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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., …Liu, F. (in press). Self-Assembly and Temperature-Driven Chirality Inversion of Cholesteryl-Based Block Copolymers. Macromolecules, 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 2π modulation (2020)
Journal Article
Wang, X., Fells, J. A. J., Ali, T., Lin, J., Welch, C., Mehl, G. H., …Elston, S. J. (2020). Transmissive flexoelectro-optic liquid crystal optical phase modulator with 2π modulation. AIP Advances, 10(5), https://doi.org/10.1063/5.0009630

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 are shown to genera... Read More about Transmissive flexoelectro-optic liquid crystal optical phase modulator with 2π 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., …Shiyanovskii, S. V. (2020). Temperature dependence of bend elastic constant in oblique helicoidal cholesterics. Physical Review Research, 2(1), 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... Read More about Temperature dependence of bend elastic constant in oblique helicoidal cholesterics.

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. (in press). 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, 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., 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, 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 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 nematic splay bend phase in the CBC7CB dimer. Physical chemistry chemical physics : PCCP, 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 proces... Read More about Soft modes of the dielectric response in the twist-bend nematic phase and identification of the transition to 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, 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.

Robust measurement of flexoelectro-optic switching with different surface alignments (2019)
Journal Article
Sandford O’Neill, J. J., Fells, J. A. J., 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), 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 CBC9CB Liquid Crystal (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 CBC9CB Liquid Crystal. Physical chemistry chemical physics : PCCP, 21(8), 4523-4537. https://doi.org/10.1039/c8cp06868b

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 0.78T and 7.04T, and relaxometry. The first relaxom... Read More about 1H NMR study of molecular order and dynamics in CBC9CB Liquid Crystal.

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

Using proton and deuterium NMR spectroscopy , this work provides a description of the molecular order of the mesogenic grops in both the Ntb and the classical nematic phase (N), of the liquid crystal dimer CB-C9CB. The proton NMR data were collected... 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., Zeng, X., 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, 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.

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.


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