase modulation. This configuration is found to be very tolerant to imperfections in the chiral nematic r... Read More about Fast and low loss flexoelectro-optic liquid crystal phase modulear with a chiral nematic reflector.

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.

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.

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. doi: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.

Characterization of the sub-micrometer 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 sub-micrometer 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. doi: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 sub-micrometer hierarchy levels in the twist-bend nematic phase with nanometric helices via photopolymerization. Explanation for the sign reversal in the polar response.

Molecular organization in the twist–bend nematic phase by resonant X-ray scattering at the Se K-edge and by SAXS, WAXS and GIXRD (2017)
Journal Article
Stevenson, W. D., Ahmed, Z., Zeng, X. B., Welch, C., Ungar, G., & Mehl, G. H. (2017). Molecular organization in the twist–bend nematic phase by resonant X-ray scattering at the Se K-edge and by SAXS, WAXS and GIXRD. Physical chemistry chemical physics : PCCP, 19(21), 13449-13454. https://doi.org/10.1039/c7cp01404j

© the Owner Societies 2017. Using a magnetically aligned liquid crystal mixture containing a novel Se-labelled dimer and the difluoroterphenyl dimer DTC5C7, the twist-bend nematic phase (N tb ) was studied by the resonant scattering of hard X-rays an... Read More about Molecular organization in the twist–bend nematic phase by resonant X-ray scattering at the Se K-edge and by SAXS, WAXS and GIXRD.

Light scattering study of the “pseudo-layer” compression elastic constant in a twist-bend nematic liquid crystal (2016)
Journal Article
Parsouzi, Z., Pardaev, S. A., Welch, C., Ahmed, Z., Mehl, G. H., Baldwin, A. R., …Sprunt, S. (2016). Light scattering study of the “pseudo-layer” compression elastic constant in a twist-bend nematic liquid crystal. Physical chemistry chemical physics : PCCP, 18(46), 31645-31652. https://doi.org/10.1039/C6CP06292J

The nematic twist-bend (TB) phase, exhibited by certain achiral thermotropic liquid crystalline (LC) dimers, features a nanometer-scale, heliconical rotation of the average molecular long axis (director) with equally probable left- and right-handed d... Read More about Light scattering study of the “pseudo-layer” compression elastic constant in a twist-bend nematic liquid crystal.

Comparative analysis of anisotropic material properties of uniaxial nematics formed by flexible dimers and rod-like monomers (2016)
Journal Article
Cukrov, G., Mosaddeghian Golestani, Y., Xiang, J., Nastishin, Y. A., Ahmed, Z., Welch, C., …Lavrentovich, O. D. (2017). Comparative analysis of anisotropic material properties of uniaxial nematics formed by flexible dimers and rod-like monomers. Liquid crystals, 44(1), 219-231. https://doi.org/10.1080/02678292.2016.1240248

We report temperature dependencies of material properties such as dielectric anisotropy, birefringence, splay (K₁₁), twist (K₂₂), and bend (K₃₃) elastic constants of the uniaxial nematic (N) phase formed by flexible dimers of DTC5C9 and compare their... Read More about Comparative analysis of anisotropic material properties of uniaxial nematics formed by flexible dimers and rod-like monomers.

Deuteron and proton NMR study of D₂, p-dichlorobenzene and 1,3,5-trichlorobenzene in bimesogenic liquid crystals with two nematic phases (2016)
Journal Article
Burnell, E. E., Ahmed, Z., Welch, C., Mehl, G. H., & Dong, R. Y. (2016). Deuteron and proton NMR study of D₂, p-dichlorobenzene and 1,3,5-trichlorobenzene in bimesogenic liquid crystals with two nematic phases. Chemical Physics Letters, 659, 48-54. doi:10.1016/j.cplett.2016.07.005

The solutes dideuterium, 1,3,5-trichlorobenzene and p-dichlorobenzene (pdcb) are co-dissolved in a 61/39 wt% mixture of CBC9CB/5CB, a bimesogenic liquid crystal with two nematic phases. NMR spectra are collected for each solute. The local electric fi... Read More about Deuteron and proton NMR study of D₂, p-dichlorobenzene and 1,3,5-trichlorobenzene in bimesogenic liquid crystals with two nematic phases.

Mesophase structure and behaviour in bulk and restricted geometry of a dimeric compound exhibiting a nematic-nematic transition (2016)
Journal Article
Sebastián, N., Tamba, M. G., Stannarius, R., de la Fuente, M. R., Salamonczyk, M., Cukrov, G., …Eremin, A. (2016). Mesophase structure and behaviour in bulk and restricted geometry of a dimeric compound exhibiting a nematic-nematic transition. Physical chemistry chemical physics : PCCP, 18(28), 19299-19308. doi:10.1039/c6cp03899a

We present structural studies of a dimeric compound composed of a central heptyl spacer linking two mesogens consisiting of terphenyl units at which two adjacent fluoro groups are attached to each central ring. The terminal rings are linked to pentyl... Read More about Mesophase structure and behaviour in bulk and restricted geometry of a dimeric compound exhibiting a nematic-nematic transition.

Fluctuation modes of a twist-bend nematic liquid crystal (2016)
Journal Article
Parsouzi, Z., Shamid, S. M., Borshch, V., Challa, P. K., Baldwin, A. R., Tamba, M. G., …Sprunt, S. (2016). Fluctuation modes of a twist-bend nematic liquid crystal. Physical Review X, 6(2), 021041-1-021041-16. https://doi.org/10.1103/PhysRevX.6.021041

We report a dynamic light-scattering study of the fluctuation modes in a thermotropic liquid crystalline mixture of monomer and dimer compounds that exhibits the twist-bend nematic (NTB) phase. The results reveal a spectrum of overdamped fluctuations... Read More about Fluctuation modes of a twist-bend nematic liquid crystal.

Anomalous increase in nematic-isotropic transition temperature in dimer molecules induced by magnetic field (2016)
Journal Article
Salili, S. M., Tamba, M. G., Sprunt, S. N., Welch, C., Mehl, G. H., Jákli, A., & Gleeson, J. T. (2016). Anomalous increase in nematic-isotropic transition temperature in dimer molecules induced by magnetic field. Physical review letters, 116(21-27 May), https://doi.org/10.1103/PhysRevLett.116.217801

We have determined the nematic-isotropic transition temperature as a function of applied magnetic field in three different thermotropic liquid crystalline dimers. These molecules are comprised of two rigid calamitic moieties joined end to end by flex... Read More about Anomalous increase in nematic-isotropic transition temperature in dimer molecules induced by magnetic field.

Second harmonic light scattering induced by defects in the twist-bend nematic phase of liquid crystal dimers (2016)
Journal Article
Pardaev, S. A., Shamid, S. M., Tamba, M. G., Welch, C., Mehl, G. H., Gleeson, J. T., …Sprunt, S. (2016). Second harmonic light scattering induced by defects in the twist-bend nematic phase of liquid crystal dimers. Soft matter, 12(19), 4472-4482. doi:10.1039/c6sm00585c

The nematic twist-bend (NTB) phase, exhibited by certain thermotropic liquid crystalline (LC) dimers, represents a new orientationally ordered mesophase -- the first distinct nematic variant discovered in many years. The NTB phase is distinguished by... Read More about Second harmonic light scattering induced by defects in the twist-bend nematic phase of liquid crystal dimers.


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