All Outputs (36)

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.

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.

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.

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.

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.

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.

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.

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., Wang, H., Baldwin, A., Welch, C., Mehl, G. H., Gleeson, J. T., Jakli, A., Lavrentovich, O. D., & 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., Wilkinson, T. D., & 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., 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.

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.

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.

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.

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.

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.